Rockbox Technical Forums

Rockbox Development => Feature Ideas => Topic started by: FaN on February 22, 2012, 07:15:10 AM

Title: Battery management while charging
Post by: FaN on February 22, 2012, 07:15:10 AM
Hello ROCKbox world,

I'm new on this forum, and a new user of this awesome FW, and I'm already loving it!
I've got a Iaudio M3 and a Sansa Clip +, both rockboxed, and both have the same king of usage which is probably not so frequent: I'm listening to MP3 at work, and thus, the player is continuously connected to USB to charge.
And thus, the battery is always fully charged...
On my M3, I've used 3 batteries: all dead with only a few charge/discharge cycles, because it stays always at 100% SOC (State Of Charge).

In order to maximize the battery life, it could be very great to have the opportunity to select a 'connected mode'.
1. normal mode, to charge the battery in order to use the player in a normal way.
2. desk mode, on which the SOC target could be set to @40%, in order to preserve the battery.

Is this something that could be done?

Thanks for all the job done so far,
/Vincent
Title: Re: Battery management while charging
Post by: saratoga on February 22, 2012, 11:56:39 AM
I doubt its going to make much difference to keep the battery less charged.
Title: Re: Battery management while charging
Post by: bertrik on February 22, 2012, 12:13:23 PM
At least on the Clip+, charging stops when the battery gets fully charged, even when connected to a PC. After that you have to replug it to start a new charge cycle.

Actually I can imagine having a battery life extension option, my netbook has one (Samsung N510). In battery extension mode, it charges only up to 80% instead of 100%. In the short term, I don't think we'll see any such option on rockbox yet.
Title: Re: Battery management while charging
Post by: pabouk on February 23, 2012, 10:00:14 AM
It is a known fact that Li-ion and Li-Pol batteries age faster when they are more charged and/or when their temperature is higher. So option to stop charging at certain level and possibly to not start charging when the charge is above certain level would be useful.

Dependency of aging on the number of charge cycles is not clear but from my experience it seems that avoiding large number of partial charges makes the life of a battery longer.
Title: Re: Battery management while charging
Post by: torne on February 23, 2012, 11:27:16 AM
It *is* true, however it doesn't matter very much. It's only a big deal when the battery is stored for a long time without being used. If you're actually using the player every couple of days then it's not going to spend long enough fully charged for it to make a lot of difference to the battery's lifetime.

In general, for real devices that users use every day, you can do anything you like when you charge it (charge it often or not, fully or not, leave it plugged in when charged or not) and the result will be absolutely no observable difference whatsoever. This really only matters for things that are infrequently used.
Title: Re: Battery management while charging
Post by: dreamlayers on February 24, 2012, 01:39:30 AM
If you have long battery life and you plug in the player daily (eg. in a car or playing music via a dock at home), then the battery will probably spend most of its time near full charge and wear out sooner. It would be nice to have a charging level limit for such situations.

There should be some hysteresis. (The level required to re-start charging should be a few percentage points below the level that ends it.) This should also exist in the normal case, when charging to 100%.

Even without this, the battery should still last for a few years. If it dies after a few charge/discharge cycles, then it was probably defective, low quality or abused in more serious ways.

I don't think it makes sense to worry much about battery level micro-management, but the point here is that it's a feature you can simply set and leave until you need more capacity.
Title: Re: Battery management while charging
Post by: FaN on February 24, 2012, 02:57:15 AM
Hello,

Thanks a lot for all your feedbacks!
I'm working with lithium batteries, and using LiPo in remote controlled cars, and i can tell you that the extreme charge/discharge levels are bad for battery life.

For example, in hybrid vehicles with LiIon batteries, the usefull range of SoC et 30-60%.
When driver see 0%, the real level is 30, and when fully charged on dasboard, real charge is 60%!
Title: Re: Battery management while charging
Post by: bertrik on February 24, 2012, 05:05:55 AM
What would be a reasonable way to charge to a lesser extent?
Just adjust the max. charge voltage to a lower value (and keep the current settings the same)?

As far as I've seen with many Sansa players, the useful voltage range during use is from about 4.1V to about 3.6V, or a range of 0.5V.
Currently we charge with a voltage limit at 4.2V, so would charging up to 4.1V to get at 80% (for example) with the same current settings be reasonable?
Title: Re: Battery management while charging
Post by: torne on February 24, 2012, 06:13:47 AM
I'm working with lithium batteries, and using LiPo in remote controlled cars, and i can tell you that the extreme charge/discharge levels are bad for battery life.

For example, in hybrid vehicles with LiIon batteries, the usefull range of SoC et 30-60%.
When driver see 0%, the real level is 30, and when fully charged on dasboard, real charge is 60%!
RC cars, and real cars, have drastically different load characteristics to portable consumer electronics. The effect really is a lot less than you think. :)
Title: Re: Battery management while charging
Post by: FaN on February 24, 2012, 06:27:36 AM
Why not introduce a parameter to select the balance between Autonomy vs battery life?
For instance:
Autonomy: SoC in range 3.6 - 4.2V
Battery life: SoC in range 3.7 - 4.0V
This is just a suggestion of values, it needs to be discussed. But I like the balance parameter. It's easy to set for the user, and a good way to adjust according to everybody needs’.

I'd like to add one remark: I was wondering why I've never seen any Li-based device having this kind of parameter. But is i quite obvious: for manufacturer, the only interest in battery management is to show that a brand new device has a big autonomy. If the battery life is short, it's even a plus, as the customer will buy a new one!
End of parenthesis, sorry.

Interesting stuffs there:
http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries (http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries)
Abstract:
Li-ion does not need to be fully charged, as is the case with lead acid, nor is it desirable to do so. In fact, it is better not to fully charge, because high voltages stresses the battery. Choosing a lower voltage threshold, or eliminating the saturation charge altogether, prolongs battery life but this reduces the runtime. Since the consumer market promotes maximum runtime, these chargers go for maximum capacity rather than extended service life.

What king of charge is used in Sansa? Do we complete a full charge with a small current? Or do we stop as soon as the voltage reach the target?
Could we also play with this?

torne has replied before me...
Could you explain the differences please?
Or provide a link about this?

Title: Re: Battery management while charging
Post by: torne on February 24, 2012, 11:45:58 AM
It comes down to this: there's two (main) things that reduce the capacity of a battery: the passage of time, and recharging it. A battery that's just sitting around doing nothing will lose capacity no matter what; the rate depends on temperature and on the level of charge, and indeed it will lose capacity faster if it's left fully charged. However, you're going to kill the battery in your consumer electronics through repeated charge cycles long before you notice this effect.

RC cars typically aren't actually used very often; they spend days, weeks or months at a time sitting on a shelf. Mine has certainly had less than a hundred charge cycles *ever* :) This means that the capacity loss is dominated by how much it's lost over time, and thus it's important not to leave it fully charged when you put it on that shelf.

Actual hybrid cars switch between charging and discharging on an extremely frequent basis, often second-by-second, with a load that varies even faster, and then on top of that *also* get left sitting around for long periods without any consideration to their state of charge when doing so. This is basically the worst treatment you can give a battery and any attempt to make it last longer is subject to a zillion variables that hopefully your car manufacturer understands, but you probably don't :)

My smartphone, for a different example, can chew its entire battery from 100% to 0% in about 20 hours if I use it as much as I normally do. I end up charging it multiple times per day as a result. Even then, it's not fully charged for a very large proportion of the time, and the number of charge cycles massively outweighs the loss-over-time effect.

An MP3 player is not quite so bad, hopefully, since they are not usually turned on 24/7 and their power consumption even when in use is lower compared to their battery size, but they are much closer to the smartphone example than the RC car example.

If your MP3 player lasts long enough on a single charge that you can use it for several days without charging it, then it's very likely that the best *simple* thing to do in terms of preserving its battery lifetime is just to.. use it several days without charging it. When you think it's too low to go another day without charging it, charge it. The difference between letting it charge to 100% and letting it charge to a lower voltage is pretty minor compared to just not charging it as often. :)

Anyway, if you feel like writing a patch to control charging behaviour in this way, then go for it; I'm just noting that the effect is likely to be much smaller than you imagine, and may in fact be unmeasurable.
Title: Re: Battery management while charging
Post by: FaN on February 26, 2012, 11:48:16 AM
I understand, and you're probably right.
so... I don't know if such a patch could correct my problem. Probably not...

But... I'm convinced it can be great for other users, with other kind of usage of their players...

Not sure...

Don't know what to think about!  ???
Title: Re: Battery management while charging
Post by: blr_p on October 20, 2012, 04:17:20 PM
However, you're going to kill the battery in your consumer electronics through repeated charge cycles long before you notice this effect.
I'd like to know the basis for why you say repeated charge cycles will kill the battery.

From BU (http://batteryuniversity.com/learn/article/battery_performance_as_a_function_of_cycling), the detrimental effect is marginal wrt to charging li-ion/poly ceterius paribus.

(http://batteryuniversity.com/_img/content/cycle4.jpg)

Normal charging should only get a Li-ion lukewarm. Whats more dangerous (http://batteryuniversity.com/learn/article/how_to_charge_when_to_charge_table)  is fast charging and harsh discharges. Think super fast wall chargers and deep discharges.


If your MP3 player lasts long enough on a single charge that you can use it for several days without charging it, then it's very likely that the best *simple* thing to do in terms of preserving its battery lifetime is just to.. use it several days without charging it. When you think it's too low to go another day without charging it, charge it. The difference between letting it charge to 100% and letting it charge to a lower voltage is pretty minor compared to just not charging it as often. :)
If you go several days without charging and then charge when it is too low, then you have to deal with a higher DoD (Depth of Discharge)  See Table 2 here (http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries)

The smaller the DoD the better. That means frequent charges with small DoD is better than less frequent charges with a larger DoD. Temps are lower with partial charges than longer ones. And we all know elevated temp is the biggest battery killer.

The reason i posted here is I am in agreement that RB needs a feature that allows the user to set the max charging level or voltage. Going with Table 4 of the previous posted link that is at 3.9 - 4.0V.

3.9V corresponds to 70% using this battery benchmark log (http://www.rockbox.org/wiki/pub/Main/SansaRuntime/battery_bench_Clip_8-22-10.txt) .

Therefore the optimal charging level is not 100% but rather closer to 70% (or whatever the corresponding voltage). If there was way to stop charging at that level via a user configurable setting then battery life could be improved considerably.

The magic formula for li-poly battery longevity is...

charge to 70%, use till down to 45% and then recharge again.

This provides a low DoD of just 25% and keeps battery stress to a minimum.

The runtime is reduced to ~4 hours ( in the case of the Clip+) but that is a decent duration between recharges.


Anyway, if you feel like writing a patch to control charging behaviour in this way, then go for it; I'm just noting that the effect is likely to be much smaller than you imagine, and may in fact be unmeasurable.
Heh, no, i cannot do this. I've posted to stimulate a discussion and hopefully generate interest in allowing such a feature into RB. Way i see it it such a feature will benefit any portable li-poly device RB is installed on to the tune of 2-3x longer battery life if BU's figures are correct.

I absolutely detest how i have to throw out a much loved device because its impossible for the user to change the battery  ::)

Quote from: FaN
I was wondering why I've never seen any Li-based device having this kind of parameter. But is i quite obvious: for manufacturer, the only interest in battery management is to show that a brand new device has a big autonomy. If the battery life is short, it's even a plus, as the customer will buy a new one!
Because the consumer wants a device that will run the longest. Run time is more important than battery longevity.
Title: Re: Battery management while charging
Post by: saratoga on October 20, 2012, 08:01:42 PM
If batteries are really good for so many charge cycles as that chart suggests then I don't think this setting makes sense.
Title: Re: Battery management while charging
Post by: torne on October 21, 2012, 12:29:07 PM
The information you link to does not support your conclusions (in fact, they agree with me) :)
Title: Re: Battery management while charging
Post by: blr_p on October 21, 2012, 03:00:53 PM
The information you link to does not support your conclusions (in fact, they agree with me) :)
How so ?

Post Merge: October 21, 2012, 03:02:51 PM
If batteries are really good for so many charge cycles as that chart suggests then I don't think this setting makes sense.
You get as many cycles only if you take care of the batteries.
Title: Re: Battery management while charging
Post by: saratoga on October 21, 2012, 03:24:32 PM
1000 100% charge cycles with basically no loss of capacity suggests that shallow discharging isn't really useful. 
Title: Re: Battery management while charging
Post by: blr_p on October 22, 2012, 06:49:39 AM
Ah but the first chart does not say anything about how charging was performed. The assumption is the batteries were placed in an analyser and charged/discharged repeatedly. The point of the chart was to rebut torne's assertion that charging per se is detrimental.

The basis on which he made that statement still remains outstanding.

Also why do the BU docs take the trouble to explain in the Li-ion sectoin HOW the charging should be done to preserve battery life. These later points are what i've highlighted, and are all linked in my first post.

You want to comment on them ?  ;)

My goal here is to establish the concept that not charging to 100% and partial charges are better than charging to 100% and letting the unit run flat.

This is what a company whose bussines it is to test batteries has to say. Anyone who wants to counter that with sources of their own, go ahead. But general disagreement isn't really refuting what i've said , quite the contrary.
Title: Re: Battery management while charging
Post by: torne on October 22, 2012, 08:41:16 AM
Ah but the first chart does not say anything about how charging was performed. The assumption is the batteries were placed in an analyser and charged/discharged repeatedly. The point of the chart was to rebut torne's assertion that charging per se is detrimental.
The *chart* doesn't, but the article that contains it does indeed say that it's referring to full discharge/full recharge cycles. Also, the chart shows capacity dropping off with number of charges.. so it doesn't rebut my claim at all.

Quote
The basis on which he made that statement still remains outstanding.

Also why do the BU docs take the trouble to explain in the Li-ion sectoin HOW the charging should be done to preserve battery life. These later points are what i've highlighted, and are all linked in my first post.

You want to comment on them ?  ;)
I never disagreed with any of the things BU claim; I just noted that they don't make much measurable difference with batteries in regular consumer electronics, and that therefore it's probably a waste of time to implement a more complex charging scheme that gives people less runtime.

Quote
My goal here is to establish the concept that not charging to 100% and partial charges are better than charging to 100% and letting the unit run flat.
I never said it wasn't, just that it's not very important. Please read more carefully.
Title: Re: Battery management while charging
Post by: torne on October 22, 2012, 08:49:25 AM
I think the point you're missing is that if your suggested regimen is to charge to 70% and then only let it discharge down to 45%, you are throwing away a huge amount of your runtime *anyway*. In a couple of years time, your battery will probably be in better condition than someone who hasn't done that, but you haven't *gained anything* by doing so: their battery, even used randomly for the same length of time, probably has more 100-0% runtime than yours does 70-45% runtime :)

My ipodvideo's battery has not been replaced since the device was made in 2006, was used by someone else before me, and neither I nor the previous owner took any care over its battery whatsoever. When I got it halfway through its life, it lasted for 22-23 hours; it now lasts for 21-22 hours. If I only used it 70%-45% then even with a brand new battery I'd get way less runtime.
Title: Re: Battery management while charging
Post by: saratoga on October 22, 2012, 12:04:03 PM
Ah but the first chart does not say anything about how charging was performed. The assumption is the batteries were placed in an analyser and charged/discharged repeatedly. The point of the chart was to rebut torne's assertion that charging per se is detrimental.

The basis on which he made that statement still remains outstanding.

Also why do the BU docs take the trouble to explain in the Li-ion sectoin HOW the charging should be done to preserve battery life. These later points are what i've highlighted, and are all linked in my first post.

You want to comment on them ?  ;)

The charge conditions are actually explained if you read the article.  As for why your links seem to contradict each other, its probably because some of them are specific to individual battery models or testing procedures and cannot be generalized otherwise (e.g. they do not apply to mp3 players).

If you figure it out, feel free to update this thread.

My goal here is to establish the concept that not charging to 100% and partial charges are better than charging to 100% and letting the unit run flat.

Well, you've done the opposite.  I guess if you find more data, you could try and make a better argument.  Otherwise, it seems like this isn't worthwhile. 
Title: Re: Battery management while charging
Post by: blr_p on October 22, 2012, 03:39:55 PM
The *chart* doesn't, but the article that contains it does indeed say that it's referring to full discharge/full recharge cycles. Also, the chart shows capacity dropping off with number of charges.. so it doesn't rebut my claim at all.
You're right it says full discharge/recharge and we see capacity dropping with number of cycles. But you are also ignoring that it is the full discharges that are the result of lower capacity.

The charging per se is not responsible for lower capacity. I've found nothing in the BU docs to substantiate that normal charging is detrimental to a li-ion batterys capacity.

Now consider the second link (http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries)

This chart was used with smartphone batteries, those batteries as close as you get to mp3 players, however their load is very different. So you could probably double the cycles for a PMP.

The point here is again that full discharges negatively affect battery life as that is exactly how these batterys were discharged.

(http://batteryuniversity.com/_img/content/lithium1.jpg)

Within the context of that graph the advice is offered against larger DoD and Charging level. The difference in cycles is almost fourfold with better management.

I never disagreed with any of the things BU claim; I just noted that they don't make much measurable difference with batteries in regular consumer electronics, and that therefore it's probably a waste of time to implement a more complex charging scheme that gives people less runtime.
How do you know that they don't make a difference ?

The above graph leads me to think otherwise and the advice offered below the graph on the linked page supports it.

Had i not read the BU docs i would not even realise that it matters not to charge to 100%. This is why i started searching the board and to my pleasant surprise found that somebody else had already earlier mentioned the same.


Post Merge: October 22, 2012, 03:59:33 PM
I think the point you're missing is that if your suggested regimen is to charge to 70% and then only let it discharge down to 45%, you are throwing away a huge amount of your runtime *anyway*.
Sure, but the idea is to foster a best practice. Articulating that best practice needs to be done. Does not have to be 70%, you can go upto 80% and bag an extra hour or more of runtime, 70% is less damaging than 80 which in turn is less damaging than 90 or 100.

Throwing away is an exaggeration, i'm choosing not to use it, but the battery can still deliver it as opposed to being unable to. For me ~4 hrs/session is good enough. For those that need more time they need to get a player with a battery with more capacity than 15h to begin with. Its a sizing issue, ideally a player that can deliver 3-4 times what you need is better.

An extra point is that of parasitic loads, charging a device while its still on tends to trick the guage into taking more charge. Now switching off the device isn't an option while charging it, so accepting a lower charge is safer than 100%

It does not mean you do it all the time, there may be times when you need more run time. But if such a regimen is followed regularly the idea is you hold onto your player longer than otherwise.

Its very difficult to know how long these batteries last because there are many variables involved, care, temperature, load, frequency of use etc.  Just because you got so much time does not mean the same will apply to me or if you got much less time either. So the next question is what do i do so it lasts the longest.

If this was a cell phone i would not be bothered at all as i could replace the battery myself.

In a couple of years time, your battery will probably be in better condition than someone who hasn't done that, but you haven't *gained anything* by doing so: their battery, even used randomly for the same length of time, probably has more 100-0% runtime than yours does 70-45% runtime :)
I don't follow what you're saying here.

According to BU's docs, after a couple of years charging to 100% is worse than with brand new.

A person that charged to 100% and used it with full DoD has got more run time out of the player, whereas i've deferred my use of it. But if they need more run time their battery isn't going to be up to it, mine will.

My ipodvideo's battery has not been replaced since the device was made in 2006, was used by someone else before me, and neither I nor the previous owner took any care over its battery whatsoever. When I got it halfway through its life, it lasted for 22-23 hours; it now lasts for 21-22 hours. If I only used it 70%-45% then even with a brand new battery I'd get way less runtime.
How do you know the battery actually has this much life on it. Do you run battery benchmarks on it regularly ?

The guage always goes to the top but the actual runtime can be a different story with the guage dropping faster than expected.

There is another point here, your's is an anecdotal experience versus testing data by a battery company. I'm more inclinced to give the latter the benefit of the doubt.

An ipod has got better battery life to start with than a clip+ which maxes out at 15 hours and i've got very attached to it & RB.

The BU docs say its good to do a calibration every 40 partial charges, if you use it everyday thats once a month. I prefer to do it once very 3 months. Not too bothered if the guage goes out of sync by even 10% in that time so long as i know the battery is still going strong.

FWIW i've found pulling the clip+ after a half hour gets me to about the right level.
Title: Re: Battery management while charging
Post by: torne on October 23, 2012, 04:38:23 AM
The charging per se is not responsible for lower capacity. I've found nothing in the BU docs to substantiate that normal charging is detrimental to a li-ion batterys capacity.
Then maybe you need to go read more about battery chemistry rather than just relying on a single source? It is a fundamental fact of every battery technology that we have that they degrade with use no matter what you do with them. There is no free lunch. Usage pattern can change the rate of degradation, but nothing is going to stop it.

You keep repeating yourself explaining the same things that I'm not even contesting over and over, so that's getting kinda dull. :)

Quote
Throwing away is an exaggeration, i'm choosing not to use it, but the battery can still deliver it as opposed to being unable to. For me ~4 hrs/session is good enough. For those that need more time they need to get a player with a battery with more capacity than 15h to begin with. Its a sizing issue, ideally a player that can deliver 3-4 times what you need is better.
This just doesn't make any logical sense. If 4 hours a session is good enough for you and the full capacity of the battery is 15 hours of runtime, then you don't have a problem! You can use the battery however is convenient, and it'll be many many years before it's lost enough capacity that it can't deliver 4 hours any more. You are receiving no benefit from some complex scheme. Someone who wants to use the player for 12+ hours at a time might benefit from the battery having a longer life, but *can't achieve that* by having the charging behaviour change, because if they don't charge it as fully, or discharge it as fully, they can't get their desired runtime even while it's new.

The idea that you should have a battery that's 3-4 times the capacity you actually need is insane. Some devices happen to work out this way because their physical size/weight vs their power consumption allows for it, but most consumer electronics this is basically impossible: nobody makes a high end smartphone that lasts for most of a week on a single charge with regular usage, because you *can't do it* without making the device massive and heavy beyond what people will consider buying.

And, again, if you *have* got a battery that's 3-4 times the capacity you actually need, then caring very much about the charging behaviour is a waste of your time because it will have way more capacity than you need for a *very* long time whatever you do: it takes an extremely large number of cycles to lose 75% of capacity no matter how deep those cycles.

Quote
An extra point is that of parasitic loads, charging a device while its still on tends to trick the guage into taking more charge. Now switching off the device isn't an option while charging it, so accepting a lower charge is safer than 100%
So, here's the next problem: our devices don't have "gauges". The batteries in almost all cheap consumer electronic devices do not have smart charging controllers built in, or even state-of-charge monitoring. The charge controller is part of the device, not the battery; it rarely stores any data whatsoever, and usually it's so dumb that you actually have to drive it in realtime in software to make it charge at all, which is why a lot of these devices can't charge without switching on. The percentage of battery displayed in Rockbox is not the reading from some gauge, it's just a guess based on the current cell voltage read by an ADC, compared to a hypothetical discharge curve that's hardcoded into Rockbox for that player. It completely ignores internal resistance because we haven't got a good way to model it. That same cell voltage is also used to decide how to charge the battery (which phase of charging to be in, etc).

Smart batteries with real state of charge gauges are generally only found in laptops. So, yeah, all your comments about gauges and calibration and so on are completely irrelevant, because those things *do not exist* on any of the hardware we're talking about.

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A person that charged to 100% and used it with full DoD has got more run time out of the player, whereas i've deferred my use of it. But if they need more run time their battery isn't going to be up to it, mine will.
No it won't, because you only charged it to 70% and my regular abused battery has more than 70% of its capacity left :)

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How do you know the battery actually has this much life on it. Do you run battery benchmarks on it regularly ?
Yes, I work on charging and power management code in Rockbox, so I battery bench my devices very frequently.

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There is another point here, your's is an anecdotal experience versus testing data by a battery company. I'm more inclinced to give the latter the benefit of the doubt.
Yes, it's an anecdote. The point was it's an example of real-world capacity loss. "Testing data by a battery company" here actually means "some graphs put up by some company that makes expensive advanced battery chargers", which if you think about it is someone with a vested interest in making you think that battery charging is complicated.. :p

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An ipod has got better battery life to start with than a clip+ which maxes out at 15 hours and i've got very attached to it & RB.
Actually, the ipod video's stock battery life as quoted by Apple is 20 hours, so mine after six years lasts *longer*, thanks to Rockbox being considerably more power efficient :p

Quote
The BU docs say its good to do a calibration every 40 partial charges, if you use it everyday thats once a month. I prefer to do it once very 3 months. Not too bothered if the guage goes out of sync by even 10% in that time so long as i know the battery is still going strong.
As I mentioned above, since there are no battery gauges in these devices, this is a waste of time and is just using your battery more for no reason. The Rockbox percentage is a completely fixed calculation and the only way to get it back "in sync" is to battery-bench your device with its battery in its current state, work out approximately what the discharge curve is as a result, and modify the source code with your readings.



Edit: Also, yaknow, I'm not stopping you (or anyone else) from implementing this and trying it, though obviously testing it objectively is going to be rather time-consuming and require comparing two devices. All I've tried to do is warn people that it may not be worth the effort. If you do implement it, test it, and can show that I'm wrong and the effect is significant, then that's great and I'll help you get your patch landed as soon as possible.
Title: Re: Battery management while charging
Post by: blr_p on October 24, 2012, 05:19:36 PM
Quote
Actually, the ipod video's stock battery life as quoted by Apple is 20 hours, so mine after six years lasts *longer*, thanks to Rockbox being considerably more power efficient :p
You and another used your ipod video for 6 years and you still get 20 hours runtime out of it today (!)

You and another took no care, that means you charged to 100%, ran it till it was dead and recharged again to 100%, you've been doing this regularly for the last 6 years too.

How is that possible ? i'd have thought you'd be getting half the stated life out of it by now if not less. ok, it looks like you got a 10% drop, over the last three years but thats nothing.

Was looking at the specs of a lipo battery on allbattery.com, and the tests done on it, the vendor says 300 cycles full charge/discharge before the battery reaches 80% capacity. This is a vendor that is selling batteries, it concurs with the second graph posted above.

Lets assume its linear.

300 cycles - 80%
600 cycles - 60%
900 cycles - 40%
1200 cycles - 20%
~1400 = dead!

That's in about four-ish years time. Whereas your ipod video hasn't gone below 80% in 6 years that too with no paritcular care. I will assume you use it regularly, say a few times a week, rather than per month.

I'm sure you're aware of that lipo has no memory effect but this using it till its dead kinda makes me think of NiCads. You're doing the same with LiPo because you want the runtime.

Quote
Then maybe you need to go read more about battery chemistry rather than just relying on a single source? It is a fundamental fact of every battery technology that we have that they degrade with use no matter what you do with them. There is no free lunch. Usage pattern can change the rate of degradation, but nothing is going to stop it.
I'm aware of battery chemistry and that there is a fixed life in all batteries.

So if i buy a clip, charge it and stick in the drawer and never use it. Let's assume i have some way of ensuring the lipo battery never gets below 2.2V .  It's left there as is and never used. After some years the battery will lose capacity and eventually die.

The point where i came in is you assert that regular partial charges are worse than letting the device run down. I can't find any evidence that charging is bad, only that DoD is.

It would seem you are using your experience with the ipod video to make the statement that fewer charges, is better than more ?

Actually you cannot make that statement rather what you are saying is that nothing bad happened and here is my ipod video to show for it.

will reply to your other points later and thx for taking the time.
Title: Re: Battery management while charging
Post by: torne on October 24, 2012, 06:03:47 PM
You and another used your ipod video for 6 years and you still get 20 hours runtime out of it today (!)
Yup. It's not really a fair comparison because Rockbox really does consume significantly less power than the original firmware at this point, so if my battery was brand new I'm sure it'd get *much* more than 20 hours.

Quote
You and another took no care, that means you charged to 100%, ran it till it was dead and recharged again to 100%, you've been doing this regularly for the last 6 years too.
Not ran it until it was dead, I charge it whenever it occurs to me to do so (i.e. whenever it's convenient). I don't need to use it for 20 hours at a time, generally, but I don't recharge it every time I use it either. And yes, I charge to 100% because I just leave it plugged in until it's done.

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How is that possible ? i'd have thought you'd be getting half the stated life out of it by now if not less. ok, it looks like you got a 10% drop, over the last three years but thats nothing.
As I said, the power consumption is lower, so the battery capacity probably has dropped quite a bit. I expect it has way less than 80% of its original capacity now, but I don't really know; I can't easily battery bench it in the Apple firmware, and I'm not motivated enough to do it the hard way, and I don't exactly know what Apple's stated life is based on, so without measurements from when the battery was newer it's hard to work anything out.

Quote
That's in about four-ish years time. Whereas your ipod video hasn't gone below 80% in 6 years that too with no paritcular care. I will assume you use it regularly, say a few times a week, rather than per month.
I haven't used it much for the last year or so, but before that I used it regularly, yeah.

Quote
The point where i came in is you assert that regular partial charges are worse than letting the device run down. I can't find any evidence that charging is bad, only that DoD is.

It would seem you are using your experience with the ipod video to make the statement that fewer charges, is better than more ?
I never said anything of the sort. I said that you are unlikely to see much practical benefit from minimising depth of discharge compared to just charging it when you feel like it. Discharging it deeper and charging it fuller is worse for the battery's long term future than doing it less, but the difference just isn't that big a deal, and the practical impact of having worse runtime in the short term seems to make it pointless. Why inconvenience yourself when it's probably going to last just fine for years anyway?
Title: Re: Battery management while charging
Post by: blr_p on October 26, 2012, 11:11:59 AM
Quote
As I said, the power consumption is lower, so the battery capacity probably has dropped quite a bit. I expect it has way less than 80% of its original capacity now, but I don't really know; I can't easily battery bench it in the Apple firmware, and I'm not motivated enough to do it the hard way, and I don't exactly know what Apple's stated life is based on, so without measurements from when the battery was newer it's hard to work anything out.
Hmm i don't see any ipod video logs (http://www.rockbox.org/wiki/IpodRuntime) posted for the battery runtime plugin.

But RB can run on the ipod video  ???

It seems the runtime plugin is not available in RB for the ipod video.

Damn, so it makes it harder now to tell how your battery deterioated over time.

I found out the battery specs (http://www.all-battery.com/datasheet/30541-0%20Datasheet.pdf) i quoted in my previous post were for a 0.2C discharge load that means the battery runs down in 5 hours. That's what the graphs are referring to above. 0.2C appears to be a standard battery test.

So to interpret those graphs one must consider how long the unit takes to run down first. If its 10 hours thats a 0.1C load, if longer then even less, 15 hours is a 0.067C load.

The only way i know to get anywhere close to a 0.2C load is to play FLACS in a loop on the clip+. Otherwise with mp3s it will be longer so the load is more like 0.1C or even lower.

Am assuming a 0.1C or lower load will take longer (twice as long?)to kill the battery than a 0.2C load as its more gentle.
Title: Re: Battery management while charging
Post by: blr_p on October 27, 2012, 06:51:15 PM
This just doesn't make any logical sense. If 4 hours a session is good enough for you and the full capacity of the battery is 15 hours of runtime, then you don't have a problem! You can use the battery however is convenient, and it'll be many many years before it's lost enough capacity that it can't deliver 4 hours any more. You are receiving no benefit from some complex scheme. Someone who wants to use the player for 12+ hours at a time might benefit from the battery having a longer life, but *can't achieve that* by having the charging behaviour change, because if they don't charge it as fully, or discharge it as fully, they can't get their desired runtime even while it's new.
This is a good point. I was fearing that the clip+ would be dead in about two years with normal use so was looking to see what could be done.

There is a fixed time before a battery gives up the ghost. You can use that time either in small chunks or use more in a go. I guess this is your point, that either way you end up with nearly the same amount of work. So i guess the deep DoD isn't going to make a tangible difference. Shorter DoDs are better though its not so mandatory.

So i guess an operating range from a charge level of 20 - 90% should be ok, not full DoD nor 100% charged, that's over 10 hours run time for a battery that can deliver 15h or 70% run time.

The idea that you should have a battery that's 3-4 times the capacity you actually need is insane. Some devices happen to work out this way because their physical size/weight vs their power consumption allows for it, but most consumer electronics this is basically impossible: nobody makes a high end smartphone that lasts for most of a week on a single charge with regular usage, because you *can't do it* without making the device massive and heavy beyond what people will consider buying.
The idea comes from sizing lead acid batteries for a home UPS. Sizing is cost effective in this case as those batteries do not like deep discharges and  cycle time can be considerably reduced.

A smartphone is two levels more complicated than a clip+. First there is the transmitter/receiver that needs to increase power as and when the signal weakens and ontop of that you might be doing some cpu intensive computing on it. A lot of unpredictable and heavy pulsed loads in concert. Not charging to 100% might help.

People aren't going to give up their smartphones, better battery tech is required here.

And, again, if you *have* got a battery that's 3-4 times the capacity you actually need, then caring very much about the charging behaviour is a waste of your time because it will have way more capacity than you need for a *very* long time whatever you do: it takes an extremely large number of cycles to lose 75% of capacity no matter how deep those cycles.
ok, so i still have the point about not charging to 100%. Here is another article (http://lancair.net/lists/lml/Message/56976-02-B/Li-Ion%20Battery%20Life.pdf) in favour.

(http://img213.imageshack.us/img213/4508/graph2l.png)

Quote from: PCT
Always maintaining a Li-ion battery in a fully charged condition will shorten its lifetime. The chemical changes that shorten the battery lifetime begin when it is manufactured, and these changes are accelerated by high float voltage and high temperature. Permanent capacity loss is unavoidable, but it can be held to a minimum by observing good battery practices when charging, discharging or simply storing the battery. Using partial-discharge cycles can greatly increase cycle life, and charging to less than 100% capacity can increase battery life even further

(http://img203.imageshack.us/img203/1875/graph1z.png)

Quote from: PCT
A 100-mV to 300-mV drop in float voltage can increase cycle life from two to five times or more. Li-ion cobalt chemistries are more sensitive to a higher float voltage than other chemistries.
That means choose whether to charge to 90% or as low as 70%.

So, here's the next problem: our devices don't have "gauges". The batteries in almost all cheap consumer electronic devices do not have smart charging controllers built in, or even state-of-charge monitoring. The charge controller is part of the device, not the battery; it rarely stores any data whatsoever, and usually it's so dumb that you actually have to drive it in realtime in software to make it charge at all, which is why a lot of these devices can't charge without switching on. The percentage of battery displayed in Rockbox is not the reading from some gauge, it's just a guess based on the current cell voltage read by an ADC, compared to a hypothetical discharge curve that's hardcoded into Rockbox for that player. It completely ignores internal resistance because we haven't got a good way to model it. That same cell voltage is also used to decide how to charge the battery (which phase of charging to be in, etc).

Smart batteries with real state of charge gauges are generally only found in laptops. So, yeah, all your comments about gauges and calibration and so on are completely irrelevant, because those things *do not exist* on any of the hardware we're talking about.
Interesting, did not realise there was so much control of charging in user land, thought the devices firmware would be responsible and the only option available to RB would be charge to 100% or nothing.

This means you have to individually code a charging algorithm for each device RB is ported too, that is if you allow RB to do charging on that device  in the first place.

Incidentally what criteria do you use to decide the battery is full and to stop the charging ? That the 4.2V is reached along with timing ?

If its hit and miss then not charging to 100% would be preferable.

Thing is the battery benches tend to be close to what the user expects assuming the battery is in good working order, not read any comments that the RB 'gauge' is wildly off so far.

Yes, it's an anecdote. The point was it's an example of real-world capacity loss. "Testing data by a battery company" here actually means "some graphs put up by some company that makes expensive advanced battery chargers", which if you think about it is someone with a vested interest in making you think that battery charging is complicated.. :p
Ah yes what a conspiracy  :D

Quote from: BU
Chargers for cellular phones, laptops, tablets and digital cameras bring the Li-ion battery to 4.20V/cell. This allows maximum capacity, because the consumer wants nothing less than optimal runtime. Industry, on the other hand, is more concerned about longevity and may choose lower voltage thresholds. Satellites and electric vehicles are examples where longevity is more important than capacity.
Cadex caters to industry, not the consumer.

The CPF forums where the LED torch geeks hang out are crazy about analysers. Theirs is an even simple task than with PMP's with a nice DC load

I've got a MAHA for AA/AAA batteries and its been very helpful with knowing which batteries to use, pair with and maintain.

Not going to 100% is the only point that really matters with a PMP  and i don't think that's very complicated in comparison.


As I mentioned above, since there are no battery gauges in these devices, this is a waste of time and is just using your battery more for no reason. The Rockbox percentage is a completely fixed calculation and the only way to get it back "in sync" is to battery-bench your device with its battery in its current state, work out approximately what the discharge curve is as a result, and modify the source code with your readings.
Ah ok. So if i run battery benches every 3 months then that is what i have to do.

Edit: Also, yaknow, I'm not stopping you (or anyone else) from implementing this and trying it, though obviously testing it objectively is going to be rather time-consuming and require comparing two devices. All I've tried to do is warn people that it may not be worth the effort. If you do implement it, test it, and can show that I'm wrong and the effect is significant, then that's great and I'll help you get your patch landed as soon as possible.
Comparing with another device is not possible, though ideal.

Can i prove to everybody here that this is a better strategy for longer battery life ? no, all i can do is point to the sources, reputable ones that say not charging to 100% is better. So i will do that for now.

There is an IEEE paper from 2006 that talks about the same thing but i've not been able to get a copy.

Getting it to the right amount so far turns out to be a matter of timing, its ~a half hour from 40-80% or a little more. Using a longer range needs to adjust accordingly.

If this idea ever makes it into the RB build, and the mistaken notion is created that RB has less runtime, because the charge level stops at a certain point, will that create a misconceptoin, that poor saratoga will have to spend a year explaining ;D
Title: Re: Battery management while charging
Post by: saratoga on October 28, 2012, 05:19:18 PM
Quote
As I said, the power consumption is lower, so the battery capacity probably has dropped quite a bit. I expect it has way less than 80% of its original capacity now, but I don't really know; I can't easily battery bench it in the Apple firmware, and I'm not motivated enough to do it the hard way, and I don't exactly know what Apple's stated life is based on, so without measurements from when the battery was newer it's hard to work anything out.
Hmm i don't see any ipod video logs (http://www.rockbox.org/wiki/IpodRuntime) posted for the battery runtime plugin.

But RB can run on the ipod video  ???

FYI, the Ipod Video is also called the "Ipod 5G". 

It seems the runtime plugin is not available in RB for the ipod video.

Sure it is.

The only way i know to get anywhere close to a 0.2C load is to play FLACS in a loop on the clip+.

FLACs on the Clip+ last almost 20 hours with a new battery, so you're closer to .05C.  You'll never get up to 0.2C on an MP3 player, they use far too little power to discharge that quickly.

A smartphone is two levels more complicated than a clip+. First there is the transmitter/receiver that needs to increase power as and when the signal weakens and ontop of that you might be doing some cpu intensive computing on it. A lot of unpredictable and heavy pulsed loads in concert. Not charging to 100% might help.

Thats no different then an mp3 player.
Title: Re: Battery management while charging
Post by: torne on October 29, 2012, 05:12:11 AM
Quote
As I said, the power consumption is lower, so the battery capacity probably has dropped quite a bit. I expect it has way less than 80% of its original capacity now, but I don't really know; I can't easily battery bench it in the Apple firmware, and I'm not motivated enough to do it the hard way, and I don't exactly know what Apple's stated life is based on, so without measurements from when the battery was newer it's hard to work anything out.

But RB can run on the ipod video  ???

It seems the runtime plugin is not available in RB for the ipod video.

Damn, so it makes it harder now to tell how your battery deterioated over time.

You have misinterpreted what I said again. The battery bench plugin works fine on ipodvideo, as you should've been able to figure out from me saying I battery bench it often :) But you can't run the battery benchmark *in the Apple firmware*, because obviously Rockbox isn't running, so the only way to measure battery life in the Apple firmware is to actually time it manually while listening to the device so you know when it cuts out, and I can't really be bothered (plus I don't use iTunes, so I don't have any music on the player in a form that the Apple firmware can read). This means I can't compare the battery runtime it gets now to the *quoted* runtime from the device's specs, because comparing Apple's quoted runtime to Rockbox's current runtime is not a fair comparison: Rockbox is significantly more power efficient on this device, and so it will always get more runtime than Apple's firmware for *any* given state of the battery. The device was used for years by a friend before I came into possession of it, and they never used Rockbox, so I don't have any battery bench results for it that aren't from when I got it halfway through its life.

Quote
I found out the battery specs (http://www.all-battery.com/datasheet/30541-0%20Datasheet.pdf) i quoted in my previous post were for a 0.2C discharge load that means the battery runs down in 5 hours. That's what the graphs are referring to above. 0.2C appears to be a standard battery test.

So to interpret those graphs one must consider how long the unit takes to run down first. If its 10 hours thats a 0.1C load, if longer then even less, 15 hours is a 0.067C load.

The only way i know to get anywhere close to a 0.2C load is to play FLACS in a loop on the clip+. Otherwise with mp3s it will be longer so the load is more like 0.1C or even lower.

Am assuming a 0.1C or lower load will take longer (twice as long?)to kill the battery than a 0.2C load as its more gentle.

As saratoga pointed out we don't come anywhere near 0.2C load. FLAC is actually a pretty efficient codec, also; we have a number of codecs that need way more power than that. :)
Title: Re: Battery management while charging
Post by: torne on October 29, 2012, 05:36:48 AM
This is a good point. I was fearing that the clip+ would be dead in about two years with normal use so was looking to see what could be done.

There is a fixed time before a battery gives up the ghost. You can use that time either in small chunks or use more in a go. I guess this is your point, that either way you end up with nearly the same amount of work. So i guess the deep DoD isn't going to make a tangible difference. Shorter DoDs are better though its not so mandatory.
Yes, this is exactly my point. Your clip+ will, in all likelihood, still have perfectly good battery runtime after 5+ years of normal use. It probably will have a little more runtime after 5+ years of careful use with 20-90% charge cycles, but going out of your way to make sure you do this seems pointless to me because the benefit is really not that great.

Quote
The idea comes from sizing lead acid batteries for a home UPS. Sizing is cost effective in this case as those batteries do not like deep discharges and  cycle time can be considerably reduced.
Lead acid UPS batteries don't have to fit in your pocket, or be light enough to carry, so yes, of course in that environment you can buy as big a battery as you feel like, and getting one that's several times the capacity you think you will need is perfectly reasonable. This is a meaningless comparison to bring up in this context :)

Quote
A smartphone is two levels more complicated than a clip+. First there is the transmitter/receiver that needs to increase power as and when the signal weakens and ontop of that you might be doing some cpu intensive computing on it. A lot of unpredictable and heavy pulsed loads in concert. Not charging to 100% might help.
This is exactly the kind of load you have on our devices as well, though. The CPU usage varies depending on what codec you are playing right now, and varies frequently during playback as well as the clock gets scaled up and down depending on the PCM buffer fullness, and powering the flash memory/disk/screen are the occasional high-current draws that come at not-entirely-predictable times that are much like radio transmissions :)

Quote
ok, so i still have the point about not charging to 100%. Here is another article (http://lancair.net/lists/lml/Message/56976-02-B/Li-Ion%20Battery%20Life.pdf) in favour.
As I've pointed out *numerous* times now, I understand perfectly fine how charging to the highest possible state of charge is bad for the battery and I've not said a single thing that contradicts this. I'm just going to ignore you continuing to repeat the same points.

Quote
Interesting, did not realise there was so much control of charging in user land, thought the devices firmware would be responsible and the only option available to RB would be charge to 100% or nothing.
Rockbox *is* the device's firmware (except on Android devices and the yp-r0, where it runs as a linux app). There is no "user land"; all of Rockbox runs in kernel mode and there is no other software running on the device once Rockbox boots. Some devices have a hardware charge controller that handles the entire logic of charging (like the ipodvideo, in fact, which has a LTC4066), but other than those devices, we *have* to drive it manually. Even when there is a hardware charge controller, we generally still have the ability to tell it to stop charging (the code for this is present but not used on ipodvideo) since it normally has an input for that, though it would have to be based on our ADC reading for the battery voltage since the controller doesn't usually tell you anything about state-of-charge.

Quote
This means you have to individually code a charging algorithm for each device RB is ported too, that is if you allow RB to do charging on that device  in the first place.
Yes, on devices where charging is not handled entirely in hardware we have to write the whole thing.

Quote
Incidentally what criteria do you use to decide the battery is full and to stop the charging ? That the 4.2V is reached along with timing ?
Different on different devices. We do what the datasheet says, or what the original firmware does, or what seemed to be a good idea after experimenting with it. I didn't write any of this code, so I don't know :)

Quote
Thing is the battery benches tend to be close to what the user expects assuming the battery is in good working order, not read any comments that the RB 'gauge' is wildly off so far.
People complain about the battery percentage being grossly inconsistent quite often, and it's usually because they have an old battery that's built up a high internal resistance. But, they are usually complaining about devices that are well over five years old; devices like the Clip weren't released long enough ago to have experienced significant battery degradation yet to the point where users will actually notice the percentage being a bad indicator.

Quote
Ah yes what a conspiracy  :D
That wasn't really a serious comment; just trying to remind you that there are multiple sources out there with different experiences :)

Quote
Comparing with another device is not possible, though ideal.
Sure it is, source two batteries from the same batch and install them in two identical players. I implied it was impractical, and it is, but it's quite possible. :)

Quote
Can i prove to everybody here that this is a better strategy for longer battery life ? no, all i can do is point to the sources, reputable ones that say not charging to 100% is better. So i will do that for now.
Everybody here who knows anything about batteries already knows this is a better strategy for longer battery life. I know it. That's not what I'm asking you to demonstrate. I'm asking you to demonstrate that the practical impact on a normal user using their mp3 player in a normal way, with or without this charging change behaviour in Rockbox, is actually something that the user will notice as an improvement.

My experience messing with devices, the sources I've read (including your sources, which do not disagree with my knowledge/experience at all), and the anecdotes of people using Rockbox on devices that have used the same battery for many years, suggest that the effect is not big enough to be worth the trouble, for these devices. This does not mean that it's not actually an objectively better strategy, or that it doesn't have much bigger benefits on other devices with different battery management behaviours or different load profiles, or that we'd reject a patch that implemented this strategy as an option (in a clean and well-designed way). It just means that I'm not going to implement it for you, and that I'm not going to try and convince anyone else to implement it for you either :)
Title: Re: Battery management while charging
Post by: bertrik on October 29, 2012, 06:09:31 AM
Ok, so I think everyone agrees that charging to less than 100% can be beneficial for battery life (number of cycles), but there is disagreement on the extent this actually makes a difference in practical use. If we were to add a feature to allow the user to make a choice, I wonder what we can offer.

As a practical implementation, there are several things we can influence w.r.t. charging, depending on the target:
* voltage levels for warning and power-off
* current for the constant current part of the charge (40% of the battery capacity for example)
* voltage for the constant voltage part of the charge (4.20V for example)
* cut-off current for the constant voltage part of the charge (10% of the CC-current for example)

IMO, users can keep an eye on discharge levels themselves, so we don't have to manage that in software.
In rockbox, what we could do is to offer options for the constant voltage part, again depending on target, like from 4.00V to 4.20V.
(*if* we do this, I'd like to keep things simple, and offer only 1 parameter to configure).

If we are to allow lower voltages, I guess there will also be users who want a higher voltages. I think we should forbid that though.


Title: Re: Battery management while charging
Post by: AlexP on October 29, 2012, 02:30:53 PM
I really really wouldn't want an option for this.  We have far too many already without adding such an esoteric one.  If there really is an advantage (which there doesn't seem to be in practical terms) then it should just be changed.
Title: Re: Battery management while charging
Post by: blr_p on October 29, 2012, 02:59:55 PM
FLACs on the Clip+ last almost 20 hours with a new battery, so you're closer to .05C.  You'll never get up to 0.2C on an MP3 player, they use far too little power to discharge that quickly.
yeah, i noticed getting up to 16 -17h (even with q8 compresion) in the some people's logs for the clip+ with FLACs. I was thrown by a thread i'd seen in ABI where the user was complaining of less than 7 hours run time with FLACs and it was in OF. He replaced the player and tried with RB but still got the same out of it. That thread did not really reach much of a conclusion.

I can't see any way to get close to a 0.2c load on the clip+, playing FLACS & doom at the same time ? heh, not exactly a normal scenario. It would take something unusal or a decode heavier than FLAC. To put it simply if a user is getting 5 hours doing whatever then they've got a 0.2c load. Its then that the vendors graphs apply ~400 cycles to 80% capacity.

So the question then is, does a lower load mean a longer number of cycles than a 0.2c load. I cannot find any data on that. Looking at some docs they talk about 2c, 1c, 0.2c and you can see the lower the load the more the cycles before the battery comes down to 80%. So presumably lower loads result in more cycles before 80%

But how many more is unclear to me.

Post Merge: October 29, 2012, 03:21:05 PM
I guess if you find more data, you could try and make a better argument. 
More research papers would help build the case, is there anyone here with an IEEE subscription ?

This paper looks interesting.

How Depth of Discharge Affects the Cycle Life of Lithium-Metal-Polymer Batteries
This paper appears in:
Telecommunications Energy Conference, 2006. INTELEC '06. 28th Annual International
Date of Conference: Sept. 2006
Author(s): T. Guena
P. Leblanc
Page(s): 1   - 8
Product Type: Conference Publications
Conference Location :  Providence, RI
E-ISBN :  1-4244-0431-2
Print ISBN: 1-4244-0430-4
INSPEC Accession Number: 9296660
Digital Object Identifier :  10.1109/INTLEC.2006.251641
Date of Current Version :   04 December 2006
Issue Date :   Sept. 2006



Post Merge: October 29, 2012, 03:27:53 PM
You have misinterpreted what I said again. The battery bench plugin works fine on ipodvideo, as you should've been able to figure out from me saying I battery bench it often :) But you can't run the battery benchmark *in the Apple firmware*, because obviously Rockbox isn't running, so the only way to measure battery life in the Apple firmware is to actually time it manually while listening to the device so you know when it cuts out, and I can't really be bothered (plus I don't use iTunes, so I don't have any music on the player in a form that the Apple firmware can read). This means I can't compare the battery runtime it gets now to the *quoted* runtime from the device's specs, because comparing Apple's quoted runtime to Rockbox's current runtime is not a fair comparison: Rockbox is significantly more power efficient on this device, and so it will always get more runtime than Apple's firmware for *any* given state of the battery. The device was used for years by a friend before I came into possession of it, and they never used Rockbox, so I don't have any battery bench results for it that aren't from when I got it halfway through its life.
ok, now its more clear. I was confused why you mentioned benchmarking in apple when you already had RB's run time plugin. Forget about apple and what they claim run time should be.

Now the question is, how did you find the battery life evolve over the years in RB with the logs you got.
Title: Re: Battery management while charging
Post by: torne on October 30, 2012, 06:02:42 AM
ok, now its more clear. I was confused why you mentioned benchmarking in apple when you already had RB's run time plugin. Forget about apple and what they claim run time should be.

Now the question is, how did you find the battery life evolve over the years in RB with the logs you got.
I already gave you some estimates of this earlier in the thread.

When I got it originally, the battery life in Rockbox was substantially *worse* than it is now, as that predates some significant power management improvements on ipodvideo. After most of the improvements were in about 2.5 years ago, I got about 22 hours of runtime. Currently I get about 20.5. There haven't been *major* power management changes in that time, but obviously the code is different.
Title: Re: Battery management while charging
Post by: soap on October 30, 2012, 08:22:50 AM
Just wanted to chime in that I've been abusing my iPod 5th gen battery since 8 hours runtime was the norm.  I have many (older) battery benches posted, both in Rockbox and with Apple firmware.  I've run my battery down to (uncalibrated!) zero scores of times and still get > 18H on MP3.
Title: Re: Battery management while charging
Post by: [Saint] on October 31, 2012, 02:25:37 AM
I might as well add my story too:

I have an iPod 4G (Color/Photo) with the original battery in that I treat like absolute dirt by the standards outlines in previous posts. I charge it whenever the hell I feel like it, run it down to zero with absolutely no regard, and regularly leave it on the charger for days on end.
I am at least the second owner of this device so the person(s) before me may very well have treated it worse than I do...let me reiterate that this is the same battery the device was produced with, and (unlike my other iPod Color/Photo) still has the original HDD in place. I can get ~18+ hours out of it with mp3 @320.
Title: Re: Battery management while charging
Post by: blr_p on November 04, 2012, 05:56:39 PM
I am at least the second owner of this device so the person(s) before me may very well have treated it worse than I do...let me reiterate that this is the same battery the device was produced with, and (unlike my other iPod Color/Photo) still has the original HDD in place. I can get ~18+ hours out of it with mp3 @320.
How old's the unit ?
Title: Re: Battery management while charging
Post by: torne on November 04, 2012, 06:50:53 PM
They stopped making the ipod photo in mid-2005, so at least seven years :)