Rockbox Development > Feature Ideas
Battery management while charging
dreamlayers:
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.
FaN:
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%!
bertrik:
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?
torne:
--- Quote from: FaN on February 24, 2012, 02:57:15 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%!
--- End quote ---
RC cars, and real cars, have drastically different load characteristics to portable consumer electronics. The effect really is a lot less than you think. :)
FaN:
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
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?
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