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Using an AC Charger to Charge my Sansa e280

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dgreenb2:
I have no problem charging my Rockboxed Sansa e280 using a direct USB connection to my computer. I am unable, however, to charge my Sansa's battery while connected to either an AC charger, or to a 12 volt automobile converter.

The Sansa can use both the AC converter & auto charger to play mp3s. The Sansa battery won't charge, though, when I'm connected in this way.

Am I doing anything wrong?

saratoga:

--- Quote from: dgreenb2 on December 30, 2008, 04:49:27 PM ---
The Sansa can use both the AC converter & auto charger to play mp3s. The Sansa battery won't charge, though, when I'm connected in this way.


--- End quote ---

Battery charging hasn't been committed for the Sansas so you cannot charge except in the original firmware.

ldobbs:
My e280 charges off a Belkin AC or car adapter while running Rockbox, but very slowly. Starting at 10% indicated, it'll get up to about 30% after an hour or so. I'm pretty sure the Sansa interface would charge it completely in about the same time.

I'd always assumed this was because Rockbox drains the battery a lot faster than the native Sansa interface. I guess I'm lucky that it charges at all.

dreamlayers:

--- Quote from: ldobbs on January 02, 2009, 12:44:24 PM ---My e280 charges off a Belkin AC or car adapter while running Rockbox, but very slowly. Starting at 10% indicated, it'll get up to about 30% after an hour or so. I'm pretty sure the Sansa interface would charge it completely in about the same time.

I'd always assumed this was because Rockbox drains the battery a lot faster than the native Sansa interface. I guess I'm lucky that it charges at all.

--- End quote ---

I don't think Rockbox uses that much more power.   It's more probable that incoming current is limited to 100 mA.   A device must ask for permission before increasing its limit to 500 mA, so I expect hardware is configured for 100 mA.  Merely asking for and receiving permission (which Rockbox can do) would not reconfigure anything on the device.  Software needs to do something else for that.  USB chargers generally just supply power and can't talk to the device via USB, and the limit has to be set to 500 mA in such cases also.

Some people have a similar problem with iPods.  BTW In the case of iPods, a PCF ADC input can be connected to the USB data lines.  I think the OF uses that to see if it's connected to actual USB or just a charger.

saratoga:

--- Quote from: ldobbs on January 02, 2009, 12:44:24 PM ---I'd always assumed this was because Rockbox drains the battery a lot faster than the native Sansa interface. I guess I'm lucky that it charges at all.

--- End quote ---

Nope.  In fact we use quite a bit less power, hence the increased battery life in rockbox verses the retail firmware.


--- Quote ---It's more probable that incoming current is limited to 100 mA.

--- End quote ---

Even less then that.  If the charge controller isn't initialized, it seems to trickle charge at 50mA, at least for some people.  This is probably to keep a badly drained battery alive even if the sansa isn't booted up. 


--- Quote ---   A device must ask for permission before increasing its limit to 500 mA, so I expect hardware is configured for 100 mA.

--- End quote ---

Fun fact: the Sansa doesn't bother to request power, it just starts charging regardless of what its hooked up to.   It seem to take the 100mA limit as a suggestion not a requirement. 

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