Old 05-15-2013, 06:05 PM
LADave LADave is offline
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Join Date: May 2013
Location: greater Los Angeles
Posts: 4
Default Auxilliary battery

I want to replace my e250's internal battery with a higher capacity external pack consisting of at least three NiMH C cells, which should give me about 5,000 MAH and 168 hours of uptime.

I want this setup for community noise data collection where I will log decibels at 1/8 second intervals. I will also record PCM clips of high-noise incidents. I will need to create a RockBox variant for this. I will want to run this application for 24 hours up to a full week unattended.

Should I remove the existing battery? Seems like if I leave it in place, the auxilliary pack will be pushing current through trying to charge it, wasting precious capacity.

Can I even remove the existing battery and then attach the external setup through the USB/dock connection? And if I do this, will I need to use four cells instead of three to bring volts up close to the 5v USB standard?
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Old 05-15-2013, 06:43 PM
saratoga saratoga is offline
Rockbox Developer / Moderator
Join Date: Apr 2007
Posts: 3,732

You'll need to give it close to 5v if by USB. 3.2-4.3 is tolerable over the battery terminal.

Removing the lipoly battery isn't a bad idea if you use USB, but if you do, you'll need to put a resistor across the pin for the thermal sensor. The e200 will not boot unless the thermistor is reporting close to room temp. You can figure out what you need to use by sticking an ohm meter on the battery terminals. IIRC its a 10k thermistor but its been years since I played with the 200 charge circuits so I could be wrong.

I suspect that if you do use the USB port, you'll need to account for additional power losses in the USB voltage regulator. I have no idea what these are like.
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