XXL battery ?

Michael Shiloh michael at openmoko.org
Thu Apr 17 23:59:56 CEST 2008

Not exactly "pocketable", but large batteries with built-in USB power 
outlets, like certain universal laptop batteries, seem a handy way to do 


Werner Almesberger wrote:
> We had a little discussion about doing intensive data logging,
> e.g., to combine location data from GPS, WLAN, and GSM.
> For just getting an as comprehensive as possible dump, on which
> one can then do data mining, a much larger capacity battery would
> be very useful to have.
> If we hook a series of bare D cells (to pick the largest easily
> available and still pocketable battery type) to the Neo's battery
> terminals, we're limited by the PCF50633's maximum battery voltage
> of 5.5V (6.5V for the GTA01's PCF50606) and the threshold when our
> LDOs lose regulation, which is around 3.6V, a bit less without
> microSD.
> With alkaline D cells [1], 20500mAh with a maximum voltage of
> 1.5V/cell, that would be three cells in GTA02. If we assume that we
> draw 200mA (GPS, WLAN, and GSM powered up and passively listening,
> backlight off), we'd reach the 1.2V cut-off after about 30 hours.
> So that's one set of batteries every 3-4 days, or 900g of extra
> trash that's still 66% "full" per week.
> With rechargeable NiCad D cells [2], 4400mAh nominal and a maximum
> voltage of about 1.35V/cell, we could use four cells. That would put
> the cut-off voltage at 0.9V, at which the battery is considered to
> be empty anyway. That would give us about 22 hours, until it's back
> to the charger. Not too bad, and evironmentally less objectionable
> in the long run.
> NiMH [3] disappoint a bit with only 2500mAh per cell, which would
> give us something like 12.5h.
> [1] http://rocky.digikey.com/weblib/Energizer/Web%20Data/EN95.pdf
> [2] http://sanyo.wslogic.com/pdf/pdfs/KR-4400D.pdf
> [3] http://data.energizer.com/PDFs/NH50-2500.pdf
> So far the theory. I wonder if anyone has actually tried such a
> setup, and what the experiences are.
> - Werner

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