Document with answers to most popular battery-related questions is ready

Rafael Campos methril at
Mon Aug 3 10:05:58 CEST 2009

Nice discussion on the follow mails, but i've a doubt

On Sun, Aug 2, 2009 at 7:07 PM, Paul Fertser <fercerpav at> wrote:

> Hi,
> This is a text version of the wikipage [1], feel free to ask new questions
> there on the talk page. Discussion on this ML is also appreciated (and
> in fact i'm more comfortable with ML than the wiki).
> Openmoko devices
> Battery questions and answers
> NB: Some of the described behaviour depends on the kernel, the
> relevant code was pushed on 02 Aug to andy-tracking
> Hardware capabilities
> Q: What batteries can be used with gta01 and gta02?
> A: Original OM gta01, gta02, Nokia BL-5C, BL-6C and compatibles.
> Q: Do other BL-5/6C compatible batteries fit?
> A: If the battery is thicker than BL-6C, you won't be able to close
> the back cover.
> Q: What is the difference between all those types?
> A:
> Capacity:
> gta01, gta02            - 1200 mAh
> BL-5C old (newer/new)   - 850 (970/1050) mAh
> BL-6C                   - 1150 mAh
> Temperature control:
> gta01, BL-5C, BL-6C     - thermistor
> gta02                   - bq27000
> Special features:
> gta02 - accurate and sophisticated reporting of capacity,
> time_to_full, time_to_empty, temperature and battery current during
> both charge and discharge thanks to bq27000 (aka Coloumb Counter)
> Q: What are hardware capabilities of gta01 and gta02 with regard to
> battery management?
> A:
> gta01: charging all battery types, measuring temperature with
> battery-integrated thermistor (currently charging and measuring
> temperature for non-gta01 batteries doesn't work due to the kernel
> driver issues but it's software limitation), measuring battery output
> voltage, very inaccurate and noisy measuring of battery current
> gta02: charging all battery types, measuring battery output voltage,
> communicating with bq27000
> Q: Can nokia phones use/charge gta01/gta02 batteries?
> A: gta01 and gta02 batteries will fit wherever BL-6C fits but they
> can't be charged in nokia phones unless you isolate the middle pin
> from the battery and connect a resistor of ~50k (actual measured value
> on a cold (25C) battery is 75k, on a slightly warm battery - 82k) from
> it to the ground (to fake a thermistor presence).
> Q: Can third-party chargers charge gta01/gta02 batteries?
> A: The "good" ones will most probably require the same trick needed
> for nokia phones. More cheaper ones are more likely to ignore
> thermistor absence.
> Q: I have several compatible batteries. What are the storage
> requirements for them?
> A: Keep in a dry cool place charged to no more than 75%.
> Safety issues
> Q: Do OM devices control temperature to stop charging if the battery
> gets too hot?
> A: No (probably gta01 does, need to check).
> Q: Isn't it dangerous?
> A: No, since all batteries (not raw cells!) have an integrated
> protection circuits.
> Q: Can i use that fancy 2800 mAh BL-5C-compatible battery i saw on
> ebay?
> A: Unless you want an explosion in your pocket i wouldn't recommend
> using any battery that is not produced by a reputable vendor and
> widely tested. And even reputable vendors make mistakes, nokia once
> had to recall 46 million batteries manufactured by Matsushita (
> ).
> Q: You say that BL-5C is compatible with my gta02. Does that mean i
> can use that BL-5C-compatible bat i bought for a buck from a bum?
> A: You bet, go ahead.
> Charging
> Q: My battery charges to 100% but then charging stops and the battery
> keeps discharging, wtf?
> A: LiIon batteries don't like to be kept fully charged, so the charger
> stops as soon as charging current becomes less than threshold. If you
> have GSM on it will discharge the battery.
> Q: But why doesn't it ever stop charging on my device?
> A: The GSM modem is connected directly to the battery terminals so if
> it's active, charger will think it's still charging the battery and
> won't turn off unless GSM becomes inactive. The default threshold is
> about 16mA, the latest Qi increases the threshold to ~32mA.

Is this true for gta02 deevices only or it's the same for gta01?

> Q: Does it mean if i leave my phone plugged it will eventually fully
> discharge the battery?
> A: On gta02 the charger will restart the charge automatically once the
> battery voltage reaches ~4V which corresponds to ~76%. Not sure about
> gta01, requires more investigation. :-/
> Q: Ok, how to make sure my battery is fully charged before a long
> trip?
> A: Replug the charger, it will trigger charging no matter what the
> current capacity is.
> Q: My power/aux LED indicates charging/discharging/whatever, what does
> that mean (aka why it's still blue even after i unplugged the
> charger)?
> A: Ask FSO guys about it, some of them think that the user shouldn't
> really know what's happening and therefore they do some special
> mangling of "status" sysfs node before presenting it to the user. If
> you want to make a decent bugreport please add clear steps to
> reproduce and /sys/class/power_supply/battery/uevent contents for all
> relevant states.
> Using compatible batteries with gta02
> Q: So, how do i use "dumb" batteries with my freerunner?
> A:
> First you need to unbind bq27000 driver:
> echo bq27000-battery.0 > /sys/bus/platform/drivers/bq27000-battery/unbind
> Then you load the dumb battery driver:
> modprobe gta01_battery
> If you need to use bq27000 driver again, do:
> rmmod gta01_battery
> echo bq27000-battery.0 > /sys/bus/platform/drivers/bq27000-battery/bind
> If you use Enlightment you might need to restart it after that.
> Q: Is capacity reported for dumb batteries accurate?
> A: During discharge it should be pretty (+-10%) accurate, during
> charge the capacity reported is ~20% more than real.
> Q: Why does /sys/class/power_supply/battery/charge_full says i have a
> 850 mAh battery no matter what i use?
> A: It's a workaround to make popular battery gadgets work with this
> driver.
> This Q&A were prepared by
> Paul Fertser <fercerpav at>
> Joerg Reisenweber <joerg at>
> [1]
> --
> Be free, use free ( software!
> mailto:fercerpav at
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Rafael Campos
o0 Methril 0o
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