Battery life [was: Re: Can the Freerunner now be charged with 1 or with 2 Amp ?]

[Andy Green]

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Somebody in the thread at some point said:
| Am Di  24. Juni 2008 schrieb Yorick Moko:
|> It is known that the way you charge a battery influences the lifetime.
|> Have there been any tests as to which is the "best" way to charge the
|> freerunner?
|
| Nope, didn't find the time to do the expected >500 charge/discharge
cycles ;-)
| Honestly, this is nothing FR or OM specific. Considerations valid for all
| LiIon batteries apply here as well.
| AFAIK, it's much more important not to push the last electron into the
battery
| that might fit in here, than to charge with lower current. Some notebooks
| allegedly have a "treat battery nice" option, that stops charging at
| ~75%..90%. You could do this by adjusting the Vbat-max setting of PMU.
Til
| now, nobody cared about it yet.

Actually with the charging LED patches in I have been able to see when
we charge for a while now, it seems it does an OK job with current
settings of recognizing a full or nearly full battery and not needlessly
charging it.

It does continue to charge the battery past the point that the coulomb
counter in the battery reports 100% capacity reached, but it does it in
constant voltage mode where the current it pushes in varies according to
the effort needed to keep the voltage up.  In the final phase of the
charging this decreases second by second to under 100mA and then cuts
off as full.

I had a read through this which seems to be written by an experienced
Li-ion person:

http://www.batteryuniversity.com/parttwo-34.htm

First he shows a graph about charging voltage: ours is set to 4.2V right
now so we fit the best lifetime curve he shows there.

Second he shows a graph about rate of charge and discharge, I don't
really know how to map that on to our performance, except that I never
saw a battery heating under charge to more than 30 degrees C and that on
a hot day, and I don't think our discharge rate of ~200mA typ when not
transmitting will be "excessive".  Well, dealing with high currents
during transmit it what a mobile phone battery is for.

But he doesn't seem to mention charge level except to say that for
storage, you don't want a 100% charged battery but 40% charge level.  So
AFIK what we do now does not make any special trouble for battery life.

- -Andy
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