[Power] quick question.. battery

[Nicholas]

Richard, very useful thanks.

On 7/23/12, Richard A. Smith <richard at laptop.org> wrote:
> On 07/21/2012 07:26 AM, Nicholas wrote:
>
>> My question is if I was to construct a charger to provide for a
>> maximum of say 600mA at a certain regulated voltage and if there were
>> a recommended voltage for external charging what would that
>> recommended supply voltage be? That is, going straight in to the
>> terminals of the battery.
>> 6.5v?
>
> 6.5V is the nominal full charge operating voltage which is not equal to
> the charging voltage. With 6.5V you won't ever reach full charge.
>
> Standard charging procedure is contant current of .5C (ie 1.4A) until
> the battery voltage reaches 7.5V and then constant voltage until the
> charge current falls below 60mA.
>
> The XO [1] uses a slightly different procedure which is CC up to 2A
> until we reach just over 7.4V and then CV until the current falls below
> 120mA.
>
> [1] Overall. Each generation of the laptop has a slightly different
> behavior due different charging hardware.  And of course the XO's
> monitor the temperature of the battery and back off it rises above 40
> degC.  But you have to talk 1-wire to get that info.
>
> --
> Richard A. Smith  <richard at laptop.org>
> One Laptop per Child
>
>
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