Re: [avr-chat] Li-ion cell phone batteries

[Joerg Wunsch]

Robert L Cochran <address@hidden> wrote:

> The charger I mention below is specifically made
> for LiPo and Li-Ion batteries.

That's a good start.  The next thing you'd have to do is to find
enough information about the actual cell (manufacturer and
manufacturer type number) to get a datasheet.  The datasheet is the
only place where you'll find things like the maximum charge current.
For the maximum voltage, 4.20 V (usually to maintain within ±50 mV) is
a safe first guess if you don't know it exactly, only very old LiIons
have been limited to 4.10 V.

It's very likely that your black and red wires are the battery poles,
and the blue one goes to a thermistor (against black, the negative
pole) that is used to monitor the battery temperature when charging
inside the cell phone.  This is because the cell phone charger circuit
wants to charge with the highest possible current (so the charging
time gets as short as possible).  If you reduce your current to a safe
value beforehand, you are not strictly required to also monitor the
temperature.

I've been charging LiIons and LiPos with (good!) lab power supplies
many times without any troubles.  Unlike the RC car community
mentioned (who are also interested in short charge times), when
limiting the current to sane values, and being very picky about the
voltage limit, the danger will be reduced to the same level as when
charging it inside your cell phone.

> I'll look over Digikey in the morning. My problem is, I don't know
> what to call these tiny 3-wire connectors.

Sorry, I don't have an idea about that either.

> And worst of all, I'm not an electrical engineer...I'm just an
> assembly language programmer struggling to understand circuits...but
> I sure like playing with them!

If you want a faster start, get a lab power supply. ;-)

-- 
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)