Building Li-ION Battery Packs

[xwingband]

BTW - how do smart chargers detect when the pack is charged?

Yes, that's what makes them "Smart".

lol, They stop charging every once and a while to check the voltage.

[virus692]

I found this cool site from ECN Magazine.
http://www.tadiranbat.com/home.php
they do custom and different batteries.

[LordArgyll]

I wonder if my charger is overcharging the pack - or if this is normal...

I think it's normal for a fully charged pack to be as much as a volt over its rated charge. That's how smart chargers can tell when the pack is fully charged... when the voltage is higher than the nominal voltage.

[Novastar]

Something like that. For example, a "3.6"v Li-Ion pack will fully charge and read something like 4.2v.

But, that is the point. Ratings are the AVERAGE of the overall battery voltage. As you use the Li-Ion cell, its voltage will decrease from 4.2v to something akin to 3.3v. By the time it gets to 3.2v or so... the PCB kicks in and closes up shop. This prevents the batteries from dropping so low out-of-sync (if you will)... that they become unusable.

A Li-Ion pack without a PCB is doomed, as once its voltage drops below a certain level... you can kiss it bye bye.