Battery UM08A71 not charging. Got inside the battery pack without too
much colateral damage. Put a bit of current limited charge into the
cells and retried but the same.
I did not expect a computer inside a battery. 24 pin bq29312APW and a
labelled over memory? of 38 pins etc.
What I thought would be the pass powerFET was a heated fuse , marked
12AH3, presumably

http://www.cyntec.com/product/protec...543212AH3C.pdf
I've never come across the like. Looks as though the heater has failed.
So why the heater? Fast fusing of metal in overload situation if its
already close to fusing? It is designed specifically for L-ion cell use.
I assmue this PC in a battery monitors for heater failure and then
locks out from charging.
There does not seem to be independent monitoring of the 3 cells. There
is a thermistor , well something that is 7.8K sitting there. What would
be the kapton covered piece of thin ribbon going to the ,still mounted,
unobserved side of the middle cell.
Seems the powerFET is 2 off p-ch , marked A2715, 8 pin devices = NEC
uPA2715 ?

Got further into it and made good contact with the fuse thing and its
heater at 7.8R is ok. The foil plus another is tap-offs from the 2 other
cell joints so individual monitoring/charging?. Another SMD 4 or 6
pins,skew view, as longish and lumpy perhaps a crystal ,marked
Q5B
H8
463

The heated fuse principle would seem to be used as a crowbar
http://ip.com/IPCOM/000004821#

I'd not current and voltage limited external charging of the battery to
high enough minimum voltage. Needed at least 10.5V for this 11.1V
battery. Now taking charge from the notebook and all working normally.
Next time a similar fault , I'll try just melting holes in the battery
casing to make contact with the cell ends and not separate the casing
into 2.