[Shop-talk] 18v battery dead? Reviveable?

[Randall]

> Anyway, now the battery won't charge.  I seem to recall 
> something somewhere saying that if you drain it all the way 
> dead, the charger won't recognize the battery on there and 
> won't try to charge it?
> 
> Is that right?  How do I convince it to try charging anyway?

My Ryobi charger is like that.  To work around it, put a little charge into
the battery some other way.  If you can figure out which terminal is which,
an ordinary 12v automotive trickle charger will probably do.  I use my
adjustable bench supply.

> Or, did I just really kill this battery and I should write it off?

Unfortunately, it's likely that one or more cells is now shorted.  Running a
pack completely flat reverses the voltage on the weaker cells, which can
cause crystals to grow and short the plates.  There are potentially ways to
(partially) recover shorted cells, but they require disassembling the pack
and zapping the shorted cells with high current (from a capacitor).

Randall