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Thread: Batteries that have memory
www.piclist.com/techref/power/batterys.htm?key=batteries
face picon face BY : Jinx email (remove spam text)



> Is it simple chemistry or something else?

Sometimes it's just sh%#^y manufacture and maintenance. I've just
had both battery packs apart on my B&D 18V cordless drill to give
the cells a zap ** because the packs as a whole refuse to charge to
any useful amount. I mentioned, in passing, this charge issue to the
power tools staff where I got the drill from and the response was
"oh, that's memory", because that's about all they know of battery
faults

** in each pack, about half the cells showed very close to 0V after
a charge. Others had very weak charge and you'd be lucky to drill
one hole. These are not old packs and haven't had a lot of cycling.
The "charger" is just an unregulated PSU that the cells simply take
energy from. With so many dead cells in series the living can't take
all that much

One trick to re-vitalise a cell is to charge a few 1000uF to 12-15V
and dump it across the cell. This is said to break down the dendrites
(which either short the electrodes or create high series resistance, I
forget which) and prevent proper charging. After 3-4 goes at this, the
cell voltage should rise to over a volt. When all the dead cells have
been zapped the pack can go back in the charger. It's the first time
I've needed to do this for these packs, and now they charge like new

A similar principle is to hold 12-15V on the cell and remove it as
soon as the cell voltage rises abrubtly. I've tried this on other packs
in the past and it seems to work alright. Have to be careful though

<017201c8dbce$cd6e6850$89aafea9@ivp1> 7bit

See also: www.piclist.com/techref/power/batterys.htm?key=batteries
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