stryped said:
It just quit working. Even after charging overnight. I got some sort of
error beeping on my charger too.
I have a voltmeter and know how to use it. I can solder but am not the
world's greatest although never "blew" a battery open. Can you explain
how that works one more time?
What are the chances that just one cell is bad and needs to be
replaced? Seems like that would be a cheap fix.
It's common for a single cell to fail, usually by going into reverse
polarity or by developing an internal short.
Reverse polarity can be fixed by charging just that cell alone. You'll
need a source of DC voltage higher than the 1.25V of the cell and a
resistor in series with it to limit the current (50-200mA for a
C-cell). You can even use an alkaline cell with a 5-10 ohm resistor in
series with it by connecting them for about 30 seconds and then
charging the whole battery pack normally.
A shorted cell can sometimes be fixed by zapping it with brief pulses
of higher voltage, like 12-50V, from a capacitor (connect "+" of cap
to "+" of cell, "-" of cap to "-" of cell) to vaporize the short, but
almost always the short grows back in a few days. I zap until the
popping sound from the arc weakens, which I think indicates that the
short has disappeared.
To solder in a new cell you'll need an iron with plenty of power, at
least 40W, but 45-50W is better, and it helps a lot to sand the ends of
the cell and apply some rosin flux (not acid flux) to it. I would tin
any wires before soldering it to the cells, but it's possible that
there isn't enough room inside the battery case for decent size wire,
so you may have to instead use strips of copper or brass (from a hobby
shop or real hardware store). Try to complete the soldering quickly,
to prevent damaging the cell from heat. This is why you want to use
the 40-50W iron, sand the metal, use rosin flux, and tin the wire or
metal strips.
