29 May
1998
29 May
'98
2:25 a.m.
On May 29, 6:53, Joe wrote:
Cord wrote:
>I just picked up an older style laptop that I need
some hlp on. It is
>a Toshiba T2200SX laptop.
>1) I need a battery for this unit. I have the
power supply, but the
>battery with it won't charge.
Your chances of finding another battery are slim.
Even if you find one
it will be old and probably won't last long. My suggestion is to take it
to one of the battery places that rebuild batteries and have them replace
the cells in your old battery.
If you can take the battery pack apart (separate it into single cells) in
such a way that it could be re-assembled, all is not lost.
The usual problem with NiCds is that internal crystal growth makes short
circuits; the battery will show virtually 0V. If you force a sufficiently
high current through the cell, it will often remove the short. However,
the current needs to be very high, and has to be of short duration to avoid
other damage.
The way I do it, is to charge a large electrolytic capacitor up to 20V -
30V, connect one side to one end of a cell with a short thick wire, and
touch ("flash") the other side to the other end with another short thick
wire. The spark is usually fairly dramatic, so it's best to touch the wire
to the terminals and not the case (lest the arc burn through it), and use
eye protection. Repeat as required until the cell shows some reasonable
voltage.
Then put the cell through a full-charge/deep-discharge/full-charge cycle.
I've resurrected quite a few NiCds with my 24V bench PSU and a 50,000mfd
30V electrolytic.
BTW, inside a lot of laptop batteries, you'll find a small metal box in
series with the cells. Don't throw it away; it's a thermal cutout intended
to prevent excessive current flow.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York