Charging Laptop (and other)batteries

From: Joe <rigdonj_at_intellistar.net>
Date: Thu Apr 5 23:56:36 2001

At 10:36 PM 4/5/01 -0400, larry wrote:
> This is likely elementary but many times I run across the encased laptop
>and other function(eg cordless drills) batteries. Of course each has it's
own proprietory
>charger which have long since disappeared and are costly to replace as
well as being
>device and company specific . Many of them have a 3rd terminal. What was
it's
>purpose.
> Can you recharge these batteries simply by rigging up an interface using
appropriate
>voltages and polarity ? How would you deal with the 3rd terminal ?
>
>

   Larry,

    I'm assuming that your talking about NiCad batteries. If so, the third
terminal is usually connected back to the * battery terminal via a thermal
switch. The third terminal is used to recharge the batteries at a high
current rate (Quick Charge). The thermal switch has to be in the circuit to
prevent the batteries over heating and being damaged by the high current.
You can go ahead charge the batteries at a normal 1/10 C (or lower) rate
via the third terminal or the normal * terminal. The batteries will also
last a lot longer if they're charged at 1/10 C instead "Quick Charged". The
charge voltage isn't critical in NiCads but the charging current is important.

    Joe
Received on Thu Apr 05 2001 - 23:56:36 BST