Andy wrote:
I was just looking through the Mar/Apr issue of Wood magazine, where
they did an article on myths of rechargable batteries. One thing they
said really confused me - they said that rechargable batteries should
NOT be discharged completely, and that you should recharge them as soon
as you feel your tool slowing down, because if a cell is totally
discharged it can switch polarity and ruin the whole battery (or
something like that). I'd always heard that with NiCad batteries, you
DO want to discharge them completely, so they don't develop a 'memory'
and accept less of a charge each cycle. Does anyone have a good
explanation for why one or the other is true, or firsthand experience
trying it both ways?
Also, they said that NiMH batteries are really not superior, because
even though they can have larger amp-hour ratings, they don't last for
as many charge/discharge cycles. I'd also read elsewhere that NiMH
batteries don't develop a memory, which seems to me like it would make
them last longer. Has anyone used both types side-by-side through the
whole life of a battery?
TIA,
Andy

Greetings,

NiCad battery memory problem can only occur under special circumstances,
which never occur in how any one uses NiCads, so don't worry about it.

You do want to discharge a cell, but not reverse the polarity.
A battery has many cells. Take the battery voltage and divide by
1.3 to get the approximate number of cells. If you have a 14V
battery pack, you do not want the voltage to drop more then 1.3 Volts.
If more than that, you have a good chance of reversing the polarity
on one of the approximately 10 cells.

Nicads have a fairly constance Voltage until they reach the discharge
level, then the Voltage drops quickly. If you start the recharge
just as the Voltage drops, i.e. when the tool starts to slow, then
you recharge when the battery has mostly discharged.

People have done side-by-side testing. Let's hope they reply to
your posting with the results or references to the results.

Sincerely,
Bill Thomas