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
Older and cheap NiCads will suffer the memory effect (the correct term is
memory effect as they don't actually develop a memory they just show
symptoms of it). As NiCads were improved the memory effect was worked on
and is pretty much non existant. For example the pair of batteries that
came with my 1995 makita drill I almost never fully discharged and they
lasted until 2003.
NiMH and Lithium ION do last fewer complete discharge cycles, however it
takes many partial cycles to make a complete cycle therefore you can top
them off many many times, in fact its better to charge them each time you
use them rather than waiting for the drill/saw to slow. I still see people
fully discharging and recharging their laptop batteries or pulling them out
of the laptop and storing them then wonder why they don't last more than a
year or two while my always in and topped off last 4-5 years.