On Sun, 14 Aug 2011 10:58:33 -0500, Jim Yanik
wrote:

OTOH,the B&D Dustbuster I had was designed to stay on the charger when not
in use,and it lasted 10 years before I had to have another NiCd pack
installed. that new pack lasted almost as long.

My Dustbuster battery died after about 2 years of sitting on permanent
charge. I didn't investigate. I installed a home made battery pack
about a year ago. Works fine. I think the original batteries may
have had a problem.

I've seen NiCds listed at DigiKey specifically intended for staying on the
trickle charger when not in use.

Never heard of such a thing, but I'll look.

What creates the problem is that many vendor rate their drills,
laptops, and devices by how long it will run on battery power. In
order to improve their numbers, they try to cram as much charge into
the battery as possible. That works well enough with a new battery,
but as the battery gets older, the table driven and timer charge
controllers start to overcharge. That causes heating, which is an
invitation to a premature demise of the battery.

In my never humble opinion, there's only one correct way to charge
batteries, and that's with a "coulomb counting" charge controller. It
measures the current in, runs tests on battery capacity, and adjust
the charge current and timing as necessary. They can programmed for
almost any desired attribute (long battery life, fast charging,
conservative capacity, etc), and will compensate for battery aging.
Many of the charge controller chips made for LiIon will work for NiMH.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558