Re: ?? rechargable dry cells

 
The AA Energizer NiMH cells I use in my solar lights work fine.

Do you have a proper charger for them?

 
Regular NiMH batteries have a poor self-discharge rate.  In low-drain
applications they lose most of their power through just sitting
around.  They are ideal for applications where you expect to be
recharging them every week or two but not for things where you expect
them to sit on a shelf for a month or two and then work well.

Eneloop and other low self-discharge NiMH batteries work much better
for low-discharge tasks.

You should also get a good charger.  The "free" chargers bundled with
batteries are usually awful.  At the very least you need a charger that
has separate charging circuitry for each cell; otherwise you will
always be over or under charging some of the batteries.

Maha makes some great chargers and the LaCrosse BC700 & BC900 chargers
are also very good.  In addition to separate charge circuits, advanced
chargers also allow multiple charge rates (slower charges (8hr+ for AA)
are better for battery longevity, but sometimes you are in a hurry),
displays to show the status of each battery and special modes to do one
or more discharge/recharge cycles that can rejuvenate dead batteries.
--
Jim Prescott - Computing and Networking Group    jgp@seas.rochester.edu
School of Engineering and Applied Sciences, University of Rochester, NY

 
I suspect that the rapid-charge feature is what is causing your problem.  I have
an old (5+ years old) NiMH / NiCd switchable charger that takes several hours to
fully charge them.  Each pair of cells is on a separate circuit.


The operating life of the NiMH's is at least 4x the life of the NiCd's they
replaced, which correlates with their respective mAH ratings.  In the solar
light installation, the NiCd's would not last a full winter night unless the
previous day was sunny.  The NiMH's lasted 4-8 nights on the longest nights of
the year, depending on the amount of sunlight during the days.


Yes.  I wouldn't use a rapid charger for installations where I wanted maximum
battery performance...  That charger could also have reduced the cells' ability
to retain a charge in any case.

 
:I use NiMH AA cells in mouse(s), wireless earphones, camera, CD player,
: etc and AAA cells in digital recorder/mp3 player. Compared to ancient
: NiCADs, performance of the brandname 2500mAh product I'm using is dismal
: and I'm tired of fooling with it/them. Anybody have positive experience
: with any alternative product that (s)he can recommend? For me, longevity
: and performance take precedence over purchase price.

Part of the problem may be that NiMH cells don't have the same
charge/discharge parameters as 'standard' disposable batteries.

Add to this the wireless device may not work to the full discharge point of
the NiMH battery.

 

Anything like a mouse which spends most of its time sitting around on
is going to be a very poor application for nimh batteries.  Also, that
15-minute charger you mention in a later message is a piece of junk.
My batteries work a lot better now that I've given up on it and went
to a regular charger.