SISC wrote:
Hi out there in cyberspace,
got a bunch of power batteries for various batt.operated tools and other
things.
After some cycles of charging and discharging some deteriorations of holding
capacity can be noted ;some before their
time of reasonable lifecycle. Yes a good charger will prevent improper
charging.

However most of these powerpacks consist of numerous individual cell like
subC etc.
Do I assume correctly, that if a powerpack goes down ,not all individual
cells are to blame and some me be still quiet
allright und of further use?
How can someone check out which one to toss(into recyclebin) and which one
to reuse?
Any idea if evaluation can be accomplished with DMM or any specific
procedure?
I think many friends out there might be intertested to learn about!
Please reply to forum to enlighten (me) !
Thank You MS



Consumer grade devices are designed with the cheapest/worst quality
cells available and charged with the cheapest/most abusive charger
available. High drain applications like drills are particularly hard
on batteries. By the time the drill starts to slow down, you've alredy
reversed a cell. And we just gotta finish that hole...and only one
more... and the pack is toast.

I've wasted months of my life over the years trying to make one good
battery pack out of two bad ones.
If the drill drills holes, use it. If it don't get a new pack or replace
ALL the cells with new ones. This will cost you more than a new pack
if you use good quality cells.

If you're intent on using dead cells, here's what I'd do.
If there's any white powder around the contact, throw it out...it's vented.

Measure the voltage of each cell. If it's zero, put it aside to worry
about later. Anything but zero is good. Zero is ok if the battery
hasn't been used for years, but it's usually a bad sign.

Charge 'em all up at C/10. (That's 100 mA or so for a cheapo
Sub-C cell). for 16 hours.
Measure the voltages. If any are much lower than the rest, throw them out.
Let the rest sit on the shelf for a week.
Measure the voltages again. If any are much lower than the rest, throw
them out.
Build yourself a 1 Amp or so current source. Car tail light and a car
battery in series works.
Put your meter on the battery and measure the voltage.
Then apply the current. Quickly note the new voltage. Subtract to get
the difference. This is a measure of the internal resistance of the cell.
This measurement is all very sloppy, but after you've measured a few,
you'll get a feeling for the voltage difference for a good cell vs. a
bad one.

Throw out the ones that have significantly higher delta-V.
This takes some experience and experimentation. Once you get
a handle on what the numbers should be, it'll go quickly.

If you have any cells left, you might have a chance of using them
in something. It's almost impossible to tell the capacity of cells that
look the same. When you put them in series, the weak one reverses first
and things start going downhill fast. Fast charging is also a problem
cause you can EXPLODE one before the charger senses termination.
Ask me how I know...

If you want to add to your pain, go back and work on the cells you
culled out at various stages of the process.

And DO NOT solder on cells. If you cut the tabs so there's a little
left on each end, and they're solderable, you can solder to the tabs.

There's gonna be a snowstorm of people telling you soldering is OK,
there always is, and how many hundreds of cells they've soldered.
I've soldered a few hundred myself, but results on the first few
weren't all that good.
My yield went WAY up when I got a tab spot welder.
Just don't do it.
mike


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