Wild_Bill wrote:
I've been doing a lot of reading wrt battery cell testing, but have only
seen one (affordable, reasonably priced) recommendation for testing
rechargeable cell ESR.. the Bob Parker ESR Meter.

http://www.flippers.com/esrkthnt.html (near the bottom)
http://www.prc68.com/I/BatTst.shtml#EVB

I would like to be able to determine (actually see it) if zapping new
nicad cells improves (lowers) cell internal resistance, or to just check
cells for a parameter other than voltage.
From what I've found, zapping new NIMH cells isn't worthwhile, or
attempts have been inconclusive.

I want to avoid any testing equipment that requires a computer. I also
don't want to build battery packs with the newer fuel gage technology
electronics.

I'm not using the cells for any high ouput/endurance applications, I'd
just like to have a visible indication of a cell's condition.
Relying upon a tester that includes a small load resistor and a meter
doesn't give any worthwhile indication of a cell's condition.

I have a charger/discharger made by MRC for the RC hobby, with fully
selectable settings for charging/discharging rates for up to 8 cells.
The MRC Super Brain 977 has a lot of features for battery packs, and a
test of condition related to discharging at 1/5th the capacity of a cell
or the entire pack. The user monitors the voltage as it drops.
http://www.modelrectifier.com/search...ew.asp?ID=1908

I'm not trying to restore/rejuvenate old, used, weak cells. I want to
build battery packs with high capacity cells (NiMH 4500mAh sub-C,
10000mAh D) for some of my low current demand) gear, so that one pack
will last for extended field use (a full day, not weeks) without needing
pack changes.
I'll use dedicated chargers for the different packs.

I use sophisticated smart chargers for my cordless tool battery packs,
and avoid using low quality chargers.

I have Sencore Z-meters but I don't think they'll give an ESR reading on
a charged cell.


See the effect of zapping
http://www.buchmann.ca/article23-page1.asp
There are many more examples of zapping new nicad cells online.
Recommended capacitor values and voltages differ greatly.
There are a lot of opinions online that are very dated, related to
battery types that were available years ago.

A trickle maintenance approach to eliminate self-discharging effect of
NiMH cells
http://www.ka7oei.com/nicds.html

--
Cheers,
WB
.............

Your statements are contradictory. For low current applications, the
ESR of the battery should be largely irrelevant...unless the cell is
dead, dead, dead.
Why do you need to zap cells to lower the ESR unless you're discharging
them VERY RAPIDLY?

I built a jig for sorting Lithium Ion cells for ESR at a junk dealer.
Just used a DVM to measure the voltage and a switch in series with
a light bulb to limit current from a eight-cell NiMH power supply.


Just read the volts, press the switch, read the volts again.
I needed the power pack because the cells were not charged.
If your cells are charged, you can just load the cell to ground.

I had good luck matching cells for building laptop battery packs.

A Tektronix 576 semiconductor curve tracer makes a great tool for
quickly evaluating ESR of cells.

A pulse generator and a scope will measure ESR. Just look at the
amplitude of the voltage step when you hit it with the known current
pulse. You can automate this to any degree you want with a sample-hold
and a microcontroller. If you use a square wave current, you can
measure the
P-P voltage at the cell and even plot it as a function of charge level.

I tried to do this with a GPIB programmable power supply. Problem
is that the battery voltage changes continuously when you turn on the
current. To get repeatable measurements, you need to accurately control
the time between turning on the current and reading the voltage.
I couldn't make this work with all the variable latencies
in the windows OS and the GPIB controller and the supply. My
light bulb scheme worked about as well in practice.

The guys who are fanatics about this reside in the model car racing
groups. But you have to do a lot of sifting. Many people have no idea
what they're doing and just post anecdotes of how they got 100A out of
a cell with no real verifiable
experimental results.