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From: mike on 15 Jan 2010 14:21
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/product-view.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.
From: John Robertson on 16 Jan 2010 02:00
Wild_Bill wrote:
> Phil, thanks for the concise, definitive reply, very much appreciated.
>
> I have a milliohm meter around here somewhere, but I don't know if it
> would work for battery cells, and I can't remember the meter's
> resolution, either.
> It's one of the digital display meters that are handy for checking
> circuit board traces (with a variable audio tone) and other low
> resistance measurements. The pitch of the tone gets higher as the
> resistance gets lower.
>
> --
> Cheers,
> WB

Please let me know the results of your experiments so I can update my
page on Bob's ESR meters and battery ESR.

John :-#)#

> ..............
>
>
> "Phil Allison" <phil_a(a)tpg.com.au> wrote in message
> news:7rccu7F41tU1(a)mid.individual.net...
>>
>>> 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)
>
>
>>
>> ** As you can see form the attribution - that article is one of mine.
>>
>> Bob's ESR meter will not be much use for high capacity cells that have
>> only a few milliohms of ESR - as the lowest reading on the display is
>> 10mohm
>>
>> However, a pack of 4 or more cells would likely be testable and reveal
>> poor connections of the existence of a bad cell.
>>
>>
>> .... Phil
>>
>>
>>
>


--
(Please post followups or tech inquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
From: John Robertson on 16 Jan 2010 12:49
Gerard Bok wrote:
> On Fri, 15 Jan 2010 19:14:44 -0500, "Wild_Bill"
> <wb_wildbill(a)XSPAMyahoo.com> wrote:
>
>> I have a milliohm meter around here somewhere, but I don't know if it would
>> work for battery cells,
>
> Unless you are very sure that your milliohm meter is capable of
> testing battery cells, I would strongly advice you not to try it.
>
> General rule: don't apply anything 'active' to a device that is
> supposed to measure resistance.
>

While that is true for older analog meter movements (always measure
resistance with system power off) modern meters such as the Bob Parker
ESR meter can read the resistance of a 'hot' circuit up to the breakdown
voltage of the input capacitor (roughly 50V). As such a meter like the
Bob Parker ESR kit (Blue ESR now produced by Anatek) can easily be used
for testing the internal resistance of batteries - the question is if
that produces useful information!

John :-#)#

--
(Please post followups or tech inquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
From: mike on 18 Jan 2010 19:32
Phil Allison wrote:
> "mike"
>
>>>>> ** Wow - 0.1mohm resolution.
>>>>>
>>>>> Those test probes will sure have to make GOOD contact with the cells.
>>>>>
>>>>>
>>>> Why?
>>>
>>> ** Huh ?
>>>
>>> The comment EXPLAINS itself.
>
>> Assuming I RTFM'd the right manual, it's a Kelvin probe.
>
>
> ** What planet are you on ??

Obviously, not the one you're on.
>
>
>
>
> .... Phil
>
>
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