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Old 04-19-2003, 01:30 PM   #31
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Ok, here's the figures I have, taken from my 1 matched pack and my 2 "unmatched" packs

These are from the second cycle of the day (gave them a wake-up cycle first, which gave slightly lower voltages).

Pro-trak settings are... Charge 4A, Delta 0.03v, Discharge 20A, Cutoff 0.90v per cell

35 Pack 1

Time 644
Av1 (which is average voltage over first 120secs) 7.47
Av2 (average voltage over rest of discharge) 6.86
Cap 3577
Pack Match 90%
Worst cell 75%

35 Pack 2

Time 635
Av1 7.47
Av2 6.87
Cap 3527
Pack Match 90%
Worst 71%

60 pack

Time 640
Av1 7.43
Av2 6.81
Cap 3555
Pack Match couldn't be done as one cell reached 0.50v (Pro-trak's reversal protection cutoff)

I should say that the 60 pack has had about 6 more cycles on it in my hands.
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Old 04-19-2003, 02:46 PM   #32
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Very interesting. Thanks.
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Old 04-20-2003, 06:50 PM   #33
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Sosidge, what do you think of that matched pack? I mean, it seems like production tolerances are getting better and better, but I would expect a matched pack as being at least as good as a non-matched pack?

I'm not familiar with ProTrak chargers, and I cant really figure out the "Pack Match 90%, Worst 71%" - what do the percentage refers to? Is it relative to the best cell? And is it based on voltage or what?

Thanks.
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Old 04-21-2003, 04:48 AM   #34
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All the packs feel about the same on the track - the matched pack is no better, and no worse. I only race stock though so I'm never pushing to the limits of the capacity.

I'm not totally sure what the pack match is based on - I don't think it's super-intelligent, I think it's based on the cell voltage when the discharge cuts off more than anything else. So it's a guide to whether one of the cells is dumping early or not.

The only drawback of a non-matched pack, as far as I can see, is the risk of getting a bad cell, but I think these Schumachers have already been tested (not sure though).
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Old 04-21-2003, 04:58 AM   #35
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Matched versus unmatched; Well, it would be nice to have some good equipment to test with and draw curves etc. And a lot of packs to test on

From what I've seen and measured on some pretty old Orion matched cells, they got good performance, even after a lot of use. Maybe a matched pack last longer?

However, I find that an active equalizer do a good job in preventing getting a bad cell. I havent got one yet, after almost 3 years. And the first year, I abused my packs, since I only got 2 NiCd packs and no equalizer. When I started using the equalizer after a year, it really improved performance.
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Old 04-21-2003, 06:57 AM   #36
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The equalizers are critical to battery life.

Even in a matched pack, the cells are not identical. Discharging the pack down to .9 per cell is done only by average. No charger that I know of has leads for each individual cell. In this situation, it is possible that one cell is down to .5 and another is at 1.0. When you go to charge that pack, one cell is much closer to being peaked. As you continue this cycle, cells will get damaged.

By using an equalizing tray, you dump each cell individually to near zero charge. This will allow for a more effective charge and less abuse on some of the cells.

With NiMH packs this is done differently than the old NiCDs. You tray them just before you charge. This should extend the life of both matched and unmatched packs.

Jeff Gilligan
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Old 04-21-2003, 07:55 AM   #37
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Quote:
Originally posted by gotpez
The equalizers are critical to battery life.

No charger that I know of has leads for each individual cell. .............
Jeff Gilligan
The Protrak charger has....it's not perfect, but there are some things it does quite well.
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Old 04-21-2003, 09:51 AM   #38
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Default Is the need for matched cells becoming a myth?

FACT: Matched cells will ALWAYS be better and more Expensive than UN-matched Cells.If your Racing and using UN-matched packs, there is NO WAY you are going to be able to keep up with the People who are using better Batteries.

If your Charger allows charging of a single cell, you can just clip across the Battery Bars to isolate an individual cell for testing. Works fine, and you can find weak cells very easily this way.
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