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Old 11-29-2001, 07:05 PM   #211
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Quote:
Originally posted by xray
DTM, what do you think about schulze charger?

Sorry I've never used one, so can't comment!
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Old 12-08-2001, 10:16 PM   #212
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Danny, I cycled my bats today (6 weeks since last cycle) all numbers seem to be holding true to their original numbers except 2 and I don't know if this is good bad or indifferent so I'm asking you! BTW, they're performing killer on the track so no worries just curios about the numbers. The two are:

Ds Av Vlt - was 7.07 is now 7.03
Ds Av Vlt @ 1 V - was 7.11 now 7.29

this is at 8 amp charge, 20 amp discharge.
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Old 12-08-2001, 11:03 PM   #213
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Default .85 vs .90 cutoff

Danny, I just bought some SMC 3000HVs. The label shows an avg. voltage of 1.151 at .90 cutoff. But 3000hvs batteries from another company showed 1.48 at .85 cutoff. The person at the store said the that other batteries would show a higher avg. voltage at a .90 cut off than the smc batteries I bought. Is this the case?
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Old 12-09-2001, 10:07 PM   #214
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Harshguy: I can't really explain why the voltage drops a bit but I do see this happen on some of the packs I use to test but these packs get treated real hard.

If runtime isn't critical for your type of racing then you can try traying the pack on a diode tray the voltage should come back up but the runtime will drop 20-25 seconds but it will be mostly at the end of the discharge curve.
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Old 12-09-2001, 10:20 PM   #215
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slow: First of all Thank You for choosing SMC and I hope they perform to your expectations.

In theory the voltage should be a bit lower at .85 versus .90 but the runtime should be lower.

Different types of cells react differently at the end of the cycle. The SMH's don't drop as hard as the HV's so the difference will be greater with the SMH's. The HV's drop so hard that I think there isn't more than a .001-.002 difference.

Now that being said there is more to a matched battery than just it's numbers on the stickers. The way they were matched , cycled and zapped all have an effect on the the final product and the way it will perform on the track.

I know of one company who has SMH's with inflated runtime numbers with low voltage numbers. Part of the reason why their numbers are like that is because they use .85 and the SMH dumps slower at the end of it's voltage curve. I think another reason is because they only cycle the cells once which makes the voltage lower and runtime higher. This isn't a good deal because not every cell drops or gains the same amount on the next cycle so the cells might of been matched correctly on the first cycle but once you cycle them a second time they will be mismatched.
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Old 12-09-2001, 10:59 PM   #216
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Thanks for the info Danny. I can't wait to get them on the track. I will be using them for mod sedan. Where I race a lot of people have your batteries and all I have heard are good things.
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Old 12-10-2001, 07:26 AM   #217
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Cool, well I guess my follow up question is what is the difference between the 2 numbers:

Ds Av Vlt - was 7.07 is now 7.03
Ds Av Vlt @ 1 V - was 7.11 now 7.29

Where the Ds Av Vlt went down a tad, the Ds Av Vlt skyrocketed! And next question, what's the diff between the 2 numbers, and which one means more "in the grand scheme of things"?

...I'm currently running stock so runtime ain't really an issue with these, traying sounds like the ticket ....if I was to ever swicth to mod (thinking about it for next season) ...would runtime be recoverable or once I start traying is that it?
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Old 12-10-2001, 12:08 PM   #218
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harshguy: I find it weird that your 1 volt voltage is that high. I know that my packs at 30 amps are are normally .02-.05 higher at 1 volt versus the .90 mark.

If your numbers are o.k. than I would leave the pack alone because 7.29 is extremely high but I think your T-35 might be reading it incorrectly.

My oval team guys have told me that traying and deadshorting makes the packs feel stronger on the track. My 12th scale stock guys have told me the opposite and mod guys don't deadshort or tray.
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Old 12-10-2001, 01:03 PM   #219
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Danny - I don't know much about the batt #'s and was curious.

What is the runtime difference (@30A) for a 3k NiMH (Pan or Sanyo) when using a voltage cutoff of .85 vs. .90/cell?

Likewise, how much lower is the average voltage # on the label due to the lower cutoff (again, @30A)?

Thanks.
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Old 12-10-2001, 01:29 PM   #220
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rainblows: As I posted in my earlier post it all depends on the type of cell and and how it was cycled.

I know that when we use to match SMH's that they would drop runtime and gain voltage as you put a few cycles on them. I also noticed that they don't dump as hard at the end of the discharge curve compared to Sanyo HV's. So the SMH would probably be 3-5 seconds lower at .90 vs. .85 and the voltage would be .003-.005 higher. The HV's would be 1-2 seconds lower and probably .001-.002 higher.

It seems like some companies only put one cycle on the SMH's so the voltage looks lower on the labels but the runtime is to high.

I've built a pack that was suppose to be 365 with 1.13's and it cycled out 352 with 1.14. Some might think that this is o.k. but I feel it's not because not every cell gains or drops the same as they mature in the first few cycles.

When I test a pack of SMH's that we matched I would get the same runtime with .02 voltage drop on a 4 cell pack which is about the normal drop for bars and solder. This to me makes more sense because the pack was well matched and trust me well matched packs will run stronger and stay stronger than mismatched packs.
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Old 12-10-2001, 02:06 PM   #221
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Danny - thanks for the response. It was a little confusing at first, but I think that I have it sorted out.

Let me see if I got it right. There are two separate issues you addressed. First, affect on avg voltage and runtime differences with .85 vs. .90 cutoff. Assume two cells were cycled the same
number of times and had the same avg volt and runtime, but
cell A had a .85 cutoff and cell B had a .90 cutoff. Cell A will
run about 3-5 sec shorter than B, but have about 0.003-0.005
volts more (SMHs) than B. The differences with HVs seem less.

So, given that NiMHs change so much after (runtime wise)
after say a month's use and the voltage diff is tiny, does it really
matter if .90 or .85 cutoff is used? one gives a tiny better avg volt and the other tiny better runtime.

Second, you say number of cycles a matcher uses before labelling a cell is important. I agree. But that wasn't what I was questioning with the .85 vs .90 issue.
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Old 12-10-2001, 03:10 PM   #222
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slow: Yes you have it figured out correctly.

I know that you didn't ask about the number of cycles but that is very important to match correctly and to get real numbers.

Company X cycles there cells more than once and sell a pack with 365 seconds at .90 and then compnay Y puts one cycle and sells a pack of 380 at .85. In the end they both have the same runtime.
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Old 12-10-2001, 03:33 PM   #223
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Danny - ok. thanks.

I think you made an error? A 365s (@ .90 cutoff) label would be the same as a 370s (@ .85 cutoff) label for SMHs (only max 5 sec diff from your post, not 15 sec). And the .85 cutoff labelled cell would have higher voltage right?

Again, if I was going to buy SMHs or HVs, the .85 vs. .90 cutoff doesn't seem to be much of a difference (at most 3-5 sec for SMHs and none for HVs), assuming they are cycled the same # of times.
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Old 12-10-2001, 03:43 PM   #224
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Rainblows: after a few more cycles, that 380 pack would have been down to a 365 pack anyway. That is the point that Danny was making.
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Old 12-10-2001, 04:00 PM   #225
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Ovalman - I see you're confused like me also. Assuming both cells were cycled the same # of times by the same matcher, but he used .85 on one cell and .90 on the other, why should one cell drop 15 sec, but none on the other after some use?

Sorry to be asking so much, but I'm considering getting some 3Ks and with the price so high per pack, I want to make sure that I know what the #'s mean.
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