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Old 12-09-2008, 01:15 AM   #1546
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Okay, here are my results after storing the packs for over 7 months. These were the original 4000 packs when they first came out. Great for club racing. The previous cycles are posted in quotes at the top of the page. The first 2 cycles I did on each pack this month are at 1C or 4amps. After that, I went to 2C (8amp) charge rates to speed up the process. According to Danny, if I read correctly, this should not affect my numbers. Next week I'll switch back to 4amp charge to see if they change my results.

12/6/08 (very first cycle after 7 month storage)
Pack 1
406 seconds 7.28v
3947 mAh 8.3 IR

Pack 2
401 seconds 7.29v
3898 mAh 8.5 IR

12/6/08 (cycle 2)
Pack 1
408 seconds 7.30v
3966 mAh 8.0 IR

Pack 2
402 seconds 7.30v
3908 mAh 8.4 IR

12/7/08
Pack 1
407 seconds 7.32v
3956 mAh 7.5 IR

Pack 2
403 seconds 7.32v
3918 mAh 8.2 IR

12/8/08 (cycle 1)
Pack 1
407 seconds 7.31v
3956 mAh 8.1 IR

Pack 2
400 seconds 7.32v
3888 mAh 7.7 IR

12/8/08 (cycle 2)
Pack 1
407 seconds 7.31v
3956 mAh 7.8 IR

Pack 2
402 seconds 7.31v
3908 mAh 8.3 IR

12/9/08
Pack 1
406 seconds 7.32v
3947 mAh 7.6 IR

Pack 2
401 seconds 7.32v
3898 mAh 7.6 IR

So here you can compare numbers from the quotes at the top of page. They include the numbers on the box when they were new. Also noted, today/tonight on my last cycle, I check the voltage on each cell. After discharge, Pack 1 had one cell at 3.09v and the other at 3.43v. After 1000 mAh put back into them for storage, one cell had 3.76v, the other was 3.77v. On Pack 2, after discharge, one cell was at 3.09v and the other was at 3.55v. After 1000 mAh was put in for storage, one cell had 3.77v and the other was 3.78v. I'm thinking I need to balance them.

What's the cheapest way to balance them? Or cheapest balancer?

Anyways, just thought this info might be useful somehow. I'll keep cycling them every week. Maybe I'll heat them a few times and see how they react to that.

Enjoy....
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Old 12-09-2008, 02:11 AM   #1547
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Thanks for the info Jimmy. I was looking for some numbers. I can tell you if you heat the packs the IR will go down and the Avg. Voltage will go up, this has been proven. But watch out for your pack swelling if it gets too hot. I will try to post some numbers with packs I have been running for about 7 months so they have over 200 cycles on them and I would be curious to see how they compare. I am off tomorrow so I will tend to some battery needs then.

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Old 12-09-2008, 06:02 AM   #1548
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Don't try heating your packs!
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Old 12-09-2008, 09:14 AM   #1549
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Quote:
Originally Posted by John St.Amant View Post
Don't try heating your packs!
John,
I know you are a nice guy in person, but don't come on here and flood a thread for a companies product. If you don't want to do something, don't do it. It's just that simple, if something clearly wasn't safe, it wouldn't be done.

I have been heating my packs responsibly for almost a year. The performance increase is absolutely incredible. Heating the pack to a certain temperate such as 125 degrees, when done correctly aka, only about a half hour before you run, is totally acceptable. If you think you may forget, go to a lower temperature such as 110 degrees. This has been done by MANY MANY MANY racers, and pilots! I do the same thing for helicopters and its a dramatic increase in power! These same packs have the same, if not better numbers than 6 months ago, so heating must be ok huh?

Please to anyone coming onto this thread, it is for SMC's products and info about them and how to treat them. Danny will not tell people to do something they are not comfortable with.

If you want to stick to the basics, Great! The packs still run way above many others, but if you want the maximum performance, you will be heating before you run.
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Old 12-09-2008, 09:38 AM   #1550
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I'm trying to keep a safe sport safe and above all cost effective . Spending more on tech isnt what this is supposed to be about . We are just starting to get rid of failing NiMh batteries and countless dischargers. Those of you who still have them might be good to adapt them to your kids toys. All I'm trying to say is keep it simple stupid. These are the sort of things that killed slot car racing. The true spirit of competition is we all have the same equiptment. Too many people going faster than they can handle already. So heat your packs.. cool your motors. Bust out a can of freon 'cause you are going to get a free tenth.... but God forbid you just charge 'em and race.
The cars are fast enough. We need to tighten up on these things or it will get out of hand again and again. Tire warmers! Battery warmers! Responsible or not... some one some where something will fail and cost someone else something valuable. Mark my word!
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Old 12-09-2008, 12:45 PM   #1551
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John, I use to heat my packs in the past with tire warmers. So it's nothing new to me. I'm fully aware of what it does and the precautions. I just want to see if it'll help "rejuvenate" my packs.

Casey, do you have the 4000 packs? Curious to see your numbers too.
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Old 12-09-2008, 01:39 PM   #1552
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Hey guys! Dont get me wrong here. I'm only trying to avoid a situation. I believe that all the venues should mandate a voltage and temp. of battery durring tech. Seems that if no one does it theres no issues for anyone anywhere.
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Old 12-09-2008, 02:18 PM   #1553
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Jimmy,
It's normal for cells to be off after a discharge cycle. The only way to test for balance is at the end of the charge. So do a charge only and measure the cells. If they are within .02 or so they are fine. Based on the storage charge voltage I think your cells will be very close after a full charge.

Your results seem to show what I have suspected about storage charge and inactivity of Lipos. The increase of 1 milliohm isn't much and probably doesn't reflect any difference on the track.

Thanks for the info and I'm glad to see that after 7 months or so the change isn't that much. So the change seems to happen then not get worse over time as 7 months is pretty long.
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Old 12-09-2008, 02:23 PM   #1554
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One thing I did notice is that if you heat a pack that has gotten higher in IR due to cycle life or an other issue it will have a better gain in performance than a new pack with very few cycles. So the new pack doesn't drop as much in IR when heating it than an older pack with numbers that have deteriorated.
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Old 12-09-2008, 02:53 PM   #1555
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It'd be interesting to see how a nimh pack deteriorates after 7 months of dormant storage.
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Old 12-09-2008, 03:02 PM   #1556
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Actually the newer generation sub-c cells of ther last 3 years or so would not hold up longer than 3 months with a full charge. Our newer EnerG cells from the middle of September actually have a much better selfdisharge profile and will hold up to storage much longer than previous models. That being said its a few years late as Lipos are still easier to handle and take care of.

On the subject of heating I think that it shouldn't be done as it's one extra thing that racers need to worry about. My feeling is that if everyone does it it would be the same if no one does it. So this would keep things simpler at the track. With Lipo and BL electric racing is much easier than ever and we need to keep it like that.
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Old 12-09-2008, 03:17 PM   #1557
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Danny, are you still saying it's OK to charge at 2C or more ?
Thanks.
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Old 12-09-2008, 03:39 PM   #1558
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Yes our packs can be charged at 2C and this is what I use when cycling my packs.
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Old 12-09-2008, 07:02 PM   #1559
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Cycled my pack that had been stored at 6 volts for 5 months today. These are first cycle, 1c, heated to 140 degrees, discharged at 35 amps.

SMC 5000 28C

7.47 AV
5.3 IR
519 S

7.46 AV
4.8 IR
566 S

Absolutely stellar!
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Last edited by StephenSobottka; 12-09-2008 at 08:39 PM.
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Old 12-09-2008, 08:25 PM   #1560
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Cycled all three of my 4000 packs today and here are the results. Charging at 6 amps and discharged to 6 volts on a turbo 35 gfx. Packs 1 and 2 have about 200 to 250 runs and pack 3 about 50.

Pack #1
Seconds-404
Mahr-3927
Average Voltage-7.28
I.R.-8.4

Pack #2
Seconds-400
Mahr-3888
Average Voltage-7.26
I.R.-9.3

Pack #3
Seconds-399
Mahr-3879
Average Voltage-7.33
I.R.-7.6

Clearly the first two packs are deteriorating but not terribly. The performance difference on the track from 1 and 2 to pack 3 is equivalent of about a .05 per lap.

I have had the first two packs since around March 2008 and race every weekend.
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