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Old 04-21-2008, 11:04 AM   #571
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that seems like a lot of difference on the IR number between the 4000 and the 5000.I am glad I purchased the 5000.Am I looking at this wrong?
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Old 04-21-2008, 11:21 AM   #572
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It's normal for a smaller pack to have higher IR and lower average voltage. When it comes to Lipos the bigger the cells the better they tend to be. This is why it's important to have a maximum size rule like ROAR decided to do.
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Old 04-21-2008, 11:23 AM   #573
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What do I need to set my voltage cutoff at for the 4000 pack?

Thanks
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Old 04-21-2008, 11:52 AM   #574
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I assume you mean for discahrge as for charge you need to use a CC/CV charger. For discharge you should use 6 volts.
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Old 04-21-2008, 12:33 PM   #575
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Quote:
Originally Posted by racenut123 View Post
that seems like a lot of difference on the IR number between the 4000 and the 5000.I am glad I purchased the 5000.Am I looking at this wrong?
Quote:
Originally Posted by Danny/SMC View Post
It's normal for a smaller pack to have higher IR and lower average voltage. When it comes to Lipos the bigger the cells the better they tend to be. This is why it's important to have a maximum size rule like ROAR decided to do.
I had noticed the same thing as racenut but was assuming it had to do with cell size/capacity or some such which Danny's response seems to confirm.

My question would be this...Danny's answer describes using the maximum size (capacity) cells allowed, but the voltage increase proved fairly marginal in this case. The way I'd look at it (not necessarily the RIGHT way to look at it, mind you) would be that I would have gained 1/2 of 1% in voltage for an addition of a little over 3% increase in total vehicle weight (45g against the 1418g minimum for foam TC...slightly less percent if using the rubber TC weight). To me that seems a questionable trade-off if the additional mah capacity isn't needed. In fact for me it tipped the balance to the smaller capicity cells with their lighter weight.

Now, this certainly assumes a few things:

Firstly, and I'm WAY open to correction, while low IR is probably good it is higher voltage and/or longer run time where the "rubber meets the road" so to speak.

Secondly, that I DON'T need the additional 1000mah of capacity for 5 minute heats. If we end up increasing heat lengths this may or may not fall by the wayside.

Third, and possibly most important, there isn't already 45g of ballast being added to "make weight". In my particular case I am not, so that 45g "in hand" is significant.

These were the reasons I went with the 4000 packs. Curious if my reasoning stands or is invalid.
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Old 04-21-2008, 02:36 PM   #576
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Danny, please remember to include the actual discharge rate for those who aren't in the know when providing data's.

Also would you be willing to provide starting and ending temps for my own reference. That also is an important factor in providing those kind of data's. Thanks again.
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Old 04-21-2008, 04:05 PM   #577
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Quote:
Originally Posted by Scottrik View Post
I had noticed the same thing as racenut but was assuming it had to do with cell size/capacity or some such which Danny's response seems to confirm.

My question would be this...Danny's answer describes using the maximum size (capacity) cells allowed, but the voltage increase proved fairly marginal in this case. The way I'd look at it (not necessarily the RIGHT way to look at it, mind you) would be that I would have gained 1/2 of 1% in voltage for an addition of a little over 3% increase in total vehicle weight (45g against the 1418g minimum for foam TC...slightly less percent if using the rubber TC weight). To me that seems a questionable trade-off if the additional mah capacity isn't needed. In fact for me it tipped the balance to the smaller capicity cells with their lighter weight.

Now, this certainly assumes a few things:

Firstly, and I'm WAY open to correction, while low IR is probably good it is higher voltage and/or longer run time where the "rubber meets the road" so to speak.

Secondly, that I DON'T need the additional 1000mah of capacity for 5 minute heats. If we end up increasing heat lengths this may or may not fall by the wayside.

Third, and possibly most important, there isn't already 45g of ballast being added to "make weight". In my particular case I am not, so that 45g "in hand" is significant.

These were the reasons I went with the 4000 packs. Curious if my reasoning stands or is invalid.
Scottrick,
I think your reasoning is valid assuming you are over legal weight with a 5000. I am under weight with the 5000 so run it in stock. In mod I run a 4000 since I can actually lower my cog by running a smaller batt.
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Old 04-22-2008, 01:35 AM   #578
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Quote:
Originally Posted by 4wd Racer View Post
Danny, please remember to include the actual discharge rate for those who aren't in the know when providing data's.

Also would you be willing to provide starting and ending temps for my own reference. That also is an important factor in providing those kind of data's. Thanks again.
The discharge rate is 35 amps which is the max using the T35GFX. The temperature was 72 degrees at the start of the cycle and I didn't think of measuring the end temperature.
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Old 04-22-2008, 02:37 AM   #579
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Okay, I did a cycle tonight. I raced Saturday. So the packs sat for a day or two without touching them. Pack 1 IR went up as expected. But Pack 2 went down. I'll cycle again tomorrow night and Pack 1 IR should drop back to normal. But I'm curious as to what Pack 2 will do. I do notice run time slowing going down. But that might be due to me charging at 12 amps. I'm gonna go to 8amp charge for racing and see what happens. Plus now I'm starting to heat up my packs after charging. Of course all my cycles are 1C at 4000mAh or 4amps. 35amp discharge with 180seconds cool down for the cycle. Packs are discharged down to 6v before cycle starts. Here's the history so far. Each packs usually get 3 runs on race day. 1~2 cycles during the week. So about 4 or 5 charges a week for each pack.

On the box,
Pack 1;
415 seconds 7.34v
4034 mAh 7.1 IR

Pack 2;
409 seconds 7.35v
3976 mAh 7.2 IR

4/8/08
Pack 1;
422 seconds 7.32v
4102 mAh 7.5 IR

Pack 2;
416 seconds 7.33v
4044 mAh 7.5 IR

4/9/08
Pack 1;
420 seconds 7.34v
4083 mAh 7.2 IR

Pack 2;
416 seconds 7.33v
4044 mAh 7.2 IR

4/13/08
Pack 1;
417 seconds 7.35v
4054 mAh 7.2 IR

Pack 2;
413 seconds 7.35v
4015 mAh 7.1 IR

4/22/08
Pack 1;
416 seconds 7.34v
4044 mAh 7.5 IR

Pack 2;
410 seconds 7.35v
3986 mAh 6.9 IR
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Old 04-22-2008, 08:18 AM   #580
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The outstanding performance of your batteries has really given LiPo popularity a shot in the arm. Nobody even mentions NiMH anymore.

Get these things legal for IIC!
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Old 04-22-2008, 11:22 AM   #581
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JimmyMac if your able to get your packs hot prior to using them there really is no need to charge them at 12amps. A regular 5 or 6 amp charge should do give you the same results.

I think a decrease in capacity overtime is to be expected. As long as the voltage stays up and the IR down the packs should be fine.
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Old 04-22-2008, 11:23 AM   #582
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Quote:
Originally Posted by syndr0me View Post
The outstanding performance of your batteries has really given LiPo popularity a shot in the arm. Nobody even mentions NiMH anymore.

Get these things legal for IIC!
I personally feel they should be legal for the IIC but I don't make the rules. As long as the car meets minimum weight Lipos or sub-c should be legal.
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Old 04-22-2008, 12:19 PM   #583
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Donny,

In your opion compare to a good NMH pack do you think the 5000 Lipo is the better of the two for stock/19t racing?
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Old 04-22-2008, 12:31 PM   #584
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I have been told by a few that they feel the Lipos are as good as NiMh and there are a few who said they are better. The key is to get the car balanced well with the Lipos.
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Old 04-22-2008, 12:49 PM   #585
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Any plans on a saddle packs for 4wd buggies?
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