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Old 02-18-2008, 07:55 PM   #91
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So what happens on the 3rd, 4th and 5th cycle of these? Does performance go down or can I count on it being the same after cycle 2 and the heat has come up?

How do these compare to the Lipo cells that you have already released? Are these better or the same?
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Old 02-18-2008, 07:57 PM   #92
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The GFX? The best LiPo charger? It's the size of a goddamn VCR, and lacks features of real LiPo chargers! I know this thread is all about being dumb, but can we please draw the line somewhere?
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Old 02-18-2008, 07:59 PM   #93
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The GFX? The best LiPo charger? It's the size of a goddamn VCR, and lacks features of real LiPo chargers! I know this thread is all about being dumb, but can we please draw the line somewhere?
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Old 02-18-2008, 08:19 PM   #94
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Originally Posted by xraysteve View Post
i have a check point charger and a ice both the same. it will only charge at 1c. so if i buy your 4000 pack and tell the charger that it is a 10,000 pack i think it will charge at 10 amps and that is its max. do you see a problem with this.
The BLOODY ICE(checkpoint) Does charge at 2C. The default is 1C but you just need to dial in the amps your looking for. A 3200mah with charge up to 6.4amps and 3600mah up to 7.2amps, set the capacity to 5000mah and you will get 10amp charging for any pack you own.

Discharge in LIPO mode is limited to 10amps but again you need to top up the MAH rating. I dumped a 3600lipo on NIHM mode at 30amp pulse with a 6 volt cut off dialed in, worked fine.
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Old 02-18-2008, 09:01 PM   #95
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Please don't attempt any of the tests I'm performing or use a charge rate higher than 1C. Never warmup your Lipo packs. Doing any of this can result in fire and can be dangerous


If you guys want a high end charger that uses high quality charging and discharging components and can discharge at a true linear 35 amps then the GFX is for you. For all others you can use what you feel works for you but I can assure you the GFX is better charger/discharger. CE has always made the best chargers and it will never change as they use high quality components.

As far as balancing anyone can buy a balancer for 30-45 dollars.

Now on to the ones who think a high charge rate makes no difference please tell me the tests you have done ?

Here are my test results on this that proves what I'm saying:

Pack 1 charged at 5 amps: 499-7.16-12.9
Pack 1 charged at 12 amps: 500-7.20-11.2

Pack 2 charged at 5: 507-7.14-13.0
Pack 2 charged at 12: 505-7.20-11.5

I have done this test atleast 4 times with 12 amps always being the best method to get higher average voltage and lower IR.

My next test is to try warming up the pack at 140-150 degrees and then charging and discharging it to see if it gives the same result as back to back charging discharging.

Last edited by Danny/SMC; 02-19-2008 at 11:32 AM.
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Old 02-19-2008, 12:38 AM   #96
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Please don't attempt any of the tests I'm performing or use a charge rate higher than 1C. Never warmup your Lipo packs. Doing any of this can result in fire and can be dangerous

I have good/bad news to report.

Good News: Those who have mentioned the reason why discharging a pack at 35 amps and then charging it back up was due to the heat build up were correct.

Bad news: So far in my early testing I have tried two different temperatures and the hottest one provided the best result. I will be testing this some more but this may make things even more complicated than I originally thought. The temperature after a pack has been cycled is 140 or so. I put the same pack in the oven for 1 hour to make sure it got the temp up internally. After 1 hour I took it out and immediatley started a cycle. The pack temp when it came out of the oven was 183.

Test: I cycled a pack then cycled it immediately after the first cycle was done. The pack temperature was 141 after the first cycle was over. I then let it cool down. I then placed the pack in the oven for 1 hour and thencycled it as soon as I pulled it out of the oven and the temp was 183.

All cycles are done with a 12 amp charge and a 35 amp discharge.

Results:

Cycle 1: 497-7.20-11.5

Cycle 2 started immediately after cycle 1 : 500-7.25-10.0

Cycle 3 started immediately after pack was out of the oven: 500-7.28-9.0


So it seems like getting the pack up in temp by 40 degrees has dropped the IR by 1 milliohm and increased the average voltage by .03

Now I need to test a higher temp to see if it will provide better results. At 183 the pack was getting kind of hot to handle and I'm not sure what kind of device we can bring at the track that will get these temps. I will be getting a new discharger that will do 100 amps so I will see if this will get the temperature to be at 180 or higher.

So for the guy who mentioned that 40 degrees celsius was the optimum temp for Lipos I think your info is incorrect as 183F is 84C and maybe higher than 183 will give better results.

Last edited by Danny/SMC; 02-19-2008 at 11:31 AM.
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Old 02-19-2008, 01:44 AM   #97
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It'll be interesting to see what you find at 190+.

Quote:
Originally Posted by linger
Ideally you want the ending battery temp below 150 deg F so you can start out around 100-110 deg F. Once you hit about 190 deg F, the battery electrolyte starts breaking down and you will be massivley reduced preformance. One you hit about 390-400 deg F (depends on exact chemistry) - you will have a fire.
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Old 02-19-2008, 03:14 AM   #98
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This would be a better test if you could knock out a batch of cookies, or pizza bites at the same time.
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Old 02-19-2008, 03:14 AM   #99
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It's the size of a goddamn VCR
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Old 02-19-2008, 03:40 AM   #100
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Danny, thanks for posting your side of the discharge data providing temperatures info from your GFX before and after each cycle. The temp info wasn't there on the data's you provided previously. I have found similar results on my side here by increasing temps on each cycle in observing drop in IR'#, and increase in Vlt each time. It does make a difference and helps to puts things in perspective, when you add the temperature part to the overall discharge data.

I would think though, that warming up a Lipo pack to a user set "x" temperature through a warmer or other means, and re-activating the chemistry of the Lipo pack through a couple of practice session (or few partial discharges on the bench) should be sufficient to get best results on the track during race day.

Depends on what a racer is looking for though for the class they’re running in though. I think the rest of it, however can come from choosing ideal lower turn motor/gearing combo, than taking the Lipo's to extreme temp (past the ideal optimal temp) to achieve best performance though. But it's good to see what you come up with, as I haven't tested at those temps or more. I'll leave that to you, lol.
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Old 02-19-2008, 06:39 AM   #101
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Quote:
Originally Posted by Danny/SMC View Post
The GFX is the best discharger/charger. I will measure the temp of the leads when a pack is on discharge to see what they are at. It's normal for the leads to get warm at 30/35 amps.

I'm sure if you were to use another device at 30/35 amps you would get the same temp in the leads.
I realize these are not "buildings" but in the NEC..when you hit the 30A rating, buildings are supposed to be using 10ga. wire vs. 12. I have a distribution box I built using 12..and the leads were getting hot when myself and my pit partner were using all our equipment at the same time. I re-wired the box using 10ga... problem solved. Just fyi.
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Old 02-19-2008, 06:40 AM   #102
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Originally Posted by Danny/SMC View Post
So for the guy who mentioned that 40 degrees celsius was the optimum temp for Lipos I think your info is incorrect as 183F is 84C and maybe higher than 183 will give better results.
Good information.

Personally, I will never attempt to manually heat a battery to 183F. I might warm them up in a heating pad when it's cold, below 60F at the track, otherwise, thanks, but no thanks.

I guess once top-level racers start using LiPo's at the national races in place of NiMh, this information could come in handy.
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Old 02-19-2008, 06:45 AM   #103
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Danny,

Is discharging still required after every run, or is that just a method of increasing the internal temp of the pack? Your testing seems to be fairly consistent with results, would you be able to charge a pack, then run it for 5 minutes, then just repeak and check the discharge numbers after that?
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Old 02-19-2008, 07:26 AM   #104
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Originally Posted by Danny/SMC View Post
I just measured wire temperatures after a 35 amp cycle and I'm getting 105-110 farenheit. If your wires got hotter than this then I suspect a bad connection which would increase resistance and create more heat.
Thanks for checking into that Danny.
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Old 02-19-2008, 07:56 AM   #105
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Danny, could you post some avg laptimes based on your charging methods and vs other packs on back to back runs? Unfortunately my charging #'s dont win me prizes Id like to see how your packs can help me on the track.
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