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Old 11-30-2008, 02:35 AM   #1411
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In all of my experiences I would have to say that Lipo's are about the safest type of battery that RC has ever seen. Assuming that they are handled properly.
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Old 11-30-2008, 08:05 AM   #1412
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Hey Guys,

I heard that Comp. Elec. is now updating their turbo chargers to charge to 8.44 instead of 8.40. It would be interesting to see if they offer that service to those of us who sent it back before that update was offered, and what some of the number differences are, as far as cycling and testing.

Anyway, I direct races at my local track and have decided not to allow heating packs at all. I think 85* will be my cut off. We already check voltage and have had some packs come to tech and fail.

Thanks,
Casey
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Old 11-30-2008, 08:54 AM   #1413
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Adam, First of all hope all is well in Colorado. Secondly I have never heard of Lipo's exploding like the good old NiMH. They just puff smoke and catch fire, right?
If this isn't an explosion,

http://liposack.com/LipoSackv.wmv

I'd hate to see a real explosion. Don't get me wrong, I've seen NiMh cells do just as much damage. I had a 6 cell 4600 go off right on my bench. Basically, it comes down to being careful with the equipment we use. Trying to push the envelope on things like this can spell disaster at the track.
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Old 11-30-2008, 11:37 AM   #1414
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Originally Posted by mojoman View Post
Hey Guys,

I heard that Comp. Elec. is now updating their turbo chargers to charge to 8.44 instead of 8.40. It would be interesting to see if they offer that service to those of us who sent it back before that update was offered, and what some of the number differences are, as far as cycling and testing.

Anyway, I direct races at my local track and have decided not to allow heating packs at all. I think 85* will be my cut off. We already check voltage and have had some packs come to tech and fail.

Thanks,
Casey
The reason why Comp. Elec. is doing this is that many racers were using LRP chargers which you have an option to calibrate the voltage so you can reach 8.44. Going to 8.44 does make the numbers look a bit better. I do have an LRP charger so I can't test the difference but I know it does give a bit better numbers.

Great to hear your not allowing heating of the packs as I think this is just another step that everybody would end up doing and would provide no advantage if everyone does it. Lipos are very easy to handle so we need to keep it this way. What I would reccomend you do is to put a pack in tech as a control pack and allow 10 degrees above the control pack. There could be warmer parts in the building due to pit lights and other things. You warn your racers that if they show up with a pack that is over 10 degrees they don't get to run that run and if it happens again they can't run for the rest of the day.
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Old 11-30-2008, 11:39 AM   #1415
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Originally Posted by SpraydbySprague View Post
If this isn't an explosion,

http://liposack.com/LipoSackv.wmv

I'd hate to see a real explosion. Don't get me wrong, I've seen NiMh cells do just as much damage. I had a 6 cell 4600 go off right on my bench. Basically, it comes down to being careful with the equipment we use. Trying to push the envelope on things like this can spell disaster at the track.

For that to happen you need to overcharge the pack on purpose until it combusts. If a racer is using a Lipo charger that shouldn't happen and this is why you should use a Lipo sack in case of a mistake with the charger setup.
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Old 11-30-2008, 11:44 AM   #1416
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Hey Guys,

I heard that Comp. Elec. is now updating their turbo chargers to charge to 8.44 instead of 8.40
i have one 6months old can i update it?
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Old 11-30-2008, 12:21 PM   #1417
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Originally Posted by brqsdad View Post
Adam, First of all hope all is well in Colorado. Secondly I have never heard of Lipo's exploding like the good old NiMH. They just puff smoke and catch fire, right?
Colorado is great! Hope things are going well out your way.

I'm not an expert on how LiPo's fail, but my understanding is that they are more likely to burn than pop. I've read accounts of small explosions during the burning process, but it doesn't sound as violent as NiMH. I'd still consider someone's pits a few feet from mine going up in flames something to be less than excited about. :-)

More than anything, I just hear a lot of people insist that charging at higher rates is faster on the track (like NiMH) and that appears to be a fallacy. But you can't tell those guys anything, 'cause they're fast!
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Old 11-30-2008, 12:22 PM   #1418
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Originally Posted by mojoman View Post
Hey Guys,

I heard that Comp. Elec. is now updating their turbo chargers to charge to 8.44 instead of 8.40. It would be interesting to see if they offer that service to those of us who sent it back before that update was offered, and what some of the number differences are, as far as cycling and testing.

Anyway, I direct races at my local track and have decided not to allow heating packs at all. I think 85* will be my cut off. We already check voltage and have had some packs come to tech and fail.

Thanks,
Casey
And then there's the guys that leave the voltage clips off and let them charge even higher. Intentional overcharging is dumb.
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Old 11-30-2008, 03:26 PM   #1419
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Colorado is great! Hope things are going well out your way.

I'm not an expert on how LiPo's fail, but my understanding is that they are more likely to burn than pop. I've read accounts of small explosions during the burning process, but it doesn't sound as violent as NiMH. I'd still consider someone's pits a few feet from mine going up in flames something to be less than excited about. :-)

More than anything, I just hear a lot of people insist that charging at higher rates is faster on the track (like NiMH) and that appears to be a fallacy. But you can't tell those guys anything, 'cause they're fast!

Adam-
A couple of the hard-core sedan guys have finally made the switch to LiPo at Fastlane and they are noticeably faster. Not sure what they are doing but the class is about dead because others don't want to do funny stuff to their batteries.

You are correct about LiPo's not exploding. Technically an explosion only occurs when the pressure inside the confinement vessel exceeds the vessels confinement capability and "bursts" the vessel. NiMh cells have a pretty high strength vessel, so when it heats up, material expands and creates pressure. When the weakest point gives you get the explosion as the pressure is vented. Because the lipo does not have a high strength enclosure its explosion potential is not nearly as high.

No, I didn't stay at a holiday inn express last night. In my former job I was an explosion protection specialist and was the company’s representative on the NFPA Explosion Protection Systems Committee.
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Old 11-30-2008, 03:56 PM   #1420
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To keep things equal and fair with Lipos all you have to do is check for overcharging and not allow heating. I assume your track is not doing this ?
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Old 11-30-2008, 04:00 PM   #1421
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Originally Posted by Fastforward View Post
Adam-
A couple of the hard-core sedan guys have finally made the switch to LiPo at Fastlane and they are noticeably faster. Not sure what they are doing but the class is about dead because others don't want to do funny stuff to their batteries.

You are correct about LiPo's not exploding. Technically an explosion only occurs when the pressure inside the confinement vessel exceeds the vessels confinement capability and "bursts" the vessel. NiMh cells have a pretty high strength vessel, so when it heats up, material expands and creates pressure. When the weakest point gives you get the explosion as the pressure is vented. Because the lipo does not have a high strength enclosure its explosion potential is not nearly as high.

No, I didn't stay at a holiday inn express last night. In my former job I was an explosion protection specialist and was the company’s representative on the NFPA Explosion Protection Systems Committee.
Good to hear from yah Bob, thanks for the lesson! :-)
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Old 11-30-2008, 04:27 PM   #1422
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To keep things equal and fair with Lipos all you have to do is check for overcharging and not allow heating. I assume your track is not doing this ?
I would be more than happy to recommend some battery pre race tech inspection if you would like to suggest something. How should this test be performed?

I saw your earlier post that suggested not letting anyone run batteries that are more that 10 degrees F over ambient. How could we check for overcharging?

Thanks
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Old 11-30-2008, 04:33 PM   #1423
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To tech for heating just follow my suggestions as I think it's a fair way to do it.

For overcharging this is done in Tech prior to the run. Just put a voltmeter on the pack and it shouldn't be over 8.44 as this is the allowed margin of error as not all chargers have the same calibration. If a racer has a pack that is above 8.44 he shouldn't be allowed to make his run and you tell him to stop overcharging. Overcharging should never be tolerated and should be considered cheating.
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Old 11-30-2008, 05:08 PM   #1424
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Everyone needs to just charge them at one c and 8.4 volts ..
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Old 11-30-2008, 05:15 PM   #1425
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Please tell me how you can tech to see if a pack was charged at 1C ?
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