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Old 06-19-2008, 02:26 PM   #46
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Syndrome....thanks for the links I will look all that over. Yeah I donít think itís a safety issue as much as it is a longevity issue. But with new lipos out all the time for me I would be more inclined to get a new pack before the life of my old ones are up....so I might never see the effects if there are any from higher rate charges. For me the whole higher amperage is all about time getting it done sooner.
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Old 06-19-2008, 02:36 PM   #47
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I'll be the first to admit I have a short amount of experience with LiPos. I have been charging my 4000 pack at 6 amps, which is 1.5C, with great results. I wonder if this is a more balanced way to get some performance/faster charging w/o sacrificing too much longevity.
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Old 06-19-2008, 04:17 PM   #48
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I suppose the only thing to consider with longevity is that if graphs are to be believed, you start seeing a reduction in capacity fairly quickly. I imagine reduced capacity will affect the discharge curve, which is probably a bad thing in the eyes of most racers.

Anyway, there doesn't seem to be a real definitive answer on the subject. I guess time will tell if it matters, and how much.

I'm just glad to see you suckers finally joined me on the bandwagon. :-)
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Old 06-19-2008, 06:05 PM   #49
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I must just be missing something, IF one battery can last all the heats and the main, what is the hurry in getting the battery charged. If you have 2 batteries you should be very good for one night of racing for one car easy.

I always charged my nicads,nimh at VERY low rates, sure they did not have the punch but they did seem to be stronger longer.

Lipo is very intresting in that two batts can get you by on a night of racing and practice easy.

Any thoughts on the two packs that I bought Trinity 4500 with the internal voltage cutoff, and the Reedy 5000.

Also could anyone point me in a direction or give advise on if there is any gearing changes I need to do. I have not changed to brushless yet so these will be used on 27T motors.

Thanks
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Old 06-20-2008, 02:15 AM   #50
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What concerns me most of all about charging over 1C is the buildup of crystals in the cells. Unless there are packs that handle a 2+C charge rate under all circumstances, I will stick with the 1C rule of thumb. The safety of myself and others always takes priority over fast charging.

Also, I'd much rather have them last the stated length of time instead of having to replace them annually.
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Old 06-20-2008, 04:48 AM   #51
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1 pack and charge at 1.5c between races. I've been doing this for 2 years. Had one pack last year and got a new one this year but the old pack is still very good.
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Old 06-20-2008, 06:18 AM   #52
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Quote:
Originally Posted by syndr0me View Post
Linger has made a number of posts on the subject here on RCTech, including graphs with hard data. Whether or not you trust his expertise is entirely up to you, but ROAR trusts him enough to be their resident expert. You can find some good discussion on the topic here and here, with related graphs.
I would have no problem accepting Linger's graphs if he actually showed data on cells that are the correct size. A 2 cell 3200 pack is two 3200 mah cells in series. There's a rather significant difference between a little 750 mAh cell and a 3200 mAh cell. Apples and oranges just like if we compare a AA NiMh to a sub C NiMh. Linger is pretty smart and he should know that we should compare apples to apples.

I will say that to charge anything over 1C you should be using a balance charger. Personally, I think that balancing should only be done during charge.

I know that quality packs like Orion and SMC won't get hot with a 10 amp charge on a good charger. If your cells are getting hot at 1.5 or 2 C they're probably not very good cells or your charger is overcharging...
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Old 06-20-2008, 06:44 AM   #53
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Have you looked at what they say about NIMH cells they should be slow charged at 1amp right on the cells.....yet I dont know anyone who charges them at 1 amp. Do you think the amperage was blowing up NIMH cells or was it the crappy cells that were blowing up?
I do, but I guess it's those that wanted their nimhs to last months instead of weeks. Considering how few sources are out there for batteries I'd still be willing to bet it was capactity and charge rate related.

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Syndrome....thanks for the links I will look all that over. Yeah I don’t think it’s a safety issue as much as it is a longevity issue. But with new lipos out all the time for me I would be more inclined to get a new pack before the life of my old ones are up....so I might never see the effects if there are any from higher rate charges. For me the whole higher amperage is all about time getting it done sooner.
I'll just say that while I've been running LiPOs for about 4 years now with no problems, I have seen and heard all sorts of horror stories about them from just croaking to puffing up to catching on fire and seemingly all from people that have charged at a high rate.
But the fact that some of you are in such a hurry and don't mind replacing packs hardly seems reason or justification for telling others it's OK.
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Old 06-20-2008, 07:03 AM   #54
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But the fact that some of you are in such a hurry and don't mind replacing packs hardly seems reason or justification for telling others it's OK.
Should we lie to keep you happy?

The scorpion system was charging kokams at 3c 4 years ago.

Maybe the bottom line is the quality of the charger + pack, if you have a good balance charger you can run a single pack all day, reduces startup cost and things to carry to the track. You can also leave a pack taped in your car all day.

Charging cells warm is better for them so that can offset the higher amp rate.
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Old 06-20-2008, 07:06 AM   #55
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Speaking of apples and oranges what about 2 cell 7.4 and 4 cell 7.4 balance charging at more then 1c ???? I think it might be OK for 2c but maybe not for 4c 7.4's.
My 4 cell 7.4 lipo did not like discharge balancing at all but my 2 cell is still fine.
I'll never buy another 4 cell 7.4 thats for sure and I will never discharge balance again.
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Old 06-20-2008, 07:10 AM   #56
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Originally Posted by RocketRob40 View Post
But the fact that some of you are in such a hurry and don't mind replacing packs hardly seems reason or justification for telling others it's OK.
Quote:
Originally Posted by JevUK View Post
Should we lie to keep you happy?
No, but neither is using the "I don't care how quick my packs wear out" excuse as a justification to go against manufacuturer's recommendations.
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Old 06-20-2008, 07:16 AM   #57
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Originally Posted by JevUK View Post
Maybe the bottom line is the quality of the charger + pack, if you have a good balance charger you can run a single pack all day, reduces startup cost and things to carry to the track.
I don't know for sure of any particular user issues with quality chargers, since most of the ones I'm aware of or am using are quality units. But then again, some manufacturers warn against the whole balancing thing anyway.

http://www.pfmdistribution.com/
"For years we have sat quietly aside watching the proponents of "pack balancing" spew forth misinformation. The truth is that a properly matched pack will not require balancing. Yes, we're sure this is a shock to many of you who have fallen for the balancing gimmick. Yes, Apogee was the first to put commercial grade plugs on all packs due to customer demand. We've had and seen enough.

Pack balancing is a gimmick perpetuated by companies who make balancers, and by other companies who do not match battery cells within the pack."




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You can also leave a pack taped in your car all day.
Watched two people in the last year burn down their cars that way, so that seems pretty foolish as well.
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Old 06-20-2008, 07:26 AM   #58
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Quote:
Originally Posted by RocketRob40 View Post
I don't know for sure of any particular user issues with quality chargers, since most of the ones I'm aware of or am using are quality units. But then again, some manufacturers warn against the whole balancing thing anyway.

http://www.pfmdistribution.com/
"For years we have sat quietly aside watching the proponents of "pack balancing" spew forth misinformation. The truth is that a properly matched pack will not require balancing. Yes, we're sure this is a shock to many of you who have fallen for the balancing gimmick. Yes, Apogee was the first to put commercial grade plugs on all packs due to customer demand. We've had and seen enough.

Pack balancing is a gimmick perpetuated by companies who make balancers, and by other companies who do not match battery cells within the pack."






Watched two people in the last year burn down their cars that way, so that seems pretty foolish as well.
What their pack magicaly caught fire because it was in a car? I smell BS.

Balance charging is not a gimmick, it only takes a small amount of logical thinking to understand why.

If one cell becomes discharge lower than the other, the higher charged cell will subsequently be overcharge and start to puff.

Oh and PFM are crooks..
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Old 06-20-2008, 07:54 AM   #59
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Quote:
Originally Posted by RocketRob40 View Post
I'll just say that while I've been running LiPOs for about 4 years now with no problems, I have seen and heard all sorts of horror stories about them from just croaking to puffing up to catching on fire and seemingly all from people that have charged at a high rate.
But the fact that some of you are in such a hurry and don't mind replacing packs hardly seems reason or justification for telling others it's OK.
I have seen more lipo's blow up or puff up charged at lower rates(less than 1C) then higher rates(over 1C). So following your logic it seems that higher rates are safer to me. Thatís not the point some cells lipo or Nimh will be bad and malfunction periodÖ.most times its user error. I have never had a pack of Nimh cells or a lipo explode or anythingÖ.I guess Im just lucky or Im cautious by making sure everything is proper before chargingÖIm going with the latter because you make your own luck when its something you have control over.

Here is the thing I donít understand Lipo was going to be the great savior and you would only need 1 pack for racing all day. Yet I still see people with 4 or 5 lipo packs.....it doesnít make any sense to me. Right now I have 1 lipo pack that I use all day 6 or 8 charges a day. And you know what by the end of the day the thing is faster then when I started the day. So I have 1 100 dollar lipo pack and not 4 or 5 100 dollar lipo packs so when this one pack starts to show any signs of slowing down I will just go buy another pack and repeat the process all over again. And guess what at the end of 2 or 3 years Im sure I will have spent less money then someone who has 4 or 5 packs and charges at 1C.

And to the guy that said the pack should last multiple races on 1 charge I can tell you that a fully charged lipo is faster then 1 that has been run for 5 or 6 minutesÖ.yes it can be done but you will sacrifice power.
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Old 06-20-2008, 07:58 AM   #60
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You can also leave a pack taped in your car all day.
That may be ok in the UK, ROAR rules specifically state Lipos need to be charged in a sack.
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