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Old 11-08-2007, 06:59 AM   #1
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Default "Lipo vs. NiMh" - end of the safety discussion

http://www.redrc.net/2007/11/norwegi...all-ep-racing/

Sorry to hear that for our norwegian friends... but glad to see a factual piece of news that proves that Lipo's aren't any more dangerous than sub-C's, as long as used properly.

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Old 11-08-2007, 07:50 AM   #2
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This was a national event. I'm surprised only 3 incidents occurred. People are intentionally charging at high amps to get all they can out of the cells. At the Worlds a few years back (and it probably still happens), guys would run a pack 6 times and toss it because it was all used up. At the OffRoad Worlds in Japan this year there were similar exploding incidents. Similar issues happen at the OnRoad worlds in Italy. "we're burning up speedos and motors and yadda" .. guess where much of that heat comes from?? When you pull your batteries off the charger and they're venting, then toss it into a car the heat attempts to dissipate through the wires to whatever is connected. (Brushless guys recognize this well as they have to gear by it or dread the overheat sensor cutting off the power.) Then run a 5 minute race balls to the walls praying that the everything stays soldered together. Its amazing that most of the cars come off the track in one piece after what these guys can put them through.

There's no doubt that there are safety concerns with both chemistries.. some guys are afraid of explosions(nicd/nimh), some guys are afraid of fires.(lipo) - anyone dealing with either of these situations such as a firefighter or explosive ordinance person will tell you its much easier to contain a relatively small fire than an explosion.

But no matter what power source we're using..
It does not matter what we race with when people abuse the equipment.
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Old 11-08-2007, 08:40 AM   #3
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The thing is, are people just charging their batteries higher than in the past, or are the latest cells not up to task? Haven't people always abused batteries at national events? Not saying it's right, but what's changed recently causing so many incidents? Most fingers seem pointed at the batteries themselves.

It's a shame people feel they have to abuse their batteries to gain that extra edge, but clearly that's how it's going to be at every big race, and we can't expect it will stop on its own. Can such abuse be quelled by implementing rules forbidding certain behaviors? What about spec batteries? Maybe mandatory charging bunkers for NiMH and LiPo? Halting EP racing doesn't seem like a good option.
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Old 11-08-2007, 08:55 AM   #4
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Its the quest for max power and guys pushing the limits of the cells.
At a recent national i saw guys pumping IB and EP 4200 batts at 8 and 10amps when the norm is 5-6 amps.
Something is bound to happen sooner or later.
After reading a few posts in the last week i went and bought safety glasses yesterday to wear at my workbench and at the track.

Lipo was a issue but havent heard and seen any problems with them of late especially not as bad as with the nimh batts.
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Old 11-08-2007, 08:58 AM   #5
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My opinion, they are both dangerous if handled improperly, or abused. But can also both be safe if handled correctly and the way they were designed to be.
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Old 11-08-2007, 09:15 AM   #6
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Never forget that the change for 5 cells, and the use of unlimited motors, (with 5 or 6 cells) have made the problem of the batteries worst.

People say that the change for 5 cells was because the car were going to fast. In fact what happened was that the ESC of a known brand could not hold the power and put a lot of problems to everybody with six cells. As you know there are other ESC that can hold with a lot more cells with no problem.

i have always said here were i live that going with 5 cells does not mean that the cars will be slower. If you change to another motor with less turns at the end you will be with the some power but at the cost of more Amps from the cells. Simply, power = volts x amps. So you see with less volts you can have the some power if you rise the amps.

With the rise of the amps at the batteries two things happen, you will have less time to drive and the batteries will be hotter. NiMh cells are known to develop a bigger internal resistence as they are abbused. The more power you ask out of them the more IR you will have. At the end they will not work.

Remenber the guys in Electric pylon racing planes that use the some NiMh batteries 1 (one) time. After that they are useless because of so high rate discharge.

So, all the rules seems to go the opposite way they should go to make this hobby a better hobby, but they are the clever guys they know better
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Old 11-08-2007, 09:37 AM   #7
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Default some thoughts

What are the battery matchers going to do in norway? How will they make money? Isn't supporting the battery matching business more important than safety? Come on people, show the love.

R/C is more important than safety. How will guys feel good about themselves in their hobby if they can't race r/c cars?

This is another nail in the coffin of nimh for r/c cars. It is only a matter of time.
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Old 11-08-2007, 09:42 AM   #8
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Quote:
Originally Posted by syndr0me View Post
It's a shame people feel they have to abuse their batteries to gain that extra edge, but clearly that's how it's going to be at every big race, and we can't expect it will stop on its own. Can such abuse be quelled by implementing rules forbidding certain behaviors?
the thing is, most of the top guys that i know of charge at 6 or 7 amps (brad johnson, jim herrmann, ea, drew ellis, etc). we've all missed our charge points from time to time and had to bump it up in order to peak, but there is nothing to gain from charging our current cells at high current rates. i think that's old school stuff, and frankly, it shouldn't be a real concern. if you get to a big race, look at everyone's chargers (in particular the fast guys). you'll see alot of 6-8amp charge currents being displayed. there are always some jokers out there that are just doing things wrong (remember - national race does not mean all the racers have that kind of talent or brains). frankly, i don't feel that competition is the problem here. we weren't blowing up gp's (with higher delta numbers, no less).

the problem is that there's nothing written up in the approval process (to my knowledge) that requires any substantial durability/longevity data prior to approval. of course matchers are going to sell disposable cells if they are faster. and of course, racers (who can afford it) are going to be running them. you'd be a tame competitor if you didn't do either. we need a bigger effort from a third party to require more stringent criteria to be met prior to new cells being approved for racing. you can't leave it up to either the matcher or the racer to budget safety with competitiveness.

long story short, the cells are the problem. you can't keep cramming more and more into the same envelope and expecting every parameter to go in the positive direction. someone needs to mandate that development takes place on the durability side of things (and be proven), if only by setting voltage and capacity limitations well under what is theoretically achievable. it doesn’t matter what technology you are using, if you fail to impose a limitation on performance, or to prioritize safety, over time it will all gravitate that way. having apparently put nothing in place to curtail this downward spiral, the norwegian federation is left with nothing but a kneejerk reaction, which was to simply stop. nice, eh? a "time out" if you will. a proud moment for all involved.

pdm - dead on.
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Old 11-08-2007, 09:46 AM   #9
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Quote:
Originally Posted by seaball View Post
the thing is, most of the top guys that i know of charge at 6 or 7 amps (brad johnson, jim herrmann, ea, drew ellis, etc). we've all missed our charge points from time to time and had to bump it up in order to peak, but there is nothing to gain from charging our current cells at high current rates. i think that's old school stuff, and frankly, it shouldn't be a real concern. if you get to a big race, look at everyone's chargers (in particular the fast guys). you'll see alot of 6-8amp charge currents being displayed. there are always some jokers out there that are just doing things wrong (remember - national race does not mean all the racers have that kind of talent or brains). frankly, i don't feel that competition is the problem here. we weren't blowing up gp's (with higher delta numbers, no less).

the problem is that there's nothing written up in the approval process (to my knowledge) that requires any substantial durability/longevity data prior to approval. of course matchers are going to sell disposable cells if they are faster. and of course, racers (who can afford it) are going to be running them. you'd be a tame competitor if you didn't do either. we need a bigger effort from a third party to require more stringent criteria to be met prior to new cells being approved for racing. you can't leave it up to either the matcher or the racer to budget safety with competitiveness.

long story short, the cells are the problem. you can't keep cramming more and more into the same envelope and expecting every parameter to go in the positive direction. someone needs to mandate that development takes place on the durability side of things (and be proven), if only by setting voltage and capacity limitations well under what is theoretically achievable. it doesn’t matter what technology you are using, if you fail to impose a limitation on performance, or to prioritize safety, over time it will all gravitate that way. having apparently put nothing in place to curtail this downward spiral, the norwegian federation is left with nothing but a kneejerk reaction, which was to simply stop. nice, eh? a "time out" if you will. a proud moment for all involved.

pdm - dead on.
I couldn't agree more!
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Old 11-08-2007, 09:46 AM   #10
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I will never, ever buy a Nk-Ml pack again....

Roar ?

Seems they still think they are safe though .....
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Old 11-08-2007, 09:54 AM   #11
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So who's going to be first to market with an explosion proof charging sock for NiMh packs?

The biggest risk is for the people in the pits within 20' of the person being foolish - they're the ones least expecting a cell to pop and hot shrapnel to go flying about.
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Old 11-08-2007, 10:01 AM   #12
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Quote:
Originally Posted by Wild Cherry View Post
I will never, ever buy a Nk-Ml pack again....

Roar ?

Seems they still think they are safe though .....
You know ROAR is stupid people.
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Old 11-08-2007, 10:06 AM   #13
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seaball,

Very insightful, thank you. I can only glean certain things from posts on here since I haven't made my way to big events just yet.

For the rest of you, there's no reason to try and bend this into a way to promote LiPo. Even if our choice of battery is different, we're all EP racers, and should view this as a deeply troubling development. Anyway, LiPo in racing will face the same challenges as soon as people realize you can get more voltage by overcharging them (true), even if it's highly dangerous and extremely detrimental to the cell's life. Be careful what you wish for.
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Old 11-08-2007, 10:14 AM   #14
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Quote:
Originally Posted by syndr0me View Post
seaball,

Very insightful, thank you. I can only glean certain things from posts on here since I haven't made my way to big events just yet.

For the rest of you, there's no reason to try and bend this into a way to promote LiPo. Even if our choice of battery is different, we're all EP racers, and should view this as a deeply troubling development. Anyway, LiPo in racing will face the same challenges as soon as people realize you can get more voltage by overcharging them (true), even if it's highly dangerous and extremely detrimental to the cell's life. Be careful what you wish for.
Wish ?

I know which battery is the safest for racing now ....


The Nk-Ml company's have shot themselves in the foot and doubt they will be able to walk away from this one ...
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Old 11-08-2007, 10:26 AM   #15
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Sindrome the only way that one can overcharge a lipo is selecting 3 cells instead of 2 in the charger isn't it?

Hardly anything diferent will happen that after that charge that people will put that batterie in the recycle bin. Ok, if that one is pacient enought he can wait until the cell gets fire, but that is not 100% sure because some of them will not get on fire...so.

If you put problem against problem I believe that the majority of us will prefer to have a cell on fire close to us, that you can notice and avoid, than a explosoin throwing metalic pieces all over the place that no one will know how to avoid.

Am I thinking wright?
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