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Old 09-16-2007, 11:21 AM   #16
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Take any sub-C cell, any old cell. Make sure its completely discharged. Cut it in half 90 to the +/- axis. I used a scroll saw with a 1/16th blade.

You will be able to see between the "plate". There isn't much room for "heat or bump expansion" in these batts.

A picture is worth a thousand words - if possible compare between 2000 and 4200.
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Old 09-16-2007, 12:41 PM   #17
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I worry about what'll happen when one of these things knocks a 10yr olds eye out. Not good.

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Old 09-16-2007, 03:36 PM   #18
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Default nimh dangers

Wait a second. Nimh batteries are safer and cheaper than lipo. Just because there has been an increase in the number of nimh exploding over the past year, it can't be the cells that are getting more fragile. It must be the chargers. It might also be the lipo cells coming alive and changing the charger settings to rid the world of nimh cells.

The truth seems to be that this is just another characteristic of the new generation of nimh cells. For several reasons, the new cells are more prone to being overcharged.
1) as the cells increase in capacity, charging amps is also increasing. Anytime you increase the amps, if the charger doesn't catch the peak, the cells will get hotter faster and then boom.
2) how many people routinely use temp cutoff in charging. Temp cutoff is designed to prevent over charging. You can set the cutoff at 130 degrees if you want, and that should prevent the cells from exploding.
3) the self discharge curve of the cells and their erratic voltage is playing havoc with the peak charging circuits- if you are charging 6 cells in a pack, and one cell has charged while the others are still charging, you will probably not pickup that cell's peak. If the cell peaks are far enough apart in time, 1 cell could overcharge and blow.

Whenever you push technology, as in stuffing more capacity into the same space, you change some of the characteristics of the cells. In the new generation of cells, that change is simply a more fragile cell that cannot handle overcharging.

It's interesting that this discussion mirrors the progression of the LIPO cell discussion. The cells blow, the culprit is always the user. However, charging LIPO is different from charging nimh. For 1 thing, there is no peak or temp cutoff. For another, most charge lipo at 1c. So far, on rctech anyway, there have been many reports of nimh blowing up, but none of an orion lipo blowing up. Considering orion uses kokam cells in a plastic case, and all of the nimh are either IB or EP, a comparison of the lipo vs nimh cell's safety is applicable.

When LIPO first came out for the rc market, the doom and gloom and warnings of fires were everywhere. Now it seems that the doom and gloom has shifted to the nimh batteries.

The conclusions are obvious and apparent. I just wonder when the "r/c" industry will get it, and at least approve LIPO's for competition (ROAR?)

Last edited by billjacobs; 09-16-2007 at 04:04 PM.
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Old 09-16-2007, 03:51 PM   #19
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I've seen dozens of wrecked Civics driven by people who had no idea what they were doing, or they pushed the car too hard, does this mean I can start a "The danger of Honda Civics" thread. What about BBQ grills? the whole premise of a grill is based around FIRE!!! Many race tracks grill Hot Dogs to serve to their patrons, where's ROAR's concern over this ridiculously unregulated safety issue? Dear God, we better get the sanctioning body involved to put a stop to this insanity.
Gimme a break........
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Old 09-16-2007, 04:00 PM   #20
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Just like in machining...run it until it breaks, then back it down 5%...that's the sweet spot.

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Old 09-16-2007, 04:07 PM   #21
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this thread is simply a response to the LIPO bashing threads. No one is advocating that ROAR ban nimh. But if the point is that ROAR shouldn't be the babysitter and ban products from competition, why aren't LIPO approved?
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Old 09-16-2007, 04:12 PM   #22
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Craps- are you kidding me? This was the one good chance you've been waiting for to come into the limelight to push lipo over nimh. You seem to think lipo's are the greatest wave of safety. Where are you racing next week, I am sure I can blow a lipo up in your face if you want. By now we all know lipos are becoming more and more popular, this isn't 2 years ago where you had to spam every message board with your sales pitch. Let it rest .
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Old 09-16-2007, 04:16 PM   #23
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At the two regional events I've attended this year at least one NIMH pack has blown up. They both just happen to be Intellect Battery 4200's.

I'm guessing these are made in China. With all the problems Chinese products have caused these days it will cause a trickle effect in all industries to force companies to test more extensively (more quality control) and government regulations become more strict. And in the end they'll just stick a bigger price tag on the battery for all the testing time.

The funny thing is I've been racing on and off since 1986. I never once saw a Panasonic or Sanyo battery blow up. It's only with these new companies that I've seen batteries blow up. Even when the buzz boxes were in style (boxes that peak batteries at like 20amps just before you race) in oval racing in the late 80's never saw or heard of batteries blowing up.

Last edited by Apex; 09-16-2007 at 08:03 PM.
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Old 09-16-2007, 04:18 PM   #24
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Do lipos actually blow up or do they flame up?

I know NIMH's blow up and are probably about as powerful as an M80. NIMH's are like little grenades since the metal pieces apart like shrapnel.
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Old 09-16-2007, 04:20 PM   #25
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Maybe thats why Dale jr missed the chase this year.. To many blown engines.. Just a racing thing ya wana go fast.. Some of the fast stuff may pop at any time class or sport!! Ya wana go slower buy the other stuff and when a fast racers shows ya get beat..LOL
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Old 09-16-2007, 04:50 PM   #26
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Quote:
Originally Posted by sportpak View Post
I worry about what'll happen when one of these things knocks a 10yr olds eye out. Not good.

Ben
This should be the concern since so many newbies use nickel batteries!

Quote:
Originally Posted by billjacobs View Post
Wait a second. Nimh batteries are safer and cheaper than lipo. Just because there has been an increase in the number of nimh exploding over the past year, it can't be the cells that are getting more fragile. It must be the chargers. It might also be the lipo cells coming alive and changing the charger settings to rid the world of nimh cells.

The truth seems to be that this is just another characteristic of the new generation of nimh cells. For several reasons, the new cells are more prone to being overcharged.
1) as the cells increase in capacity, charging amps is also increasing. Anytime you increase the amps, if the charger doesn't catch the peak, the cells will get hotter faster and then boom.
2) how many people routinely use temp cutoff in charging. Temp cutoff is designed to prevent over charging. You can set the cutoff at 130 degrees if you want, and that should prevent the cells from exploding.
3) the self discharge curve of the cells and their erratic voltage is playing havoc with the peak charging circuits- if you are charging 6 cells in a pack, and one cell has charged while the others are still charging, you will probably not pickup that cell's peak. If the cell peaks are far enough apart in time, 1 cell could overcharge and blow.

Whenever you push technology, as in stuffing more capacity into the same space, you change some of the characteristics of the cells. In the new generation of cells, that change is simply a more fragile cell that cannot handle overcharging.

It's interesting that this discussion mirrors the progression of the LIPO cell discussion. The cells blow, the culprit is always the user. However, charging LIPO is different from charging nimh. For 1 thing, there is no peak or temp cutoff. For another, most charge lipo at 1c. So far, on rctech anyway, there have been many reports of nimh blowing up, but none of an orion lipo blowing up. Considering orion uses kokam cells in a plastic case, and all of the nimh are either IB or EP, a comparison of the lipo vs nimh cell's safety is applicable.

When LIPO first came out for the rc market, the doom and gloom and warnings of fires were everywhere. Now it seems that the doom and gloom has shifted to the nimh batteries.

The conclusions are obvious and apparent. I just wonder when the "r/c" industry will get it, and at least approve LIPO's for competition (ROAR?)
Good post!
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Old 09-16-2007, 06:29 PM   #27
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Quote:
Originally Posted by billjacobs View Post
this thread is simply a response to the LIPO bashing threads. No one is advocating that ROAR ban nimh. But if the point is that ROAR shouldn't be the babysitter and ban products from competition, why aren't LIPO approved?
Yes yes and yes.

Quote:
Originally Posted by Brandon Melton View Post
Craps- are you kidding me? This was the one good chance you've been waiting for to come into the limelight to push lipo over nimh. You seem to think lipo's are the greatest wave of safety. Where are you racing next week, I am sure I can blow a lipo up in your face if you want. By now we all know lipos are becoming more and more popular, this isn't 2 years ago where you had to spam every message board with your sales pitch. Let it rest .
I have been the poster child for lipo, an advocate for their superiority in safety over nimh and this "wave" of sub c's exploding solidifies my stance. Glad no one gets hurt, but ROAR might have some problems on their hands when it comes time to revise the rules.
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Old 09-16-2007, 07:30 PM   #28
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These kinds of posts, threads, articles, blog entries, and so on in other industries are referred to as intentionally spreading FUD: fear, uncertainty, and doubt.

Fear because the intent is to scare people.

Uncertainty because the target audience is assumed to have relatively limited knowledge about the inner machinations of the subject, and thus are assumed to be highly susceptible to this type of propaganda.

Doubt because the ultimate goal is to get the consumer to doubt the product.

In other words, it's not much different than information terrorism. To get people all riled up and fearful about technology.
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Old 09-16-2007, 07:56 PM   #29
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not only this IS fud indeed but also, bear in mind that:

- at most races, you will see people charge at 7 or even 9amps those 4200hence no wonder you re exposing yourself to more potential issues than at 5.5
- 1700s charged at 4amps used to blow up too
- 2 occurrences are not considered as "a rash" especially considering how competitive the race is, and how much some will push those packs..
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Old 09-16-2007, 07:59 PM   #30
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it must've been a female cell to blow a head gasket that bad...

seriously though, following proper instructions will result in safe operation. people go Waaa and say a certian bat type should be banned when they abuse it. if you are doing things you arent supposed to be doing, then dont cry when things explode!

if you follow common sense, and the rules, you'll be safe. pure and simple. its when you abuse things accidentally or intentionally that things go wrong.
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