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Old 03-21-2007, 04:57 PM   #166
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We had two cells in a guy's NIMH pack blow up about 3 weeks ago, two explosions around 30-45 seconds apart. It honestly sounded like a gun blast. He wanted them out of the building, but who in their right mind would pick them up without a face mask on. I have no doubt they could have caused serious eye damage to anyone who took an end cap in the face. He was charging them at the time, and was a very experienced racer. I have no information as to what exactly went wrong, the charger or ???? So for me, its more than just rumours that nimh cells can do more than just vent.
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Old 03-21-2007, 07:07 PM   #167
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When I posted a few pages back about LiPoly, I also should have stated that these new IB cells are also just as dangerous if not more since people have become acustomed to the SAFE factor of the previous GP3300's. I have yet to buy an IB3800 or IB4200 for this reason. My IB3600's seems fine but I always am aware of where my face is in relation to the packs. NiMH cells do internally short and when you push the envelope to gain more energy, the insulators become thinner and more susceptable to contaminants and punchures during manual assembly in the factory.

It seems based on some of the responses that there are better/safer LiPOly cells out there. Its a provn fact, if a product line uses Lithium based cells/packs, you will see an incident. Just beware before making jokes. It sure looks like that IB cell was shrapnel.
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Old 03-22-2007, 09:13 AM   #168
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Correct me if I'm wrong, but...

Nimh cells have vents built into the positive side of the cell. If for some reason the internal pressure builds up the gases are vented through these. I'm sure you've heard the term the cell vented, meaning they heard a small hiss coming from the cell. What happens over time the vents get clogged from dirt, solder, flux and the excess pressure has no where to go until the strength of the cell cap is exceeded, usually with a loud bang.

In other words no matter what you use you need to be careful with this stuff.
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Old 03-22-2007, 10:33 AM   #169
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Hi Jiml

Actually you are correct that cells have built-in vents, however, the vents can become clogged due to manufacturing defects also. I am not aware if the cells that we have talked about here had the vents blocked due to external contamination. Basically, when a cell has a blocked internal vent, the internal short circuit builds up heat and pressure and has no where to go and therefore the cell now acts like a rocket propulsion system. If an external contamination blocks the cell, its possible that it would not cause the jelly roll to be exposed from within the cell.

Most of the time, NiMH incidents are due to internal short circuits. These cells when internally shorted may not "explode" but can and will become very very hot up to 200F and more. I am not a chemist but the black soot is one of the chemicals used to create the energy and I would not want to ingest this either.
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Old 03-22-2007, 12:15 PM   #170
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There are some distinct advantages with lipo's. All of which have been mentioned in this threa. I use them on my planes and heli's all the time. And yes, Or8tal, we do charge them in the same pit area. However, in general, the more experienced pilots constantly look over the new guys shoulders. Also, even though the heli's do crash it's not near as often nor is there as much force behind them when they do. Remember we just do training so the hardest hit is from maybe 2 or 3 feet. Safety concerns at THS are different than the concerns at TWOH. If a battery catches fire in a parking lot you just toss it on the ground and let it burn out. Or if it catches fire during a race you may lose the car but you'd be hard pressed to damage the asphalt. Because TWOH is indoor carpet and sub-floored the chance a fire could spread is much greater. I think that is MasterD's concern.

Also, the idea that the useful life is slightly extended is not entirely true. New cells are released about once a season and each batch has a higher C rating than the previous batch. The increased C rating allows the batteries to be discharged at a higher rate without voltage dropping off as quick under load. The result is more power.

There are some other issues with lipo's. Because the only on-road class that runs 6-cell is touring if you plan on racing multiple classes such as 1/12th or oval you cannot use the same packs. Even though different packs are required there are many people that just change the configuration of there packs to suit what they are running. Taking old race cells and breaking them up or putting them together for one reason or another. If you run touring through the summer and 1/12th thru the winter would you rather buy all new packs or recycle the cells you already have?

Just my $.02
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Old 03-22-2007, 12:31 PM   #171
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Yeah I understand. Losing a building versus messing up a parking lot or losing a 1:1 car is definately a big difference. Point though is that lipos are already being used there with the helis so its not completely new to TWOH. TWOH recently had a nimh explosion so I guess nothing is really safe. I see your point on the classes but unfortunately for now it seems this will be a TC thing. I dont think anyone is saying you should not allow Nimh for those that prefer to use it. In fact it seems nimh will have an advantage over lipo on the track so I suspect most of the fast guys will continue to use those.

Not that we need another class but Id love to see TWOH have a rubber tire, lipo, brushless 13.5 class. That way we can get more of the people from THS to move indoors and keep the cost week to week down a bit.
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Old 03-22-2007, 12:51 PM   #172
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Okay I have more questions.....

What does NiMh offer that makes them more advantageous to the racer? If the some of the faster guys at the track would still keep their NiMh for racing, what would the racers buy to try to beat the faster guys? I mean most people want to run the same stuff the guy who holds the track record is running, right.....? Since Lipo's could possibly be alot more dangerous if one were to ignite than a NiMh, and NiMh could possibly offer more performance, Why do we want to run LiPo's?

I am trying not to be against running Lipo but these are all questions I feel would be asked of me, so I am looking for answers. We all know information is a powerful tool.

Thanks
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Old 03-22-2007, 01:02 PM   #173
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Darren, my understanding is that nimh is slightly faster on the track then lipo but are comparably. Those chasing that last .1 second might decide they need to give up convenience for that extra .1 per lap. Ive never personally ran them back to back so Im not sure for an avg racer what the true difference is.

As for safety I personally feel safer with my lipo setup. The ICE hardly has any settings for the lipo - it just knows. Whereas the nimh charging requires me to set peak sensitivity and things like that. Ever since early Feb when a nimh exploded there Ive been ultra paranoid about the nimh cells. It was very scary for those that were there. Esp Mike who took the brunt of the explosion. Destroyed a charger and parts of the battery were found in the middle of the track (from the pits). Mike's comment afterwards is that he could have ran away from a fire.
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Old 03-22-2007, 01:11 PM   #174
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Quote:
Originally Posted by RTolle
Also, the idea that the useful life is slightly extended is not entirely true. New cells are released about once a season and each batch has a higher C rating than the previous batch. The increased C rating allows the batteries to be discharged at a higher rate without voltage dropping off as quick under load. The result is more power.
MrBlack, Ive heard someone else say this. How does Orion expect to handle this? Will they be releasing Lipos with higher C ratings?
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Old 03-22-2007, 01:15 PM   #175
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Quote:
Originally Posted by MasterD
Okay I have more questions.....Since Lipo's could possibly be alot more dangerous if one were to ignite than a NiMh, and NiMh could possibly offer more performance, Why do we want to run LiPo's?

Good question,

Here are some answers (based on our packs):

1. They are not more dangerous when done properly just the opposite.

2. No "voodoo regime" to keep the batteries running to potential

3. Far more consistant voltage (the "fast guys" will have the same power as the newb making it more attractive to potential drivers.

4. Less equipment lighter weight, as chassis change over and rule begin to comply the lighter wieght means tires last longer and less damage upon impact as car carries less momentum.

5. Cell life 10's of times longer then NiMH

6. More consistant power throughout run.

7. Longer run times.

8. Nominal voltage stays consistant from genration to generations i.e. 2 cells will be 7.4V last year this year next year etc.

9. No soldering needed for the highest quality cells and they come equipped to plug an play.

10. can be recharged emmidiately after run unlimited times in a day no having to have a box of packs for a race weekend.

11. No special storage case needed to keep the cells from shorting during transport, and no ris of shorting on tools and metals in pit areas.

There is more but I think you get my point.
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Old 03-22-2007, 01:58 PM   #176
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Personally I don't feel lipo's are any more dangerous than nimh or nicd. I've seen plenty of each type go up in smoke. I don't have any experiance with the orion packs either but I'm sure that with the protective case they are very durable.

Lipo's still need to be allowed time to cool before charging. And sure nominal voltage doesn't change between generations but then again the nominal voltage of a pack of 1400's 10 years ago is the same as the nominal voltage of the latest crop of 4200 and 4300's. I am also sure that eventually companies will begin to cell matched packs. In the end I'm sure that lipo's will become the norm. Just like brushless is taking over for brushed motors. There are just some major hurdles to overcome before that happens.
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Old 03-22-2007, 02:20 PM   #177
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great response Mr. Black.... and yes I do get the point. Or8ital when you mentioned that NiMh were faster I was thinking more like .5 or so.....I didn't think the difference was that small.

Hypothetically...........lets say I sold all of my NiMh stuff, I sold about a dozen NiMh 4200 packs, my Turbo 35 GFX, my trinity discharger, my overpriced battery case (lol), and a bunch of little misc stuff like a soldering iron, deans battery bars, flux......etc.

I want to make the jump to LiPo, and i know the when connecting wires that red goes to red and black goes to black. ( I mean i'm not a knucklehead but this would be new to me so bear with me ) To be the safest, and most cost effecient, what would anyone recommend I invest my hard earned dollars into? What's a good starting point with a fairly low learning curve? Keep in mind that I would need everything, because as of right now i have no go juice.

Darren
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Old 03-22-2007, 02:26 PM   #178
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1 Team Orion Platinum 4800 (~$100)
or 1 Team Orion Carbon 3200 (~$80)
Possibly two if you want to run more often. Charge time for the 3200 at 2C is approx 25min.

1 Lipo Charger (1 of the following)
Team Orion Avionics ~$80
Team Orion Advantage ~$150
Duratrax Ice ~$120
+ Power Supply to run charger

To Comfort the Race Director:
1 Liposack for extra protection when charging (~$30)
or 1 Battery Bunker (~$30)
or 1 ammo box

That should be all you need to run lipo. The batteries come with Tamiya connectors or you can use the 3.5MM (I believe that is the size) connectors on your ESC (Trinity R-Minus plugs)
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Old 03-22-2007, 02:29 PM   #179
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Quote:
Originally Posted by MasterD
I want to make the jump to LiPo, and i know the when connecting wires that red goes to red and black goes to black. ( I mean i'm not a knucklehead but this would be new to me so bear with me ) To be the safest, and most cost effecient, what would anyone recommend I invest my hard earned dollars into? What's a good starting point with a fairly low learning curve? Keep in mind that I would need everything, because as of right now i have no go juice.
1. Power Supply - I use the MuchMore PowerMaster Mini. It's a tiny 6.5A PS that's perfect for charging the 3200 and 4800 LiPo cells. I paid $55, and honestly for that price you can get a real power supply with more amps that could be used to do other things, like run a truer. I wanted something small and portable, though.

2. Charger - I use this one. I've seen similar chargers that I think might be OEM for a little less. It's tiny, like a little bigger than a deck of cards. Combined with the small PS, the total sum of your charging gear is smaller than most standard chargers. It's awesome.

3. Batteries - I've seen the Orion 3200 packs go for as cheap as $69. I've been using two of them to practice with and race in the club (sometimes twice a week) for about 5 months now with no decrease in performance.

I'm going to be building my Type-R tonight. I'll take a picture of my charging gear so you can see how diminutive it really is. That alone is a huge perk in my opinion.
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Old 03-22-2007, 02:36 PM   #180
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But don't sell the soldering iron, you'll still need that for the motors.
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