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Old Mar 02, 2004, 09:34 PM
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LiPoly Battery Explosions are REAL

My LiPoly battery exploded while being charged this evening. I do not recall the make of the 1100 maH battery, but I was using the Kokam Lipo-402 charger - that is not a slam, I am just reporting the set up.

Thank goodness I bought a Pyrex dish Tuesday!!! The only damage (other than the loss of my GWS Dragonfly and radio equipment) is a piece of remnant carpeting and two small (230 maH) batteries and a magazine nearby. I also have that lovely burnt plastic smell as a remembereance.

I will NEVER again charge a LiPoly battery in the plane. The fireball illuminated the upstairs part of the house, and it was 'around a corner' from the stairs!!!

I do not know if it will happen to you, but it happened to ME!!!!
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Old Mar 02, 2004, 09:50 PM
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First... Glad to hear damage was minimal.

Now... for the hand slapping. RIGHT from the sticky "Ultimate Guide to Lipos" on this forum:

4.NEVER charge the batteries unattended. This is the number one reason for houses and cars being burned to a crisp by lithium fires.
5.Use a safe surface to charge your batteries on so that if they burst into flame no damage will occur. Vented fire safes, pyrex dishes with sand in the bottom, fireplaces are all good options.

And now, a couple questions.
How far did you discharge the pack (to the LVC)?
What speed controller?
What LVC was used?

Again, I'm happy to hear you and family are safe.

WJ
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Old Mar 02, 2004, 11:46 PM
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WJ,

Thank you. I have to admit that I had not read the 'rules' until just now. My bad. I am not going to make excuses but I am going to wonder out loud how such a dangerous product made it to consumers without a better warning system.

I did not discharge the pack. I had been flying the DragonFly and the batteries were running down. One reason I went LiPo was because I was led to believe that they were better in all ways, the only drawback was needing a special charger.

The ESC was the recommended GWS ESC for the Dragonfly. If there was a programmable setting, I do not know what it is or how to set it. The English instructions were less than wonderful.

My fault, possibly. I am sure glad I bought that dish!!!
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Old Mar 02, 2004, 11:55 PM
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How many times had you charged the pack?

-Jim
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Old Mar 03, 2004, 12:47 AM
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"The ESC was the recommended GWS ESC for the Dragonfly"

My money says the pack was over-discharged (way below 3.0V per cell), and when re-charged, it caught fire.

GWS controllers are non-progammable. It might have been recommended by GWS, but it sure wasn't meant for Lipo use. It has a factory 4.3V Low Voltage Cutoff (LVC). Min LVC on a 2-cell pack is 6.0V.

WJ
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Old Mar 03, 2004, 02:43 AM
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What settings did you have on the charger? How long had you flown and with what motor, box, prop? Any and all details will help us all in the post mortum phase. Mabey someone else can avoid the same experience.

Larry
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Old Mar 03, 2004, 03:09 AM
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Hastings, Hawkes Bay, New Zealand (Aotearoa)
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My partners standard GWS heli (280 motor) uses 2 cell Lipo's and with the 1200's it will not hover if the voltage drops below 6.2v, therefore would be very difficult to over discharge the cells.

Heather
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Old Mar 03, 2004, 04:35 AM
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martimer,

You did the single best thing anyone can do for LiPo safety: You improved your charging environment when you started using that Pyrex dish.

I take it your pack is a 2s configuration. The cells in such packs can be charged in parallel, which (your charger remaining always set at single-cell voltage) eliminates a likely causes of your pack's exploding: one or both of the cells suffered overvoltage.

- RD
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Old Mar 03, 2004, 06:55 AM
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Quote:
Originally posted by RD Blakeslee
You did the single best thing anyone can do for LiPo safety: You improved your charging environment when you started using that Pyrex dish.
RD, I don't think you really meant to imply that using the Pyrex dish is the single best thing anyone can do for LiPo safety. In fact, the Pyrex dish allowed Martimer to charge the pack in the aircraft with the dish underneath, creating a false sense of security. Dish or no dish, this could have quickly developed into an uncontrollable secondary fire.

In my opinion, LiPo packs must be fully contained in a non-combustible environment that greatly reduces the chances of secondary fires developing. Since we know that cells have been known to spew burning embers many feet from where they were resting, and have in a few instances even taken off like pop bottle rockets, an open Pyrex dish is nothing more than fool's gold.
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Old Mar 03, 2004, 07:59 AM
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I have not kept track of the number of cycles. In my ignorance I thought that one of the reasons to go lithium was because you did not have to worry about charge/discharge rates (the charger was supposed to handle all of that which is why the special chargers were required).
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Old Mar 03, 2004, 08:09 AM
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martimer,

The Kokam 402 charger requires you to set both the number of cells (charge voltage) and the charging rate.

But that doesn't have anything directly to do with the number of charging cycles the cell(s) have undergone.

It is true that the capacity of a cell that has been charged and discharged many times, or damaged by overdischarging, will decrease in capacity and could possibly result in selection of too high a charging amperage.

But that's not so critical as overvoltage and unlikely to have caused your explosion. Overvoltage applied to one or both cells is more likely.

Overvoltage in both cells in a 2s configuration would be caused by selection of too high a voltage for the pack (over 8.4 volts nominal). Overvoltage in one cell would be caused by pack imbalance - a higher residual voltage build-up in one cell, lower in the other.

So, it's not so simple. - RD
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Old Mar 03, 2004, 08:18 AM
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hoppy's Avatar
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Martimer,
Sorry about your accident.
Please check your charger now and let us know what voltage and charge rate the jumpers are on. This is an important data point.
Thanks,
hoppy
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Old Mar 03, 2004, 11:44 AM
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Hey guys,

This is amost important thread as I jsut charged my first LiPo's last night with that very same charger. First off, the pictures of the Kokam's LED's did not match the actual product. They are pretty self explanitory, but it looks like an older version might have had separate LED's for "CHARGING" and "CONSTANT CURRENT/VOLTAGE" while the one I have has a single, orange LED for this.

Anyhow. I was charging a 3S2P 2400 11.1v pack. I set the charger to 1A, 11.1V. I plugged in the battery, plugged the charger to my power supply, and monitored it until the LED's started blinking (CHARGED and the C.C./C.V. LED). This took about an hour. The pack did not get warm at all. I was charging it outside on my patio table (stone top).

I have a few questions. I didn't find the instructions very clear on how to set the amperage. If 1000mAH = 1AH, then if you charge at 1A it should take an hour to charge completely... right? So 2400mAH = 2.4AH should equate to 2.4 hours to charge at 1A, right? The instructions do say not to carge at more than the Amp Hour rate but the charger only goes as high as 1.5 amps so this setup should be good, right?

I'm kinda curious why the charger only took an hour to charge the pack. They were brand new, and haven't been cycled (to the best of my knowledge). I guess it's possible they weren't discharged beforehand.

I've read some guides concerning the care and feeding of LiPo's, but I was wondering if the pack will give any indication before it blows; I mean, does it go from completely cool to blowing up in an instant, or does it gradually get hotter and start swelling? So far, the only indication I have that the pack charged correctly is that it was cool to the touch and that it didn't blow up... I haven't checked the voltage yet.

Sorry for the long post, but could someone also recommend a decent, cost-effective ESC to use with my pack? I was going to use an old 20A Zagi ESC (the motor is a Multiplex 450 Turbo) but I'm not sure this will work.

Thanks,
Mike
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Old Mar 03, 2004, 11:45 AM
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1A, 11.1V.

So do you guys discharge your lithium packs by running the motors until they stop or do you have dischargers?
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Old Mar 03, 2004, 11:58 AM
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Martimer, one of the cardinal rules of Li cells is that you absolutely must not fully discharge them the way you do with NiCd or NiMH. Li cells that are run down until the motor stops or through a discharger will be destroyed.

It's time for you to put your Li cells down, take a "time out" and study up on the fundamentals of Li cells. Otherwise, you are going to be having a lot of accidents, and risk damaging property and injuring people.

Have you read the sticky at the top of the Batteries and Chargers forum entitled Ultimate Guide to Lithium Polymer Batteries?

If not, please do everyone here a favor and read it carefully before asking any more questions.
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