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Old 08-23-2016, 10:36 AM   #21
octagon
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Re: Let's talk li-po battries.


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Originally Posted by RAMJET View Post
Charge them where you like, just make sure they are never out of your sight when charging(should be in something fire resistant when charging) . and have them stored in a fire safe box when not in use,even when in your car. People have lost cars and houses because of the hazards related to lipo batteries. I have pretty much stopped using them altogether because there are better and safer choices for my application so why even take the chance. does not matter if you have never had a problem, lipos are a potential fire hazard and you need to treat them as such or you will have a problem.
I was about 36000 feet up, over the North Atlantic on my way to Ireland when I remembered I had left a battery on my Hitec 4X charger on the storage cycle. I normally charge on the top of the washer that is located just outside my workshop. I have charged hundreds of batteries there without a problem, and frankly just got complacent about the never out of site rule. I thought of phoning one of the kids to come over and unplug the charger and put the battery away, but it was 1 am here when we landed there. I thought I would call later in the day, but, well, long story short I didn't, and in fact forgot about it for the next 2 weeks. We left on Friday night. Sometime mid Sunday the battery caught fire. I called Hitec and they said that even though the store cycle stops, the battery will still continue to drain. I don't know if that was the cause, but whatever it was the fire was intense. The burning material fell on some laundry in a wicker basket by the washer. That caught fire and because it was against the workroom door, that door caught fire. the fire burned up the door and the wall caught fire, and the open ceiling floor joists were just beginning to burn when a miracle happened. About 15 years ago I had wanted a faucet out the side of the house. The problem was there was a metal beam blocking a direct path from the copper cold water pipe to outside, so instead of soldering I used a plastic fitting and flexible piping. That piping burst and the ensuing deluge doused the fire, putting it out. The water continued to cascade down until our daughter stopped by the house about 4 hours later. In fact, water caused as much, if not more damage than the fire, but of course would not have happened if the fire hadn't have happened.
I have struggled with a way that would be safe to charge even if a fire did start. I have come up with a solution. I have a smoker BBQ I have not used in a few years. A BBQ is supposed to have a fire in it right? So now I charge on the grates of the old unit and if the worst does happen, and a battery does catch fire, it will be contained within the bbq.
I wanted to tell this story, because it is so easy to become complacent when charging.There were many times when I did not watch the charging process closely, and there was never a problem. I take full responsibility for what happened. Luckily, my insurance company has been unbelievably good, very generous and understanding. So I guess all I can say is make sure you are diligent when working with LIPOS. They are wonderful things and make modern electric flight possible, but they must monitored and charged in a safe environment.
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Old 08-23-2016, 11:48 AM   #22
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Re: Let's talk li-po battries.

Rob,

Thanks for telling your story....... from the picture it appears that some nearby models escaped unharmed.

The suggestion about using a salvaged BBQ is a great one which I had not before heard.

Btw, I store my lipo batteries in a bar sized fridge, just above freezing, both for safety and longevity.
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Old 08-23-2016, 01:09 PM   #23
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Re: Let's talk li-po battries.

Hi Michael,
That plane in the background is an eflite Beaver 25 on floats. The tail was close to the fire, and received some damage, and it was covered in soot, but is I think repairable. I had the wings for a Denight Special that had the covering shrink until it pulled away from the balsa, but again should be repairable. At the moment all my tools are in storage or being cleaned by the insurance companies cleaner. I don't even have and exacto knife! I had a couple of foamies hanging from the ceiling. They look like they are made of popcorn! with the horizontal stabilizers looking like a hound dog's ears hanging down.
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Old 11-20-2016, 11:47 AM   #24
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Re: Let's talk li-po battries.

Is there a reference link or discussion somewhere that goes over the failure modes of LiPo battery? I am trying to understand what goes on internally.

I have a battery right now that I will be disposing of. It is a 3 cell 11.1v battery, I am trying to figure out why it is showing 19.9volts and has fried two of my chargers before I figured out the battery is suspect.

I see in the reads if a cell goes low voltage it will puff then will probably burn up on the next recharge cycle. Also see that if user screws up on the charger settings or leaves unattended, an overcharge will puff and burn.

I am looking for explanation and understanding how a static over voltage can occur. This is a battery taken out of a 2 year storage. It has not been charged or overcharged. It shows high volts right off the get go.

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Old 01-05-2017, 06:16 PM   #25
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Re: Let's talk li-po battries.

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Old 01-06-2017, 02:17 PM   #26
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Re: Let's talk li-po battries.

Hi Claude. I have had a couple of batteries do the same thing you describe, only not as high a voltage.

One time I thought I would try to see what would happen if I flew a tired battery below my normal 60% discharge. I did this with a 2200 on a 450 heli. As a benchmark, I normally fly about 6 minutes in hover with a good 2200. On a tired battery, RPM drops off after one or two minutes.

So with the tired battery, I found that the RPM gradually got lower and lower as the battery ran down within the first minute or so. But then it did something funny. the RPM actually started going up. What???? So I kept the heli hovering while I ran down my timer. Landed and found the battery was extremely hot and very puffed.

And i also noted that one cell was reading 0 while the others were over-voltage.
I can only speculate that there must be some kind of chemistry breakdown in the battery that is permanently damaging it, this breakdown must be releasing a lot of energy in the process, resulting in a high voltage reading. These batteries are beyond salvation and must be neutralized before disposing

The only safe way to do that is to run them down to zero using a lightbulb that will slowly discharge them to short-circuit state. If your battery is over voltage, you will know right away as soon as you hook up the bulb. Say if you are expecting 12V and use a 12V bulb and it glows white hot, you know the suspect battery is putting out higher than 12V. In that case, hook up 2 12V bulbs in series and run the battery down that way. Of course, for safety's sake, do this in a fireproof area like the concrete stones on your patio or driveway just in case the battery puffs up.

PS- I have run batteries down to 0 using the light bulb method and I have not had any go awry. All discharge to zero with just a little pufiness. So I suspect having the breakdown in chemistry that causes the battery to overheat is a byproduct of a high discharge rate. the lower and slower the discharge, the less reaction in the battery.
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Old 01-06-2017, 05:33 PM   #27
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Re: Let's talk li-po battries.

Hi Max.
Have never heard of a lipo going over 4.2 volts. But always the first time though.
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Old 01-15-2017, 08:08 PM   #28
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Let's talk li-po battries.

Well, I've seen the high voltage which is why I asked. So I getting here based on Max experiment and observation ( thanks Max!) is that a battery that has gone high-voltage has irreversible damage. It may still be useable, under controlled conditions and a one timer to end it all. Then dispose of safely.
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