jon.mark.wright
Hi all,
After a flight over the weekend I had a little but of a rough landing with one of my planes, and the battery took some knocks on landing. It was only on a grass field but still hit the deck quite hard. I noticed today that the battery is all puffy which I presume is from that. Now the question is, is it dangerous to still use this battery, to charge it and fly with it? Or could it explode?
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F1wanabe
Hi Jon,
The puffed battery usually occurs if it was used with a power system beyond its "C" rating. I have taken a few good knocks with batteries and they have bent, but not puffed. What is the c rating of the battery, and how many watts is the motor? I would not risk charging a battery that is puffed though.

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e3_Scott
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Hi all,
After a flight over the weekend I had a little but of a rough landing with one of my planes, and the battery took some knocks on landing. It was only on a grass field but still hit the deck quite hard. I noticed today that the battery is all puffy which I presume is from that. Now the question is, is it dangerous to still use this battery, to charge it and fly with it? Or could it explode?


Hi Jon, my tuppence worth based on what I saw at my flying field today. An older gentleman was flying his high wing foamie, the battery was an older Rhino that was a bit puffy and he drilled the plane in very hard, wrote off the front 8 inches of the plane, we had to get a stick and dig the motor out of the ground.

Anyway, the battery was a bit warm when he picked it up and carried it back to the "pits", but about 5 minutes after the crash, one of the cells just burst into flame, horrid nasty white smoke and fumes.

I have heard of people charging puffed batteries as long as they weren't puffed too bad, but they are definitely a more risky proposition than a battery that has retained it's shape. From about three very hard crashes (luckily none of mine) I have witnessed in the past months where lipos burst into flames on impact or shortly after, I always check my battery if I have a very rough landing just to make sure there is not split in any of the cells and I always lay it on a rock for a while if I hit really hard, just in case the same thing happens as happened to this gentleman today.

So far, fingers crossed and touch wood I have had pretty fair luck with my lipos, but they do need to be treated with care.

Cheers,

Scott
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KennyCrash
+1 to f1s comment.

I ran my NTM 2700kv motor that needs a 35-40c battery with a 25c battery and it got puffy and hot. I wouldnt recommend charging it again though I know many people that have puffy batteries and just wait for them to explode. I like to keep safe with my batteries.

This is what I follow

"Discharge is the amount of power the battery can 'push' out and the number shown '20C' is an multiplication of the capacity. For example; A 20C battery can discharge at 20 x 2,000mAh which is 40,000mAh or 40Amps."

so pretty much if you are pulling more that 30-40 amps then you are pushing the battery to the limits.
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p51funfighter
F1 is right. I have done this. I think the real danger is when you charge it. I wouldn't put it on a rapid charge or charge it before it cools after using. I had mine catch fire and burn up. Just respect it or toss it. I have a steel bucket with 3/4" holes drilled around the base to put wires out to charger. If you toss it, dispose of it properly.
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breaker1crazy
I've used SLIGHTLY puffy batteries before and yes they do work, but it always scared me, always worrying about my plane exploding. On top of that i noticed it doesn't have as much power, so in my mind at least that would make me think you have to run the battery harder which just makes the condition work. What i would do is keep it but not use it on any plane you value or has good parts, wait until you get servos that have taken a beating and a motor on its last breath. then slap together a little fun project and do something stupid with it, just please don't try and make the local news.
"oh my gosh it works! look at that its flying, wow thats",(BAM!)..."never mind."

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KennyCrash
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I've used SLIGHTLY puffy batteries before and yes they do work, but it always scared me, always worrying about my plane exploding. On top of that i noticed it doesn't have as much power, so in my mind at least that would make me think you have to run the battery harder which just makes the condition work. What i would do is keep it but not use it on any plane you value or has good parts, wait until you get servos that have taken a beating and a motor on its last breath. then slap together a little fun project and do something stupid with it, just please don't try and make the local news.



Yes!

By project you mean exploding it for scientific reasons

Everyone loves to see someone stab a lipo with a screwdriver and see it explode on youtube.....
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p51funfighter
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Yes!

By project you mean exploding it for scientific reasons

Everyone loves to see someone stab a lipo with a screwdriver and see it explode on youtube.....

BB guns work too
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Jeriah
I've shot 3 lipos before with a shotgun. They all didn't work and a puff of smoke came out of them!


If you were inside your plane... You would never crash.
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jon.mark.wright
Many thanks for all the feedback. I really appreciate every bodies input. And I'm now thinking that battery will be disposed of now. I can only assume the hard landing damaged the cells some how. As that battery with speed controller and motor is my standard setup on all my planes so not sure what went wrong. I can't remember at the time anything feeling particularly warm. Strange. Thanks again.
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LukeWarm
You CAN continue to use a battery after it has puffed.
I have used puffed batteries for over a year after they started puffing, most continued to work almost like a new battery. The battery is not bad, it is just less than perfect. The only difference is; the capacities may have change a little so pay attention to the temperature it is at after you use it, charge it at half max or less, and Use it at its new capacity. You should mostly judge a battery by its performance, but keep its imperfections in mind as you use it.

The puffiness isn't gas, do not puncture the covering. The puffiness is the materials the battery is made of are beginning to swale (expand). A battery will only puff if you misuse it by overheat it, this shortens the batteries life and decreases its capacity. The best you can do, is make sure you set up the charger correctly, use a balancing charger, and use the battery without overheat it. Always charge on something fire proof and babysit your charging batteries. There are many things that can make a battery puff, it's nice to know how to avoid this problem.

PUFF RULES, How to take care of your battery:
A battery will puff up because of the speed or amount it was charged or discharged, or the way it's stored. This will result in overheating and the laminates will begin to separate. Overheating usually occurs because;
It was over-discharged
It was used near or below its 3.1v per cell minimum voltage restriction. When you feel the battery getting low, cut the power, glide and land.
It was over-charged
A LiPo should never be charged to more than 4.2 volts per cell. For a 3 cell lLiPo, that's 12.6 volts.
Often, when charging with two wires (a non balancing change), the cell with the least resistance will charge faster than the rest. On a non balancing change, all the charger knows is to stop at 12.6 volts. That's cell number 1 at 4.1 volts, cell number 2 at 4.0 volts, and cell number 3 at 4.5 volts. Cell number 3 is dangerously over charged, yet the charger did its job correctly. A balancing change always stops right at 4.2 volts per cell. It is for this reason I always do a balancing change; not only is it safer, but the batteries perform better and last longer.
It was charged too quickly
It was charge at too high of a rate. A 1800mAh is the same as 1.8Ah, a 1.8 amp rate is the maximum recommended rate (max) and will take 1 hour. I have seen many a fiends battery destroyed like this, I would never charge at this rate. I would use half this (.9 amps). It will take 2 hours but it is always safe, your battery will have a longer life, and the charge will always be problem free. ".2 amps" below max (1.6 amps) to half max (.9 amps) is safest; the closer to half, the longer the battery will last. Charging at less than half max has no advantages.
It was discharged too quickly
It is used in an application that called for a higher C (current) rating than the battery could handle. The 20c, 25c, 30c rating needs to be used with the "mah" rating to calculate the allowable amp draw. The number of cells does not matter.
2200mah/1000 x 25C = 55A; so mah/1000 x C = Amps.
55 amps is the maximum safe current a motor can draw from this battery.
You left it in the sun or a hot car
A LIPO will puff setting in the sun or a hot tool box. Also, If you start a flight with a 120°F battery, you have very little head room before it puffs. Keep Lipos away from excessive heat.
The weather you fly in
A LiPo will run a lot hotter on a hot summer day than it will in the winter. On a hot day, have at least 10 amps of headroom in the C rating. The internal resistance is at its lowest when they are ran with a starting temperature between 90°F (32°C) and 100°F (38°C). Do not start with a battery that is too hot or too cold.
You stored the battery empty
Store a battery with at least half a charge. This way, when they self discharge over time, they will never fall below the 3.1v per cell minimum voltage restriction.
If you connect two batteries, they must both be fully charged to the same voltage
If you use two batteries on a Y-connector, if they are at different voltages when you connect them, they will quickly equalize. This will cause them to both exceed their C rating and puff.
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jon.mark.wright
Thank you so much luke for the very detailed explanation. It was a very good read and iv just learnt a lot more about lipo. I think I may buy one of them lipo charging pouches that are like a safety pouch. Cheers jon
Check out my Youtube channel :
http://www.youtube.com/user/jonmarkwright
All my plans, build videos, and flight testing is available to view or download there.!
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ghostrider03z
Puffy batteries are "safe" to use, until they continue to get more puffy. By the way, what motor, battery and esc were you exactly using?
Crashing is part of learning. If you don't have any, it's like getting an F
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LukeWarm
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Thank you so much luke for the very detailed explanation. It was a very good read and iv just learnt a lot more about lipo. I think I may buy one of them lipo charging pouches that are like a safety pouch. Cheers jon
You are welcome. A safety pouch is a great investment, it's so much more portable than a large rock or tile.

A big key to avoiding problems, is to label then check the heat on your equipment after every flight. Keep records of you observations and problems so you can make the appropriate adjustments. Knowing your equipment well will make you a better pilot. Most pilots do not like surprises.
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