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Apr 23, 2016, 08:18 AM
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Help!

Need your advice about rebuilding Lipo battery's!


I was writing on a Swedish board, saying that I took one bad cell away from my 4s battery pack making it a 3cell instead of throwing the whole pack away. People called me crazy, and explained the risks with dealing with lipos. I hope I know more than average about the risks, and I think I play it safe! Always charge and store in a ammo case, have fire alarm, extinguishers, have a good charger (I charger) etc.

One issue was that you can mess up things when you transfer to much heat from the soldering iron to the battery. Another was that you can short cut the poles on the battery, making it catch fire.

Did a experiment, clamping a soldering iron into a Lipo cell. After 4minutes the temperature was 90 degrees fahrenheit, (32 celcius).
How much heat can you expect the Lipo to handle?

lipo heating (1 min 30 sec)


What do you guys think? Am I stupid modifying my Lipo batterys?



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Apr 23, 2016, 08:46 AM
Space Coast USA
hoppy's Avatar
Looks like you have a piece of something between the iron and the battery.
You have it mounted on the top of the iron? What's the temperature on the top of the iron?
Soldering iron? Looks like a covering film iron.
We know that it takes a lot higher temperature than that to melt solder so the tab itself is at 350F or so.

But all in all, the idea of heating a lipo cell is outrageous as the thermal runaway temperature can be as low as 180F, well below the capability of a soldering iron.


But many here modify lipos. Discharge to 3.2V/cell to minmize fire potential. It's true that too much heat on a tab can cause the hermatic seal to be compromised alowing air into the pack. Is it safe? Depends on who is doing it. Someone who would heat a pack with a soldering iron?

But then again, maybe I'm not analyzing the situation correctly.
Last edited by hoppy; Apr 23, 2016 at 08:54 AM.
Apr 23, 2016, 09:20 AM
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i just modified a 4 cell to 3 cell after a catastrophic failure of 1 cell... i used the only iron i ever use my ungar 80watt w a 3/8 wedge tip.. took less than 1.5 seconds to melt solder on contact board and to reach + wire lipo terminal only got to 100 degrees with a ir temp gum all went good..
Apr 23, 2016, 10:08 AM
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Quote:
Originally Posted by losi man
i just modified a 4 cell to 3 cell after a catastrophic failure of 1 cell... i used the only iron i ever use my ungar 80watt w a 3/8 wedge tip.. took less than 1.5 seconds to melt solder on contact board and to reach + wire lipo terminal only got to 100 degrees with a ir temp gum all went good..

Thats what Im trying to prove! That you really having a hard time if you should heat the battery to dangerous temperatures!


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Apr 23, 2016, 10:22 AM
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Thread OP
Quote:
Originally Posted by hoppy
Looks like you have a piece of something between the iron and the battery.
You have it mounted on the top of the iron? What's the temperature on the top of the iron?
Soldering iron? Looks like a covering film iron.
We know that it takes a lot higher temperature than that to melt solder so the tab itself is at 350F or so.

But all in all, the idea of heating a lipo cell is outrageous as the thermal runaway temperature can be as low as 180F, well below the capability of a soldering iron.


But many here modify lipos. Discharge to 3.2V/cell to minmize fire potential. It's true that too much heat on a tab can cause the hermatic seal to be compromised alowing air into the pack. Is it safe? Depends on who is doing it. Someone who would heat a pack with a soldering iron?

But then again, maybe I'm not analyzing the situation correctly.

I don't know if you are analyzing the situation correct? Its a soldering iron, I think its called that. Or soldering station? A picture will help for sure!

Name: ImageUploadedByTapatalk1461424387.677989.jpg
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The soldering station is set to 450 degrees Celsius. The temperature of the battery is registered about 1 inch from the soldering pad.


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Apr 23, 2016, 10:37 AM
Registered User
It is possible to overheat a lipo, it's not easy but it's possible. It is possible to short out a battery but it's not difficult to avoid.

It's also possible to put your hand into a rotating propeller or to step out into the road in front of a bus...but most of us avoid those too.

If you have an idea what you're doing and are even reasonably careful, modifying lipos is not a big deal.

Steve
Apr 23, 2016, 10:56 AM
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its safe as long as you have soldering skills if not best to buy another.
Apr 23, 2016, 11:24 AM
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Another question when Im in the mood! how bad is it to short cut the battery cells? I mean, the battery is designed to give you loads and loads of Amperes! So how bad is it to short cut the poles for a fraction of a second?


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Apr 23, 2016, 11:24 AM
Space Coast USA
hoppy's Avatar
Quote:
Originally Posted by Turbotom2
I don't know if you are analyzing the situation correct? Its a soldering iron, I think its called that. Or soldering station? A picture will help for sure!

Attachment 8925513

The soldering station is set to 450 degrees Celsius. The temperature of the battery is registered about 1 inch from the soldering pad.
Hard for me to tell what you are doing from the picture. Looking at it again, now it looks like you have it sitting on a snow shovel. I mistook that shovel for a covering film iron.

I was expecting to see a picture what you were doing.....views of the soldering pad and soldering iron for example.
But the problem to look out for is getting the foil seal hot and destroying the seal.
Last edited by hoppy; Apr 23, 2016 at 11:29 AM.
Apr 23, 2016, 12:43 PM
Registered User
Quote:
Originally Posted by Turbotom2
Another question when Im in the mood! how bad is it to short cut the battery cells? I mean, the battery is designed to give you loads and loads of Amperes! So how bad is it to short cut the poles for a fraction of a second?
If it is a SMALL fraction of a second you often get away with it. But it's a much better idea just to be careful. A short circuit will draw much more current than the design allows (which is why if you leave it shorted too long the tabs/wires will start to melt).

Steve
Apr 23, 2016, 03:19 PM
Frankenstein recycled packs
rampman's Avatar
I try to get in, get done and get out in 3 seconds or less.
I set my 6mm tip's soldering station at 850F.
I am NEVER on for longer than 3 seconds.
More than that can heat the seal around the tabs and allow the cells to be exposed to air which kills it over time...a few weeks to few months.

Cheers, Rick
Apr 23, 2016, 06:51 PM
Registered User
When I hear people say you should never modify a lipo pack, I just laugh. Way back in the dark ages, we HAD to build the lipo packs ourselves. No balancing, no lipo chargers, we had to watch and monitor the pack with multi meters when charging.

I have taken a cell out of a 6s to make a nice 5s, taken 3s to make a 6s, 2, 2s to make a 4s. Had a crash, I was using (2) 3s batteries in a 6s setup. Lost the top cell in each pack. So I made a 4s pack out of the good cells.

As already stated, get in, get it hot, get out. Don't waste time and heat.


Buzz.
Apr 23, 2016, 11:52 PM
Registered User
Thread OP
Thanks guys! I got answers for my questions! 👍


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Apr 24, 2016, 10:11 PM
Registered User
Nothing wrong with rebuilding a pack, just do it carefully. If you discharge it down to around 3.6V per cell first there is virtually no energy left in it and a fire is all but impossible.


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