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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 26th May 2021, 10:19 am   #21
Glowing Bits!
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Default Re: Attaching to 18650 Li-ions

These batteries can withstand heat for a while but there is a limit as to how long the heat can be there for before a thermal runaway condition occurs.
I use these batteries everyday and use them hard, they do get hot but not dangerously hot, it's called vaping.
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Old 28th May 2021, 6:31 am   #22
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Default Re: Attaching to 18650 Li-ions

Quote:
I think it might be potentially dangerous to introduce a heat source to a LI-ion battery due to risk of fire/expolsion.
I had no trouble and was very careful, as mentioned the dwell time was kept very low. Also I used plenty of flux which ensures good solder flow and a quick joint. I also gave it a good blow afterwards, the battery being warm to the touch but not hot. If anyone trys this and is worried keep a bucket of water or sand by the bench.

Andy.
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Old 28th May 2021, 6:46 am   #23
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Default Re: Attaching to 18650 Li-ions

A bucket of water won't stop lithium from burning, it has a violent reaction to water, similar to sodium.
Been there, done that, the underwater flames look quite pretty!
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Old 28th May 2021, 7:00 am   #24
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Default Re: Attaching to 18650 Li-ions

Another thing I forgot to mention was that the batteries should be in a flat state before applying any heat to them, they do self charge up to a point when heated, doing this to a charged battery runs the risk of thermal runaway, the upper limit for charging is 110%, most chargers stop above 90% to factor in self charging.
The above is from my own observation, other chemistries do not exhibit this strange behaviour and are considered safer.
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Old 28th May 2021, 9:04 am   #25
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Default Re: Attaching to 18650 Li-ions

If you find soldering the tags fiddly and irritating you can bridge the gap with a bit of copper out of some discarded mains 2.5mm T&E cable.
Clamp the copper onto the tag with a small mole grip (this will act as a heat disperser) solder, then ditto the other tag.
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Old 28th May 2021, 10:19 am   #26
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Default Re: Attaching to 18650 Li-ions

Hi
I have often repaired Camera/drill packs that use these cells and have very little space for interconnecting wires. I have found that solder wick with short pieces of heatshrink over them makes a good substitute for the metal strips welded to the original cells. I always treat these with respect and apply lots of heat for a very brief time. best done out doors or by an open door/window
Kind regards RT
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Old 28th May 2021, 4:47 pm   #27
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Default Re: Attaching to 18650 Li-ions

OP here and thanks for all the hints and tips.

I bought 4 cells and a charger (before asking advice...) and charged them up before trying to attach connections. I didn't know tagged versions are available. Anyway, not knowing whether the device's charger circuit was even functional, I thought charging the cells up before starting the assembly would give me the best chance for the inbuilt circuitry to work. And if it doesn't, I could make an assembly that just has the 3 cells and I'd have to charge them up externally.

It was certainly great advice to use flux after sanding the cell surface. Normal multicore solder's flux just wasn't enough. I'm well on the way to completing the 3-cell assembly prior to attaching to the device's charger circuit, and no mis-haps so far.

Thanks again and I'll update this thread when there's more news.
Graham
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Old 31st May 2021, 6:35 pm   #28
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Default Re: Attaching to 18650 Li-ions

Having scribbled connection details onto the original cells as I disassembled the battery pack it was fairly straightforward to reconnect and re-assemble the pack. Into the multitool it went and sadly the symptoms were just the same as they were when I suspected the original battery pack. (A burst of activity and then nothing).

So I'm now left suspecting the speed-control circuitry in the tool and it may turn out that I could replace the original cells. But for now, the title of this thread has been done, I think. Lots of useful gen revealed, thanks.
Graham
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Old 31st May 2021, 7:29 pm   #29
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Default Re: Attaching to 18650 Li-ions

Fixed - the Aldi Multitool that is. Nothing so complicated as the control electronics. The connections to the motor have rubber sleeves over them. Inside one rubber sleeve the conductor was severed so was only being held slightly in place by the rubber sleeve. As soon as the motor started to turn, the connection was broken. Oddly, the tap it, shake it test didn't throw anything up.
As a happy llama I'll cease spitting for a while.
Graham
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Old 31st May 2021, 7:33 pm   #30
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Default Re: Attaching to 18650 Li-ions

As Grahams problem is now resolved time famish this one off

Cheers

Mike T
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