For anyone from the future reading this, please do not super glue your balance wires on.
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Goddammit i just finished supergluing all the packs i was working on.
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i just finished using steel infused epoxy to glue my cells together
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if you think soldering is too much work, and you have welds that look extremely hot, battery building isnt for you. This is how you burn your house down.
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That was a foreseeable response and I should say some things so others donāt get a bad idea:
I use lifepo4 chem and have tested them and canāt get them to go into flames other than by being punctured. I use dischage balancers thatās barely burn any amps. I pot the battery so nothing is moving. I see no voltage drop along the balance wires. The welds are good. All n all Iām feeling safe.
Soldering balance wires on after already having welded a 24s battery is a lot of work and kinda defeats the purpose of welding in that Iām now heating it all up anyway with solder. soldering the balance wires on the nickel before welding wouldāve been good but too late now.
My question still stands and looking for other ways to attach balance wires as I have two more 24s batteries to build
Battery shorts that dump amps can set other things on fire from rapidly heating them up, thermal runaway isnāt the only danger.
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Because balance wires are much smaller gauge than series and even parallel connections, the amount of heat needed to solder them is much lower. Alternatively, solder to the tabs before welding them if youāre very concerned.
All that aside though, even if soldering after was the only option and definitely very bad, itās still better than not securing them properly. Thatās very dangerous, a loose balance wire bouncing around is Not Great, but even just a faulty connection that doesnāt stay in place will just cause a bunch of charging problems and headaches. CA isnāt good at handling vibration (as far as I can tell), and canāt make a good electrical connection
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Also, do you have any insulation going on between your P groups?
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Oh god
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The batteries are potted. Like this. I feel this is a replacement for insulation between p groups. And being lifepo4 I feel itās safe
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Youāve been around this forum for a while now, enough to hopefully pop into this thread every now and then. If your take away is that thermal runaway is the only danger with batteries then you should spend some more time reading. Short circuits anywhere can easily make enough heat to really do some damage.
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If itās potted I see no way for it to short. I could throw this battery down the street and I literally have.
So is the adhesive acting as both anti-vibration immobilization, and as structural support there? I would NOT trust it for the second task, since youāre actually just gluing to the shrink tube.
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If the cell wrappers still have contact with each other, thatās enough.
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The cells are fully potted not just the shrink. And as I say these cells ā¦ I canāt get them to go to flames no matter what I do and I do. I feel safer with this than any kind of ion battery.
Lately been thinking with ion cells, if they were to short, a really high power cell is a boon as it will blow away the short hopefully before it can send cells into runaway or cause a fire
Ok but death by fire isnāt the only risk here, even pretending that LFP canāt catch fire itās still very very bad if that pack shorts out. The device stops working, potentially with a rider on top, the whole assembly needs a lot of work to even assess what happened. Not burning a house down isnāt the bar needed for a successful build
Also physical abuse isnāt the only damage you can do to a cell, if a p group is shorted out but the pack is still drawing current youāre driving a current backwards through it and they do not like that
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Iāve shorted the battery a couple times to see. Thereās not much left to cause a short as the wires were blown off. Iāve built ion batteries and had them short and scared me badly with popping valves but this chemistry and also potted seems the safest thing possible. I get that you guys are looking for weaknesses and itās appreciated but Iāve done a lot of testing and ended up destroying the battery in the end just to see what would happen.
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Ok, so I build illuminated signs at my day job. Our 24V PSUs have short circuit, over temp, ground fault protection, etc. The frames are grounded, the sign materials are self extinguishing, all the bells and whistles. If you get a short, the worst case scenario is that some magic smoke tarnishes the sign and the lights go out. I STILL wouldnāt use that as an excuse to leave voltages separated by nothing but 0.3mm of PVC or use conductive glue for critical wires.
I think youāve shown that the risk of catastrophic personal injury is relatively low, sure. But this rubs me the wrong way because the strategy seems to be finding a maximum acceptable risk instead of a minimum possible risk.
I ride experimental vehicles at unreasonable speeds because Iām wearing as much body armor as I can buy and I seek out empty roadways, and then my brain rewards me with the happy zoom zoom chemicals. What are you getting out of this pack design, reduced build time? Not worth it IMO
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I donāt know if thatās a rhetorical question but I donāt see a risk of anything rubbing otherwise Iād be separating p-groups with something