Ride safe - a short story of ride gone bad

Currently I just have stopped the motor like a leash error! But everything is possible!

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I see! I think a vibrating pattern on the remote would be best! No distractions and you still can get back to shore asap.

No wires should eve run underneath or on top of a pack. That’s incredibly bad design. All wiring other than inter-cell connections should run on the sides where there is zero chance of being snagged and with added insulation. This ensures there’s no chance of shorts. Even my busbars are triple insulated and run down the sides.

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Correct me if I’m wrong but the balance wires need to be connected on top and bottom of the pack to reach the different cells. Of course, you should always solder them at the extremeties of the pack and ran through the side but they still will be underneath and on top of the pack.

Run a nickel tab off the negative terminal and bend it over the side. That way the wire can only run off the side and its impossible to short on anything as the side of the cell is also part of the negative terminal.

Balancing wires can be connected to the end of the parallel cells nickel taps

Fusing your balance wires is actually not that complicated, I have used the fuses 3A below. This reduces the risk of failure when a short happens in one of the wires.
(in my box the cells lay on the side, so the balance wires are on the side of the pack without any pressure/rubbing)

https://nl.mouser.com/ProductDetail/Littelfuse/0471003MAT1L?s=Vv6sT79n3zQdYVF2cfN4GQ%3D%3D

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I run with BMS on-board batteries and no issues. And I had a set get wet and the packs were destroyed but they never caught fire. My battery guy said the BMS actually played a part in controlling the destruction. I will always use a BMS in my battery packs (I have three sets now). New ones have the bluetooth BMS.

Any bms is better than no bms! But thst said I highly suggest read the cells specs and adjust the parameters accordingly! Thermal constrains, discharge rates and voltage cut off they HAVE to have a margin of safety since it is not possible to find out the accuracy of these crappy bms out there! Also I see people never calculate the nickel taps maximum current tolerance! I Always choose or combine them with 25% extra room!

Its funny how we see patterns developing.

Whereas you see potential BMS problems, I see a home built batteries problem. (not sure if this is home built yet)

Im not saying you’re wrong or having a go, and I think there is a bit of a history of BMS problems out there by the sounds of it.

I think the reason I went for a manufactured battery is because there are too many minor mistakes to be made building a battery pack, and the results of those minor mistakes can be catastrophic!

I put my trust in guys that build the packs every day to do it better than I could. Its a lot of energy to go boom under your feet.

I have a BMS on my battery. :worried: I think if I see this happen to a manufacured battery, Ill be thinking about removing the BMS. Has anybody removed a BMS off a pack? I wonder whats involved?

Which BMS do you use ?

I did, nothing special, just opened it and took the bms out after reading all the BMS problems here. Wondering if I should put it back…

But you still have the balance wires in place?
Should those be fused?

Warning about removing the BMS…
I read about doing that in another forum for Ebikes, and I did remove my BMS…
I dont know if that was the problem or not but my battery did burn up almost taking the garage with it.
3 months renovating the garage… luckily the insurance payed for it…
Just a warning thats what im saying…

I think that the battery should have a BMS connected… that is the way I will go anyway.
Have a nice day everyone!
BR
Magnus

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So I still have the balance wires connected indeed. I am planning to use the BMS for charge only. Basically it means I am not using the BMS for something else than charging (so it doesn’t stay in my battery box). I have 15 pins connectors coming out of my custom battery case to connect the BMS during the charge, otherwise I would need to use a 14S capable battery charger with balance wires, which should be quite pricy if it ever exist.

Would you elaborate on this ? How did this happen ? Was your battery enclosed or not ? Any picture before the incident ?

I can’t motivate this enough! This is a very nice solution for DIY!

Sorry no pictures…
6s10p for a bike battery. The battery was mounted in the bikes battery module enclosure.
I had bought a charger in China, and the working theory for the failure is that the charger did not work as intended.
It was supposed to stop charging at 24v an after this just do maintenance charging and keep the battery at 24v. The charger just keept charging… and something overheated, the batterycase started to burn and this heat detonated the batterypack as a firecracker.
It blow the fire out thankfully…, :blush::+1:t2:

4 boards with mine : no bms , over discharge lipo : esc low voltage safety Cut didn’t work …

Did you (@JTAG) really see this problem arising?
Balance wires are >20AWG; 0.5qmm, so I see them basically as a fuse. Everything over 20A will burn them and then they are gone (gone like vapor, not being able to keep the shorting). But since (at least in my batteries) there is nothing easy flammable (that’s the reason why you should use kapton tape) it is not a real problem (beside the smell and the BMS shutting off).

I’ve seen this happening more than once, crossing balancing wires from ESK8s getting pressed in a enclosure and rattling there for a while. But you also see it often at LiPos when people use a parallel charger board and plug the balancer in wrong: a short hisssh, a nice spark and some of your balancer cables burnt. No real fire no explosions…
If you are lucky it is outside the isolation and you can repair it, if it is inside the pack most people throw them away (which is better than opening a LiPo with a kitchen knive…).

Beside the tiny balancers these china smartBMS are low side switching, so only connected to a couple of balance wires (22AWG: 0.3qmm) and the minus pole of the battery. No connection to positive. Even if the BMS wants to short cut your battery, it is physically only possible to do so through the balancers.
So can you (@Jezza) explain me why the BMS gets accused first, every time a battery goes poof?!

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I didn’t build the battery, I bought it. Sorry, but I didn’t take pictures before. And yes, it was fresh water.

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