Pack randomly doesn't charge

Hey guys,

I have this pack I built for a customer, all worked great for two month and now the pack sometimes doesn't want to charge.
I was at the customer's place and brought another new charger (72V) and it didn't charge with it also, so it's not the charger.
I took the pack back to my lab and it did started charging (with both chargers) so while it was charging and had the pack open on my desk I started jiggling all the wires, shaking the pack, applying pressure to every solder point and nothing, it's all super solid, looks perfect and keeps on charging.
I checked pack balance and it's all perfect.
The customer told me that sometimes he needs to ride it and lower the capacity for it to charge and it works most of the times (not all) but since I tried it at the customers place when it didn't work I took it back to my lab without discharging it and then it worked.
Could it be something with the fact that it was connected to his controller and maybe the controller was somehow making this weird problem?
Now everything seems fine and I can't recreate the problem but I don't wanna return the pack without me actually fixing anything as I wanna make sure that the problem will not come back.

Any ideas what could it be?

rg12 said:

Could it be something with the fact that it was connected to his controller and maybe the controller was somehow making this weird problem?
Now everything seems fine and I can't recreate the problem but I don't wanna return the pack without me actually fixing anything as I wanna make sure that the problem will not come back.

Any ideas what could it be?

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Seems unlikely something in the controller would cause a charging problem. More likely a BMS problem. Without any testing, I would guess there's an intermittent connection on one of the components in the BMS. If you can replace the BMS easily, that would be a good move.