I was really happy with this setup, easily working on a 40l waveboard. However, now it looks dead: After a two weeks pause, I tried to charge my battery, which I left at 50% in the closed box. However, the charger does not charge and the remote control cannot connect. By taking out the battery, I discovered a small amount of water in the box. I had a small water intrusion a month ago because of a incompletely closed battery box but after pouring out the water and drying with a tissue I had several sessions without problems. The current charge of the battery is at 7V. Is the battery dead or it’s the electronics of the box or both? Is it possible to repair it or I have to buy new parts?
7V for an 8s battery is 0.9v per cell, if that’s the cell voltage then unfortunately your battery is dead, but it could be just leakage voltage from the (shut off, or damaged) bms that gives this low reading.
If it doesn’t take charge at all then you should try measuring voltage directly on the cells to verify what the true voltage is, it’s probably dead so opening wrapping won’t matter.
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Well, today I opened the “dead” battery. It looks like that. 24 Molicel P42A cells. Would it be a 6S4P architecture? (the official numbers of 28.8V/12.6Ah obtained with 24 3.6v/4.2Ah cells suggest me rather 8S3P…) The voltage of each 6cell packs was around 2.2V.
By curiosity, I plugged in the charger and it started to charge! Now I’m charging it slowly and under control for heat buildup, noise etc. For the moment I’m at 31V (each 6pack at 7.7V) and still increasing steadily. At pauses at 28V and 29V it held the charge over one hour. It allowed me to check already that the box electronics and the motor are OK.
Now I plan to fully charge it to 33V, leave for the night at a safe place to see how it keeps charge than decharge it with M9 Toolkit RC charger. If everything looks fine, I will bring it to a Li-ion battery repair store here to redo the wrapping correctly.
I guess that the cause of my problem was not water, but the sad fact that I left the battery in the box plugged in to the motor for two weeks (I should have better read the manual!) and that discharged the battery through Bluetooth etc.
Good news, but take some precautions with this pack in the future, going below 2.5V will have caused some damage to the cellsđź‘Ť
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