E bike Battery Repair – How to Fix and Troubleshoot it

hey guys in this video I will show you how to repair an e-bike battery now the most common reasons of a faulty battery are number one the BMS has failed in this situation the battery will no charge or discharge number two some wires co disconnected or sold drink got detached you can easily visualize that number three some cells release less voltage than normal or have died completely in my situation I got a little bit from all first I dropped the battery accidentally and I got so called symptoms I could not use all the capacity and after a while the BMS died so I could not charge it at all technically what happened is that one of the cells on the corner over here got short-circuited after that it killed all the cells in this parallel group then the BMS died trying to balance these already dead cells what a sad story but enough talking let's get into how to fix this battery first I obviously install a new BMS with same characteristics 10 s with 20 amps as the old one once you get the correct BMS just plug in these series wires connectors into the BMS I could easily replace the wires as well but in my case they are okay then you will find three main wires which you must solve their own BMS like p- discharge negative C minus charge negative and B minus battery negative and you can as well have a look on the old BMS how it was connected and do the same on the new one from this point you can charge the battery and if everything is fine then you are good to go but usually if the BMS was faulty it's because one or more cells are faulty as well so next you can begin to visually inspect the cells soldering points as well as looking for physical damage of the cells or corroded metal then with a voltmeter you can check parallel groups and you should get similar voltage [Music] and as you can see on my battery I found the parallel group which has zero volts completely empty cells so from this point if you must replace some cells then take a pictures or draw the sales position and everything so you will know how to connect them back most of the cells have the minus terminal flat and the plus terminal with small holes around so if I look over here I can identify the cells of this parallel group and there are five of them with the minus terminal on this side so I will remove the nickel strips from these cells to avoid short-circuiting the battery while working on it do not touch these groups of cells next to the one you are working on like you see there are groups of cells soldered together and if you complete the circuit then you will create sparks or even fire also don't forget to wear rubber gloves this side is done the cells are free now I'm going to do the same on the other side and here you can actually see how a bad cell looks like all this metal is corroded and this cell have been short-circuited for sure I will remove this wire now since all the nickel strips are off I can begin to remove the cells right I think I have to cut the plastic case on one side at least second one third one so to verify once again these cells are completely empty and I'm going to take five new cells and check their voltage the new cell must have same voltage and amps as the old ones and on this battery they use 3.7 volts and 2200 milliamps all right so now I'm going to place the cells back in position from this point you might need a spot welding in order to solve that the cells without damaging them is not that expensive and it's a good investment if you want to build batteries at home you can as well use a soldering iron but the lifetime and capacity of the cells will be reduced alright now I will solve the new nickel strips on the new cells basically all the cells on this group must be connected to each other [Music] if you have a spot welder a good tip is to bend these copper nails so you can reach more cells when you want to solder all right one side is done now I will flip it over and take care of the other side positive terminals I will solder back this wire as well after I've done soldering up the cells are quite stable I'm going to check if this battery is charging that's the reason I'm carrying this plastic cover there is a charging connector on it and let's see if that light turns red and it does I hope you can see that here now since it is fully charged I can place the battery back in the case all right that was it if you liked this video give it a thumbs up and if you are new to my channel consider subscribing I will publish a lot of cool videos in the future so until then stay tuned and I will see you soon

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