Need to repair your e-bike battery? Learn how to troubleshoot and fix common issues with this helpful guide. Get your e-bike back on the road in no time.
If your e-bike battery suddenly breaks down then do you choose to throw it away and buy a new one, or try to get it repaired. A new battery is expensive, whereas if it can be repaired then the cost will be very low. This article will tell you how to repair a e-bike battery.
Now the most common reasons of an faulty battery are:
The BMS has failed, in this situation the battery will not charge or discharge.
Some wires got disconnected or soldering got detached you can easily visualized that.
Some cells release less voltage than normal or have died completely.
In my situation I got a little bit from all : First I drop the battery accidentally, 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 got short circuited, after that it killed all the cells in this parallel group, then the BMX died, trying to balance these already dead cells. What a sad story!
But enough talking let's get into how to fix the battery. First install a new BMS with same characteristics as the old one. Once you get the correct BMS, just plugin this series wires connect into the BMS. Than you will find 3 main wires which you must solder on BMS like P- discharge negative; C- charge negative and B- 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. Than with a voltmeter you can check parallel groups and you should get similar voltage. And as you can see on the battery you can found the parallel group which has 0 volts, completely empty cells. From this point if you must replace some cells than take a picture or draw the cells position and everything. So you will know how to connect them back. Most of the cells have the minus terminal flat and the positive terminal with small holes around, so if you look over here, you can identify the cells of the parallel group. So remove the nickel strips from these cells.
To avoid short circuiting while working on it, do not touch this group of cells next to the one you are working on. Like there are groups of cells soldered together and if you complete the circuit than you will create sparks or even fire. Also don't forget to were rubber gloves, after you can do the same on the other side.
Since all the nickel strips are off, you can begin to remove the cells. To verify once again these cells are completely empty. And you can take several new cells and check the voltage. The new cells must have same voltage and amps as the old one, such as 3.7 v and 2200 mah.
All right now it’s going to place the cells back in position. From this point you might need a spot welding in order to solder 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 life time and capacity of the cells will be reduced. All right solder new nickel strips on the new cells. Basically all the cells on this group must be connected to each other.
If you have a spot welder a good tip is to bend these cooper nails, so you can reach more cells when you want to solder. After you have done soldering up, the cells are quite stable, you should check if this battery is charging, you can caring the plastic cover, there is a charging connector on it. And when you see that the light turns red, and it does!
Now since it is fully charged you can place the battery in the case. All right, this completes a whole battery repair job. If there is anything unclear you can tell us in the comments below.