Connecting a battery improperly

fond of bikes

New member
Local time
8:26 AM
Jul 16, 2020
I bought an A2b ebike with a no good proprietary battery. The bike was 11 years old. The manufacturer did not offer replacement batteries. I did not want to pay the price to have the original battery rebuilt. All this was expected. I had a battery made up that would fit within the aluminum shell of the original battery compartment. I altered the ebike wiring within the aluminum shell to allow the new battery to work with the ebike. The end result could not be easily told from the factory setup. I used the ebike set up like this for a while. The battery on this ebike sat above the rear wheel. I thought the weight in this location made the bike unwieldy. I removed the original aluminum battery case. I moved the battery to the bottom of a pannier over the rear wheel. I had to extend the motor-to-battery cable. The cable went through the frame. The cable had an SAE connector within the frame. I bought a 3' 10AWG SAE to SAE extension cable 2-pin bullet quick connect cable to replace the original cable. Fishing the cable through the frame was difficult. I was about to connect the battery to the cable from the motor, but noticed that I would have a red wire connected to a black wire. I had to turn that cable end for end to put the red and black wires in proper orientation. The wiring is now all properly oriented. Red wires are connected to red wires. Black wires are connected to black wires. But this experience brings up the question: What happens when one connects up the battery backwards? Does anyone have any personal experience connecting the battery backwards? Would you please share that experience with us.
If you have any doubt a simple way is to connect a small fuse at the point you are connecting the wires
When I made up my 18650 battery I momentarily touched the BMS negative wire to a positive bank of cells :- Result a big flash and the BMS gone!!!