Electric Bikes – Battery Problems and other issues

After 1500kms, a few gremlins have crept into the batteries, in particular Lynn’s battery. It has cut out a few of times, once caused by a broken ring connector, the second time because a screw into the top of a cell came loose, and the third because a cell is out of balance, and is dropping down below the cutoff voltage for the BMS, which is shutting the battery down to protect it.

As I currently don’t have a single cell charger, it is hard to diagnose how terminal the cell problem is. It may just be very out of balance, and the charger and BMS between them are not allowing it to get back to full voltage, it is only getting to 3.2v (from 2.5v) when the rest of the cells are getting up to 3.6 to 3.7 (from 3.0v). Or it could be discharging internally causing it to drop its voltage quickly. As the increase in voltage is the same in both cases, the cell is not running away on charging, which is probably good.

As it was the negative terminal ring connector on cell 1 that was broken off, I am wondering whether the BMS has been struggling to manage the cells charge, and I am now reaping the consequences. The physical damage and loose screws are caused by the excessive jolting and jarring in our battery configuration, something we hope to fix over the next few weeks.

I have a single cell charger on order, which I will use to attempt to manually balance the cell with the rest of the battery. If this fixes the problem it will be good, and I have a way of fixing problems in the future. Just in case though I have two spare cells on order, and if I have to I will swap out the faulty cell. The other cell I will keep for when I need it.

On my bike, I noticed that the rear tyre is wearing quickly and unevenly. I have a feeling the wheel was not set up correctly when I had the wheels rebuilt at the start of the build. My mistake with the spacers, and the subsequent possibly unnecessary rebuild has been the source of much frustration, the mechanic I used to build the wheels was probably not up to the job. Any way, the wheel is possibly not running centrally between the stays, and may be a little misaligned in the forks. I will take the wheel in to have it checked at the local bike shop and if necessary re-trued etc. Of course, the wheel may just be suffering from excess weight and speed around corners! We shall see!

Posted in Electric Bikes

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