I own two of the older eco battery type units. I have had them for several years and experienced several problems along the way. The first issue was malfunctioning of the motor controller while under the warranty. Swytch replaced two controllers for me. The other problem was the 20 18650 cells in the battery became unbalanced over time and caused performance problems. I ended up opening up the battery packs and wiring individual leads to each battery set in order to balance them. This has helped significantly. I think the original BMS that was shipped with them was insufficient. I had another problem with the brake sensor that caused the unit to fail to engage the motor which I remedied by unplugging the sensor and not using it. Also, the LED display on one of the batteries doesn’t show the battery level unless it’s actually connected to the handlebar bracket and module, which is a minor inconvenience. However, after I made these modifications the kits remain usable as I am now able to balance the battery cells manually with a custom charger that I built myself using a series of 10 lithium ion battery charge control boards. I’m the mechanical engineer so this was something I could handle, but I wouldn’t recommend the average user doing this. I do recommend that swytch uses a better BMS for their products, or provide a balance charger.