Will Prowse published three cycle-test videos between 16 and 23 October. In each one, a battery that looked like it had a bad cell turned out to have a BMS problem.
The first is a Yixiang V3 314Ah kit with EVE MB31 cells and Yixiang's new in-house 200A BMS. After 150 cycles it delivered 299Ah, 8% below rating, and cell 1 hit 2.5V while the others were at 3.0V. Prowse swapped that cell out. Then, after asking Yixiang about the settings, he found the app's "balance modes" do nothing. Balancing only runs once "force active balance" and an "equalizing switch" are both on: "It had no balancing before." Once balanced, the pack delivered 310Ah at 160A, and the cell he had removed tested at 311Ah on its own. Prowse says Yixiang is changing the software.
The second is a WattCycle server-rack battery that lost capacity on every 50A cycle; the video title says 6% in 10 cycles. In the 23 October follow-up, cell 16 was the one running low, even though the 3A active balancer showed as on and working. That cell showed no heat, normal internal resistance, and delivered 101Ah on its own. Prowse concludes that the BMS draws more current from one cell during cycling. That is his explanation, not a measured mechanism. He says the same BMS interface and equalizing switch appear on a second brand where balancing is off by default and cell 1 is the one that drifts. From his description, that's the Yixiang kit. He doesn't name who makes the BMS.
A disabled balancer and a balancer that can't keep up look the same in the app: a full battery with a bit less capacity each month. One capacity test when the battery is new won't catch either; Prowse now calls his older single-test reviews "useless" (see our July Background). Neither company has commented beyond what Prowse relays, and we haven't contacted them. His videos carry affiliate links, and he runs Charged Reviews.
