My 2 batteries worked fine for a month. Then the BMS on one died. After a week of email exchanges, wattcycle agreed to send a return label. It took a week to send it, then a week for the battery to get back to California, then several days to ship the replacement and a week for it to arrive. The new one is working now. I went a month without a battery and I worry that the replacement may also fail.But I was pleased that Wattcycle did provide the replacement.