To our valued client: We ensure that each controller board is brand new and programmed and well tested before delivery. When you meet the issue after you replace the new controller board, pls kindly talk to us first, pls don't open the case immediately. Thank you. Before you buy the controller board, pls kindly make sure your bluetooth could be connect. Otherwise , you need to buy both the controller board and bluetooth board at least. Error code 25: You need to be prepared that the following three spare parts are broken: controller board, bluetooth board, as well as the BMS board which is the protection board for the battery. When your model appear below situation: the battery display showed half or zero, beep twice and then five fast beep while the lights flash, which means the controller board, bluetooth board as well as the battery have the issue. Pls kindly note that series number is NO NEEDED, already programmed. Thank you.