My car was starting very hard after some days of rest, so I tried to charge my battery. But the ctek refused to charge the BXT-40R at 12.45V, desulfatation and error. So taking the battery out of the car thinking of buying a new one, I heard some gurgle from the acid. So I opened the cells and refilled it with lots of destilled water. In two chambers the plates were dry on top. After refill, the ctek worked flawless. Is it like new? No, but I will get some more time out of it. I wish I had done this some years ago.