I have ZERO solder skills, and my first attempt was with the batteries in the wrong polarity position! A real Homer Simpson move. I got them apart, and still managed to resoder everything back together. Its been a month and its working as new. The shaver holds a charge for a week before charging, longer actually. I am so glad to have “saved” an older and fav-o-rite razor from the dump. Oh, and as a bonus bolo, I screwed up and ordered the wrong part number/wrong battery and the company refunded as soon as I returned it (USPS) and they sent the correct one . . .so if I have any advise it is to CALL them first and make sure you are ordering correctly as it is easy to screw it up.