I had the same problem with my GB40 1000w battery booster. I desolder the micro USB 6 pin board and remove it. Then I remove the micro USB connector at the end of the cable and strip the red and black wire 1/2 inch long.Pass the cable true micro USB opening and made a knot to secure the cable and solder the red wire to the 3 positive pin on the left and solder the black wire to the 3 negative pin on the right on the base board. I then charge the GB40 normally and everything work has before. I compare the unit with none good one and they are the same. Hope things work for you. yvandenis@msn.com