Whats not to beleive? Thats how its been done for a long time now. Set up one X4 to charge 4 batts, and the other to discharge 4 batt and feel the heatsinks. I garuntee the discharging one will be much hotter. Thats because it sends the current through a bank of ceramic resistors connected to your heatsink. If you wanna regain that energy make an adaptor to hook your charger inputs to your battery. It wont last long tho.