Hmmm. I'm not sure. I'm assuming the Horizon balance leads are just split "Y" for each of the 4 cells. So in reality, it's not balancing 8 cells. I don't know how smart this smart cap is to recognize 8 cells. Think of it this way: The smart cap has the 4 wires for balancing the 4 cells in the DJI battery. You tap into those 4 wires to make essentially the horizon adaptor. When charging, and discharging, I don't think it's seeing 8 cells. How is it able to balance 8 cells? Maybe I'm wrong. But regardless, I think using an external charger that you know for sure is balancing the cells on the external batteries is fine. Why would there be such a difference between me using my DJI 2x2S split packs vs G6 2400s? I did nothing different. Charged the main DJI battery and topped off. Charged the externals to 4.35v.