I ordered two of the batteries from Gemini and charged them last night after receiving them. I'm using the MS charger and measured 8.39 volts (as I think I remember today) from the Gemini battery leads after the MS charger indicator turned green. After 24 hours the unused one is now measuring 8.31 volts, so my memory (the 8.39 figure) may be faulty. I used the other one for 1 hr 15 min tonight on high; it now measures 7.92 volts. I also charged a somewhat worn MS battery (about 1/2 to 2/3 original run-time these days) and measured 8.29 volts. With no load my MS charger measured 8.49 volts output. No guarantees on the accuracy of my DVM.

OBTW: The Gemini packaging indicated a 5000 mAh battery - yet another number from them.