Sorry for the dumb questions. I was using my 6P with a M61 on two AW RCR123s and I let the batteries run until it shut off. I used it two times after that for about 5 seconds and it was really dead and no longer turned on. I had had a feeling that the batteries were low and most likely needed to be charged. I normally check the voltage and charge my batteries when they are around 3.8v. I always check the voltage on my batteries that have been drained before I charge them and saw that one battery had 3.32v and the other one read 0.00v on my DMM. I also had put the batteries to charge on my WF-139 and the slot charge indicator light where i put the 0.00v battery turned green like it was fully charged. I wiggled the battery thinking it did not make good contact and finally it went red showing it was charging. The 0.00v came off the charger at 3.16v and the 3.32V battery took like 5 min longer to charge and came out at 3.17v. Also I know you are not supposed to mix batteries with different voltages, but do they have to be exactly the same voltage or what is the voltage gap/difference that would be OK. Like a 4.10v battery and a 3.93v battery is the 0.17 difference too much? Thanks.