I charged the batts today and they got very hot. They melted the 1st 4 cell holder. I changed the holder to a new one. Hopefully it doens't melt this one as well. I set my charger to 0.3A. Should I set the final voltage to read 4.8v? Or let it charge to over 5v? I'm using it for DX3S on 4 AAs.