Hello, I am a newbie here and to metal detecting. I just got the Garrett ADS 3 VLF/TR metal detector from Ebay and it seems to be in great shape, but it has 4, 9 volt NI-CD rechargeable batteries that are actually 7.2 volts at 75mAh made by SANYO. My question 1, can I just buy 4 new 9 volt rechargeable...