Its not the voltage that matters as much as the MAH that the battery can handle. You can get 4 AA rechargable batteries at 2600 mah that will outlast a higher voltage battery at only 1500 mah. I use Duracell 2600mah rechargable batteries and I get alot of run time out of them. The only difference that you will notice in the slightly higher voltage is quicker response. You will get quicker response from a alkaline at 1.5v=6v than you would a rechargable at 1.2v = 4.8v. So its a give and take. I would rather have the longer run times.