I have a radio that runs on 8 x AA and they (thoughtfully!) put 10 slots in there; if you're using 1.5v throw-aways, there's a pair of little jumpers you can install that look just like AAs ... but if you use rechargables, you can just put 10 in to get the full 12v :-) I'm surprised that you can't run a 6v radio with 4.8v tho ... are you sure that the batteries are good?