Canon G2 Battery Problems

Hello all, I normally inhabit the Panasonic forums but today I bought a second hand G2 that I plan to convert to full time Infra Red.

The camera is in really great condition and comes with the original Canon Wide angle and Telephoto supplemental lenses. The problem I am having though is with the batteries, the camera came with 2 canon originals but neither of them last, i got 4 shots out of one an just over 30 out of the other.

The charger is built into the camera but I also have an Hahnel Ultima which plugs directly into the mains socket, both chargers show the batteries as flat and then fully charged within 5 minutes. Does that mean the batteries are DOA?

The seller says its normal and they are probably suffering from a memory issue and need cycling. I have charged them 6 times now (as the go flat so quickly it doesn't take long) any ideas whats up or do i need new ones?

J