Odd, on this side of the pond the price of batteries has dropped the past year, I just picked up a 12 volt for my Ford pickup from a local supplier for $69US, and the last 6volt that I bought for a GPW was less than the 12 volt by a few pennys. Scrap prices here are in the toilet since the stocke market fall, which is a good thing as scrappers are not out cutting our machinery apart after dark like they were a couple of years ago.
The best batterie I instaled in my 42 GPW had an Everready lable one, and it lived up to the name, I have removed the generator when I replaced the batterie (I do not remember why) and after dropping the new batterie in the jeep, my wife and I hopped in the jeep and drove to meet friends about 70 miles away, we returned after dark and ran with the head lights on the whole way, stopping several time on the way, never having any problem restarting, and the next day, I popped the hood, and found that I had forgotten to reattache the leads to the generator.
Best
Gus