Helps if I post this in the correct forum:)
I just picked up a Merida 550 at a yard sale, it was cheap at $50.00. Being a 2002 model and not taken care of by the owner the batteries were shot, even though you could see by the tires the bike only had a few miles on it. Could not get the original 12V 9Ah batteries, but I found some Power Sonic 6V 9Ah batteries that I could stuff in the case. I'm guessing this is a good brand of battery from the information on the internet about them.
Took the bike out for a ride around town and found it to be quite fun, did not seem to add a ton of extra power, but knowing battery technology today did not expect miracles. I do like to modify things though, so I was wondering what are some of the things that people are doing to their bikes.