Hello all. I have an XB-600 that I added a fifth battery to and wired in after the stock battery box. Everything was runing fine for about 6-8 weeks at about 28mph. Then one day the bike dropped to 20 MPH with all 5 batteries connected. I changed it back to the original 48v 4 battery configuration and got 15 mph so I assumed a battery went bad. I bought a new battery and have replaced each, one at a time, and tested after fully charged and am still running at a much reduced speed. Any thoughts or suggestions would be appreciated, the guys at xtreme want me to send them all my batteries so they can check them for me.