Hi Joe, I´ve had my 1979 CX500 since it was new, but have had it in storage for over 10 years. The battery is behind one of the side covers, I don´t remember which. Also it seems like I had the side covers off when I opened the seat. I believe I needed a 10mm wrench. Good Luck - I´m hoping to get some time to fix mine up in the next year or so.