Car won't start - HONDA?

if you already saw mechanics then I would assume they have checked the battery terminals and made sure the connectors are tight and not corroded. I would probably try testing with a wire (or volt meter if you have one... would be safer) at various points... get an insulated wire (like speaker wire) and hold one end to the metal part of the positive connector and then touch it someplace on the frame and see if you get a spark. then follow it to the other side and do the same... if you get a spark on the first side but not the second there is obviously a break in the wire. If it tests good on both sides then try replacing the negative.