The number and arrangement of battery cables on 4 6 volt batteries can be very confusing if you failed to identify the arrangement before your even start removing the cables. I took a picture of mine after I wrapped a piece of red electrical tape on the end of every cable going to a positive terminal. Even after doing all of that, I left off one important positive cable and because of it, I couldn't charge the batteries off the engine alternator. Quick look at the digital picture and I found the missing cable hiden behind the batteries.