Battery Cable Help

[Goose]

I've been having trouble keeping my battery charged in my '72 GMC. So, I read the threads on the electrical forum and did the recommended troubleshooting, so far with little success. With the ground battery cable disconnected I was getting a reading of nearly the full voltage of the charged battery. So I think I have found the no Duh! I've been living with, but would like your confirmation. My ground wire from the battery is grounded to the block as required, but there is also a pigtail coming from that cable, much like the positive cable pigtail that goes to the junction box, and it is grounded to the fender. The confirmation I need is there should be no pigtail from the ground cable or at least it shouldn't be attached to anything. Anyway, that is the way I'm reading the wiring schematics. What say you? Thanks.