Where does the negative battery cable connect to?

[rovercanus]

There is a ground strap on the engine on the back of the block on the drivers side. Make sure this didn't burn through when you tried to start it with out the cable attached.
What happens when you loose a connection like that is the electrickery will try to find another path to ground. In all likelyhood, whatever it found is burned through. You may want to check your fusible links also.

 

[pilot13]

battery - frame - frame - starter.

per experience if your voltage becomes lower than normal make sure you have a good contact between frame and starter, if you have some oil drips(very common) things will become loose.