nolton
Living Legend
my guess would also be the main cables at the battery.
the way the batteries r made there is not much depth for the bolt so it is possible that the bolt would be tight and the cable connector be loose.
i am big on volt meters i would put the pos lead on the bat cable and neg lead on the ground (earth) side then hit the starter button to c what happens.
i am guessing that u will loose most of the voltage. with the starter button held in move the probes to the lead posts to see if there is still 12 volts.
with the starter button held in if u have 12 volts on battery posts and almost none on cables then the connection is bad.
Thanks ill try that too.