[oil pan 4]

Alternator ratings tend to be optimistic.
To handle 85 amps you would need at least 6 gauge wire, to handle it continously it would need to be 4 gauge.
You will need at least 15 volts to over come wire resistance between the alt and batt if you want to run higher amps.

I have found that car alts typically have about 10 amps available for charging a battery at idle speed.
That alternator is only going to be able to make anywhere near 70 amps is spinning it 7,000rpm.
Even my modified DR44G welding alternator only makes about 25 amps at idle speed externally powering the armature with 13v. The DR44G is a pretty good size medium duty commercial truck alt.