1985 Yamaha G1 Electric Issues

[Automobilist]

My beautiful G1 is not doing well...

Batteries are 2018, and load test ok with my $18 Harbor Freight tester. Each battery individually tested. Each showing about ~6v. Total bank output just under 36v (35.6v)

Digital voltmeter on dashboard used to read up to 36v, now doesn't get higher than 30.2v when charging. Cart drives slowly, but any incline stops it.

Tested the original (old) Lester charger, it seems to be putting out between 35-36v. The visible fuse on the charger looks and tests ok. However, the ampmeter on the charger does not move up when plugged in like it used to. I noticed this about the same time the cart seemed to be really losing power up hills. Plugged in to outlet & cart, timer on, no amp meter indication. Used to go about halfway up generally when starting charging.

All cables seem intact and solid.

Appreciate input, solutions, cause, etc.