WHY Tow Vehicles don't recharge Trailer batteries quickly.

I installed a SIXTY VOLT capacity system on an Arctic Fox (Jesus ...hay ZEUS.. did the work).

Using an EIGHT AWG cable and twenty-nine feet of +positive+ cable length we were able to afford a 37 ampere charge rate with the trailer batteries being at or around 12.1 volts state o charge. The tow vehicle ECU could do whatever it wished

But it did not affect the charging rate one iota.