What many aren’t understanding is this…If you have a Honda Gen, the 15A fuse may be your charging circuit and the 20A for control unit/WiFi, etc.
If your starter pulls 150A, running 60’ using 6ga conductors, the 24VDC would be approx 15VDC at the other end during cranking. You’d have to test it yourself. Then, no buck converter needed for the starter, although you may need one on that 20A circuit going to the ECU. Better yet, just keep a 1A trickle charger on it, keep connections clean and protected from corrosion. Replace battery every 4 years.
Lead acid batteries don’t put out much power below -10F… another issue would be the generator motor oil will be thick in frigid temps… so, the weak battery, combined with the cold generator makes it difficult to start.
I think a heater is needed to solve the issue…
If the generator is so far from the 24V bank, it would need MASSIVE cables to crank a motor over. Likely need over a grand for the wire.
A better solution is to connect a MUCH larger starter battery. As long as it is fully charged, a larger CCA battery will sag less in arctic temps. But at some point, heat will be needed.
Put the generator in a better location, so it can be heated.