Originally Posted by powercat_ras
The starter cable for the generator is tied to the coach battery side of the 12 volt system in the chassis electrical box. The starter will want to draw well over 70 amps DC.
I've contacted Onan directly to get the starter draw on their 4kW generator. The official answer was 280 amps. I've actually monitored the draw, during warm weather, and it was 180-190 amps using lithium batteries (slightly higher voltage than lead acid). Add cold weather, heavier weight oil and lead acid batteries and you are looking at the potential of well over 200 amps. Length of cables and size will also be a factor.
If the generator doesn't turn over, aside from a defective starter, you are looking at corroded starter cable connections or batteries that aren't as "charged" as you may think. Battery voltage measurements can be misleading. Monitor the voltage under load only for a truer reading on battery capacity, voltage AND amps equals power.