Edward
You have many errors of battery capacity values; charging current and battery voltage.
I have seen small tractors with 12V and 150 AH batteries and larger ones such as the D8K and D8N from Caterpillar with 2 batteries of 12V and 200AH each.
As you say it is 900A, I would ask to be 900AH, but you should be sure of the voltage, because it could be 36V or more.
The starting chargers, I have seen one of 200A, of 12; 18; 24 and 36V in high and low.
Regards