60 amps is probably higher than the designed add-on accessory load for the vehicle. Assuming it is a diesel the grid heater or glow plugs may also add significant 12v load. You could reduce the issue by not immediately turning on the A/C and running lights etc. Or to add a switch to delay the 60 amp charger until the start batteries are mostly topped up. Best would be to measure or monitor alternator output in extreme load conditions to see actual existing load.
Worst case the alternator quits??? For most people I think it is best to limit these to 20-30 amps.
The documentation should explain the voltage and current requirements to produce 60 amps at 14+ volts. I speculate it may draw 80-90 amps depending on conditions.
If you plan to run this at idle for an extended period I recommend a high idle modification.
