They have a 120amp alternator for these?! Wow! I want one, especially if it has an internal regulator that puts out 14.5volts. But honestly how much of a load are you putting on an alternator with single starting battery? Are you charging a secondary bank or running an inverter? The glow plugs are no more than 50 but that’s intermittent. 120amps seems excessive unless you have 60 amp Continuous load. I doubt you could get a small starting battery to accept an 80 amp load for more than 30 seconds unless it were completely flat or it’s lithium.