Two Engines, Two Alternators, Two Banks

[scurvy dog]

sounds simple, right? but i am having my doubts as i am not the smartest guy around. i am installing two beta marine 25 hp diesels, both with high output alternators ( 75 amp, iskra, i think). i also bought two adverc battery management units ( although i may have only needed one, from what i am reading). i want one alternator and adverc to charge one starting battery, which will be used to start both engines ( big battery, small engines). i want the other alternator and adverc to charge a 300 amp bank of house batteries. i have a wiring diagram that will work with a three way battery selection switch ( 1,2,both, blue sea 6007) at each engine. negative will go from house bank to starting battery and to both engines.
the problem is if or when i need to switch the house batteries to start the engines in case the starting battery goes dead. on the initial starting of the engines, both alternators will be charging the same batteries ( both start and house paralleled ) for about 30 seconds until i run below and switch the house bank back to the one alternator. is this okay?? i want to keep it simple.
also, will one 75 amp alternator with an adverc handle a 300 amp bank without overheating or do i have to add a third selector switch at the house bank and make two 150 amp banks instead? thanks

[djmarchand]

There will be no problem with two alternators charging the same bank.

Don't know much about the Adverc regulators. Do they have an alternator temp monitor? If so, no problem. If not, probably no problem either but depends on how often you are recharging significantly depleted house batteries. More often means that the 75 amp alternator is working harder, longer but still probably not critical.

Splitting your house bank isn't wise because you should not charge flooded cell batteries at more than 25% of rated capacity. With a 75 amp alternator charging a 300 amp bank, you are at that limit. AGMs can charge at 50% though.

David

[colemj]

If you want simple, then run both alternator outputs to your house bank and connect the start bank to that with a VSR combiner (Yandina or Blue Seas are examples). Use an On/Off selector switch to bring the house bank to the engines if needed in an emergency. Keep that switch on Off unless needed.

Your plan with the selection switches and needing to remember an operating sequence sounds complicated, less useful, and potentially harmful.

Mark