What is better two batteries with an isolator or a high amp alternator?

Answer 1

Until an auto battery expert revises this answer, it will be generic in nature, and very much a matter of opinion in any case. For more than one reason, I suspect that two batteries with an isolator would be more dependable than only a single battery with a high output alternator. 1. Two batteries provide redundancy in case one were to fail. 2. Except for battery charging, an alternator, either normal size or high capacity, has no other function, and provides no beneficial service. And during cranking, a high amp alternator puts out NO MORE CURRENT than a normal alternator. So, if there is no increased current output during cranking, the excess current output of a larger alternator is just an exercise in futility. 3. Two batteries, if properly connected are capable of providing up to double the starting current, compared to only one. This allows for more dependabiliy in the event of engine deficencies which result in difficult starting. Note that a properly tuned engine [electrical, ignition, and fuel systems] will start on the first crank without the need for additional current that would be provided by a second battery.