This page could be useful Greg ... https://www.electromaax.com/product-...ked-questions/
What about the alternator?
Since the acceptance rate described the maximum rate at which a battery bank can be recharged, it stands to reason that the proper size alternator can only be selected once the acceptance rate has been determined. It is wasted money to charge a battery bank that has an acceptance rate of 70 amps with a 165 amp alternator. Likewise, using a 100 amp alternator to charge a battery bank with an acceptance rate of 240 amps is pointlessly slow and inefficient. The goal is to get the output of your alternator (under actual charging conditions) to match the acceptance rate of your battery bank as closely as possible.
Most alternator manufacturers will provide you with the output curve of the alternator you are considering under hot conditions and at a variety of speeds. An alternator rated at 150 amps will likely only put out 130 amps once it gets hot and will only do that running at full speed. Under realistic charging conditions, you may only be running your engine at 1100 – 1200 RPMs. If your alternator is belted at a 2 to 1 ratio it will be spinning at twice that speed, or 2200 – 2400 rpms then it is quite possible that 150 amp alternator is now only going to putting out 80 amps or so.
Given this, how is it possible to get 200 to 300 amps of real charging capability? Sometimes it isn’t possible, but don’t give up too quickly. Very large alternators with outputs of 200+ amps are now quite common. Additionally, it is often very practical to use two or more alternators simultaneously to charge a single bank. Some boats are already set up to have one alternator charge the engine start battery and a second to charge the house bank. Usually the engine start battery needs little if any charging. An automatic battery bank combiner can be used to allow both alternators to charge the house bank.