Aduff, if you poke around the web sites from the different equipment makers, you will either get a headache or some good information.<G>
The "automobile" style alternator with an internal regulator is actually not designed to charge batteries, it is designed to taper off quickly so that it does not overcharge batteries when a car is running for hours on the highway. The typical car battery actually only cycles a little bit, not even 5%, as it puts out the starting power and then the alternator takes over.
The external regulators are designed (usually programmable to match your batteries) for large banks and higher rates for sustained periods of charging.
The internal regulators also have no provision for temperature compensation, and that's actually pretty important for batteries. With an external regulator, you really want two thermal sensors. One to the battery bank (or each battery) to monitor battery temperature, and a second which may be internal to monitor the alternator temperature if that's offered. Run an alternator too hard too long, and it overheats and burns out. Charge a battery too hot---and you literally boil the electrolyte internally, which creates air bubbles and impedes the charging. And boils out electrolyte, and eventually melts or warps batteries. And, the charging voltages need to be compensated for temperature.
So while you're looking for "bigger" also look for "better", and ante up for the optional temperature sensors. They make a real difference, long and short term alike.
The "automobile" style alternator with an internal regulator is actually not designed to charge batteries, it is designed to taper off quickly so that it does not overcharge batteries when a car is running for hours on the highway. The typical car battery actually only cycles a little bit, not even 5%, as it puts out the starting power and then the alternator takes over.
The external regulators are designed (usually programmable to match your batteries) for large banks and higher rates for sustained periods of charging.
The internal regulators also have no provision for temperature compensation, and that's actually pretty important for batteries. With an external regulator, you really want two thermal sensors. One to the battery bank (or each battery) to monitor battery temperature, and a second which may be internal to monitor the alternator temperature if that's offered. Run an alternator too hard too long, and it overheats and burns out. Charge a battery too hot---and you literally boil the electrolyte internally, which creates air bubbles and impedes the charging. And boils out electrolyte, and eventually melts or warps batteries. And, the charging voltages need to be compensated for temperature.
So while you're looking for "bigger" also look for "better", and ante up for the optional temperature sensors. They make a real difference, long and short term alike.