[QUOTE=DotDun;546061][QUOTE=skipmac;545976]First, a proper, smart regulator will not shorten the life of a battery. In fact I believe data shows that a well charged battery will outlive a constantly undercharged battery.
A smart regulator matched with the wrong size alternator (too large) will infact shorten the life of a battery. Under charging a battery is simply a symptom of not charging long enough, nobody has advocated not charging the battery to full. A smart regulator doesn't know the charge rate, only the battery voltage and the amount of time the charge is applied. It then uses it's internal knowledge of the battery type (as you programmed it) and makes a decision on how much voltage to apply to the field of the alternator. No magic.
You can always create a screwball system that will fry batteries, or any other part of a system. I am posting
comments based on the assumption of a properly designed and installed system, not screwed up, badly designed system. I am assuming the OP is not interested in that kind of charging setup.
So, again assuming a proper system, you will
charge batteries faster with a larger alternator and smart regulator and without damage. Using a standard automotive alternator/regulator system it would be almost impossible to fully charge a battery due to the tapering off of the charge as the battery charge state increases, battery voltage increase and the internal resistance of the battery increases. Unless motoring for hours you will never fully charge a battery with an automotive regulator and to put many amps back into a large, deep cycle battery will take hours of engine
time, especially with a 65 amp alternator.
A smart regulator will pump a lot of amps into a very low battery to bring it up to a much higher percentage of charge in a much shorter time. Much less wear and tear on the engine
A smart regulator particularly with battery temp sensors will also reduce charge to a rate that will not damage the battery as it reaches a fuller state of charge.
Also a smart regulator will include an equalization
feature that will allow max topoff of the battery and reduce sulfation when you can run the engine long enough which is acknowledged to increase battery life.
And even if you don't agree with all the above you have to admit that a smaller, dumb alternator/regulator will take much longer to charge a battery, all other things being equal. So it still comes down to, do you prefer to wear out a $20,000 engine or maybe
reduce the usable life of a $200 battery.
That math seems pretty plain to me.