One of the biggest snow jobs in boat gear sales is the myth of the smart three-stage alternator regulator. In fact, the alternator voltage regulators that have been available to us cruisers for about the last 15 years are not that bright...OK, they're downright stupid. They're so stupid that they can't even perform their primary function of charging our batteries properly until full. I know what you're thinking:
John is saying that a piece of gear with tens of thousands of units installed (that's a guess) in boats, and thousands more sold every year, that's so fundamental to comfortable live-aboard life, does not even work. Clearly he has lost his grip.I totally get your scepticism. Heck, when our old, and sadly no longer made, Link 2000-R regulator died—the last cruiser's alternator regulator that was actually smart—I bought the then, and now, most popular "smart three-stage regulator" thinking that it would work, too. I settled down and read the whole manual looking for the fundamental capability that would make it usable on a liveaboard cruising boat, and got to the end to find...nada. So I figured there were pages missing...nope.
What Matters in Alternator RegulatorsWhat's that fundamental capability? The ability to measure when our batteries are full and reduce the voltage output by the alternator to float.
Lead acid (liquid-filled, gel, AGM, whatever) batteries are fully charged when the current (amps) they are accepting at their specified acceptance voltage—typically about 14.4 volts at 70˚F (20˚C)—has dropped to about 0.5% of their total capacity measured in amp hours. (Check with the battery manufacturer, since these two numbers vary between brands, though not by much.)Sounds pretty simple, right? And it is. All you need is a shunt in a cable to the house battery to measure that current—often already there on a cruising boat to support a battery monitor—and a bit of simple logic in the regulator to turn the charge voltage down to float (typically 13.4 volts) when the above threshold is reached, but not before. Easy peasy. But since the death of the Link 2000-R, and a rather complicated regulator from Ample Power (no longer in business), there has been no alternator regulator available, at least that I have found, that could do that simple fundamental thing.
How Could This Be?Why? Beats the crap out of me. Maybe because few boat owners really understand how batteries charge and, even more distressingly, very few technicians in boatyards do, either, so the industry got away with selling stupid regulators for years, and they even had the nerve to call stupid smart—the power of marketing.
Stupid Is As Stupid DoesRather than making that simple required measurement, these stupid regulators guesstimate using a combination of time and how much the regulator needed to juice the alternator field coil to maintain the acceptance voltage. That's bad enough, since different alternators have different relationships between field and output current (amperage) and, of course, how long a battery will take to charge will depend on how much it was discharged...duh.
But wait...it gets worse. These stupid regulators have no way to understand how much of the alternator's output is charging the battery and how much is supplying loads—they truly operate blind.