Dumb Regulated - A dumb regulated alternator does BULK and ABSORPTION and that is it. There is no in-built protection for over heating and they do "burn up" quite frequently when used to drive large banks. If the voltage regulation point is 14.4V it will bring the bank to 14.4V and simply hold it there. If it is below 14.4V the alternator is in BULK mode putting out all it can. A healthy and long absorption charge is actually good for deeply cycled marine batteries and is the part of charging that reconverts lead sulfate.
Super Dumb Regulated - Basically the same as above but they have an additional in-built self protection feature that reduces alternator
regulation voltage based on alternator temperature. These alternators are horrible for deeply cycled batteries because they chronically under charge them and when you lower voltage you also extend charging time. Lowering the regulation voltage has the net outcome of reducing current output thus allowing the alternator to not cook itself. These are cheap automotive alternators using bottom of the barrel cheap regulators and reducing voltage using a temp gradient is the least expensive way to get these alternators through the warranty period. The alternator maker could care less about your batteries.
Certainly with 15+ hour motor runs getting back to full is possible even with a "Super Dumb" alt but this is hours longer than it would take with a dumb or smart regulator..
Smart Regulation - Smart regulators handle the alt differently, in terms of protecting it. The Balmar's, and some other smart regulators, reduce the field (reduce alternator
current output) based on alt temp while the Yanmar / Hitachi reduces the
regulation voltage based on
alternator temp. With smart regulators voltage is not reduced just current output. While this can extend bulk charging time you still get a healthy absorption stage. This type of regulation is much more expensive and thus why
cheap automotive type alternators don't use it..
Absorption voltage is critically important & keeping it at its desired set point for the proper duration means faster & healthier overall charging too. These "voltage gradient" alternators rarely if ever reach the proper absorption voltage and attaining & holding these voltages is absolutely critical for battery health.
The reason the Hitachi charges soooo slow, and you see reductions in current so much, is because the dumb regulator in them is actually dumber than dumb, at least from a "battery charging" perspective......
If you want to protect an alternator, to make it through the warranty period, reducing regulation voltage can work okay. If you actually need to charge batteries, used in deep cycling applications, and do so in a healthy manner the Hitachi's with internal regulation are really quite pathetic. The regulator in them is only about one thing, protecting the alternator from melt downs. It is not about charging performance nor does it care about your batteries. Slap it in a car, where batts are always full, and you're good to go. Put it in a boat with deeply cycled banks and they really perform horribly.
Below is a typical spec sheet for a Yanmar/Hitachi alt:
Note that the regulation voltage is +/- 0.3V which is pretty pathetic but this is what you get from a $1.25 regulator.
If the
design voltage is for 14.4V then you could possibly get one at 14.1V or one at 14.7V. Kind of a luck of the draw kind of specification...
You then subtract the voltage gradient of 0.01V for every degree rise in Celsius above 20C, which is 68F...
You can convert a Hitachi to external but I would strongly suggest setting the Balmar on Belt Manager level 4 and setting the alt temp sensor to temp compensate and reduce field at about 220 degrees if belt manager (formerly called "amp manager") does not cut it. I have seen dozens of burned up Hitachi's that had been converted to external then not set up correctly for alt protection. For example the 80A Hitachi is really only capable of about 45A, in most engine compartments, so as to not exceed about 220F....
