Alternator Regulator

[btrayfors]

Best way to optimize charging from an alternator is with a smart battery regulator (e.g., Balmar MC-612 or 614). But, in your case, it's not likely to be much of an improvement PROVIDED that the internal regulator in the alternator is set high enough (at least 14.4; 14.6 or 14.8 even better).

Some older alternators are set much lower, and the battery not only charges more slowly but never gets a full charge.

Bill

[djmarchand]

"Do you know what the voltage at the battery bank is when you are reading only 20A from that 80A alternator?"

Yes, I do. It is about 13.5V which is what most internally regulated alternators are set at. That is the point. Internal regulators, regulate VOLTAGE, not CURRENT. So once the battery reaches about 75% SOC then 13.5 V isn't high enough to push more than about 20 amps into a 440 AH battery bank.

Without messing with the internals of the alternator, all you are going to get out if it is that 13.5 V. That is where the theory of the Sterling device comes into play. It fools the alternator into thinking the batteries it is hooked to is very discharged (well below the 75% SOC) by presenting a low impedence. That way the alternator will produce a lot of amps at 13.5V. It then converts the 13.5V into the 14.5 or so it takes to drive lots of amps into the battery.

The theory sounds good. But I wanted someone who really used one to report on what it would really do.

David

[mitiempo]

Internally regulated alternators used to be set at about 13.8 volts - several decades ago. Now the normal setting is 14.4 volts.

13.5 is either very old or has an issue - you are correct that charging at that voltage is very slow. My Hitachi alternator, at least 25 years old, outputs 14.4 from its internal regulator when the batteries are down a ways. It has not been modified.

An alternator will not charge faster with an external regulator as long as the set voltage is the same. If you compare an old alt set at 13.8 with an external reg set at 14.4 the external will charge faster. But if both are set at 14.4 there is no time gain with external. You do gain a float stage as well as options such as temp sensors for batteries and/or alternator as well as the ability to limit alt output for longer life with some external regs like the Balmar MC-612.

[GordMay]

Originally Posted by djmarchand

... The standard Yanmar alternator (made by Hitachi) has an internal regulator, so it is not possible without modifications to bypass that regulator*...

... buy a high output alternator. These have heavier windings and better cooling to deal with the high current output.

* Installing a diode in series with the Sense wire will "fool" the internal regulator into thinking the battery voltage is about 0.6 volts lower than it actually is.

See also ➥ http://kb-kbh.dk/shipslib/el_ombord/...ndbook_ocr.pdf

[djmarchand]

mitiempo:

I am just guessing, but these charge controllers could present a low impedence to the alternator, even though the battery needs 14+ V to charge rapidly. This low impedence "fools" the alternator to think it is charging into a deeply discharged battery. The alternator voltage may be as low as 12V but the voltage that the controller sends to the battery is 14+V. Sort of like a reverse solar charge controller.

Just a guess. That is why I would like to hear from someone who has really used one and has some data.

Daid

[amarf]

if it really works that way it is quite interesting. At the end of the day it does not metter if it works one or another day as long as results are there...I'm very interested in hearing if someone tried it in real life situation.

[btrayfors]

I've not had a chance to examine or test one, either. But, from the technical description I believe David is correct, i.e., the circuitry is probably based on a DC-to-DC step-up converter.

These circuits are often found on boats, from the smaller ones used with, e.g., radios to larger and quite expensive ones designed to provide 13.8VDC to a host of electronics when the actual battery voltage is 12VDC or below.

Cute, and smart! HOWEVER, at a discount price in the U.S. of over $400 for the 80A version, I wonder if it makes really good sense. For that money, you can buy a really good external regulator (e.g., MC-612 or MC-614) and have some $$$ left over to put toward a much larger alternator.

IMHO, this would be preferable for those with large battery banks and, particularly, those with AGMs or gels which can put quite a strain on a small alternator. I'd much rather have a big alternator fully capable of putting out a lot of amps for a long time even when hot, rather than depend on an alternator temp sensor to keep my AGMs from burning up my small alternator being goosed by a tricky DC-to-DC converter :-)

JMO,

Bill

[CharlieJ]

Post #22
+1

Charlie