Dual alternators, one regulator?

[maclysaght]

Trying to make sense of my new-to-me boat's electrical system, and planning battery/charger/inverter upgrade. I have two Balmar 110 Amp alternators, that seem to be controlled by one Balmar MC-612 regulator. I have some switches on the control panel that let me switch on the exciter for either or both alternators. Old AGM house batteries are shot, so I will be getting new AGMs. I also have a dedicated SLA starter battery.

I want to update my charging system, so my question is: can I still use one regulator for both alternators? I will have only one house bank (prob 4 AGMs for 850 Amp Hours), and a separate SLA starter battery, which I will charge via a Blue Seas 120 Amp ACR. So I only need the alternators to charge the single house bank.

[smac999]

you should not be using one regulator for 2 alts. the field current is likly to high to run both. I'm surprised you are not blowing regulator fuses running both.

ideally you would have 2. and each alt would have it's own temp sensor.

balmar did make a centerfeilder to run 2 alts at equal outputs but you still needed 2 regulators as well.

[Harmen]

Try to find the wiring diagram for a 72 or 73 Lambo Espada. They used dual alternators. Not sure if I had dual or single regulators....

[maclysaght]

@smac999 Thanks, that was my impression too. But some catamarans I've looked at also have dual alternators (1 per engine), but only one regulator.

There are no temp sensors. Is there any advantage to being able to "switch off" one alternator (or both)? Reduced engine load if I don't need the charge?

[CharlieJ]

OP: The MC 612 is designed to regulate two alternators on a single engine. Is this how your boat is set up?

[tanglewood]

It works fine provided you don't overload the Field output of the Balmar. Just put a clamp meter on when running a single alternator at full output and see what the draw is. I seem to recall that the Balmar regulators can drive 10A. And as Charlie says, the alternators should be on the same engine, and outputs connected to the same battery bank. You will have to pick one alternator for the temp sensor, so if you think one runs hotter, instrument that one. And BTW, the alternators can be different capacities. Each will output the same % of its total capacity based on the field voltage/current. So if the Field is at 50%, a 110A alternator will put out 55A, and a 70A alternator will put out 35A, give or take a bit.


I ran a 190A and a 85A alternator like this for years using an MC624 regulator.

[Bycrick]

Balmar apparently still makes an MC612H which is specifically designed to run 2 alternators on the same engine to a single battery bank.

[EngineerRetired]

Why would you want to replace with AGM batteries again? With a bit of work you can go with Lithium for about the same or even less cost.

[SailingFan]

To momentarily explore the concept, my old Yanmar SB-8 has an alternator, but also has an extra pulley with no belt on it. Can I run another alternator bracket someplace to take advantage of that pulley, and route the result to the house batteries, or maybe to a battery/bank forward that I may have to install for a future windlass? I don't know if the Yanmar would notice the extra drag or not, but it seems that the pulley is just sitting there with nothing to do....?? Am I hauling it around just to have yet another worthless hunk of steel on board? Mods. if this belongs some place else, please ease it over, I just don't know where to put this, and it seems to have some relevance here given we are speaking of dual alternators (though I am speaking of one engine with two alternators going to separate banks, rather than one or two engines with separate alternators going to the same one). I am using flooded acid cell batteries (the big Type 28s from the auto supply store if I recall, not at the boat right now) if that matters.

[misssherry]

You could use the pulley to dual belt a larger alternator. But don't go too large or most of your horsepower will going to the alternator.

[hzcruiser]

Originally Posted by misssherry

You could use the pulley to dual belt a larger alternator. But don't go too large or most of your horsepower will going to the alternator.

Well, since you want a proper regulator, it should not pull down the engine too much. Only because the alt can produce doesn't mean it has to, at all times! You might even think about a max power button for the alt, which you can press when you don't need shaft power.

[Compass790]

We have a YSM 8 that we did run two alternators off so yes you can. BUT, as missherry warns you are limited in how much power you can draw. If you are using to charge at anchor thats fine but trying to motor & run 2 alternators is not going to cut it. We ran a 55 amp & the original 35A but I took the belt off the 35 amp one so it sits as a spare & modified the 55 amp one so I can cut its power output down when we are motoring so as not to overload the puny engine. The Pto shaft is meant to be limited to 1.5hp power draw according to Yanmar..
You can put a switch in the field wire to instantly depower the alternator which we have as well.

[sailingharry]

Originally Posted by maclysaght

can I still use one regulator for both alternators? . . I will only need the alternators to charge the single house bank.

The answer is a resounding yes. I did the exact same thing on my boat, and before I did it I contacted Balmar. I have a pair of alternators that while not identical are similar, around 125 amps each. I checked the field current and they are each around 3.5 amps full current. Balmar said that the regulator is up to the task and their only recommendation would be to increase the regulator power fuse from 10 amps to 15 amps. I've been running two alternators for a year now. As another poster stated, the regulator will adjust percent of field as needed, and this has the effect of adjusting the percent of load on both alternators at the same time.

It is important to note that this option only works if both alternators are feeding the same battery, because the regulator is only looking at one battery to determine charge criteria.

[witzgall]

Chris from Balmar here. The MC-612 Dual is designed to drive the field for two alternators on a single engine charging a single battery bank. It has the additional connectors for the second alternator.
https://balmar.net/product/regulator-mc-612-dual-h/

And the manual: https://www.balmar.net/wp-content/up...For-Review.pdf

[maclysaght]

Lot's to absorb here, thanks. As one person mentioned, since these are already switched, I could have the option to switch off one while motoring to save drag on the engine, or switch both on while running at anchor for more charging. Does this make sense?

Probably stupid question, but several people mentioned field current. Where is that measured? Is this the blue wires, currently with toggle switches from my nav console?

Chris, thanks for the Balmar links. Since I have just the regular MC-612, can that also regulate two alternators? And will this give me the option of using only one at a time, if this makes sense in my question above?