Two alternators, two banks, one acr

My current set up is twin engines with a single 4D to start both motors, a single house bank comprised of 4 6V GC batteries in series/parallel with a blue seas ACR between the banks. Both alternators go from their starter to the start bank. The house bank is charged through the ACR.


I had an electrician on board last week to help me with some work and he didn't like this wiring set up, but didn't have a suggestion as to the best way to do it. He's a young/apprentice type guy (he works for me on weekends on the side, he's a good kid) and is going to speak to his boss about the best options.


How would you guys set up the wiring? I like the batteries as they are.



Thanks.

In general, I like your setup.
One change I would make is to charge the house batteries directly with the alternators and put the ACR between the house bank and the start bank. This significantly reduces the current that has to flow through the ACR (because obviously you need much less current to charge the starter than the house batteries). I would be curious to know which bank your battery charger is hooked up to (from your shore power inlet).

Are the alternators externally regulated? If not, the potential concern is that one of them gets 'lazy' and puts out less current than the other because their outputs are directly linked. That said, I have the two alternators linked on my boat and they do fine, one might be 10 amps less than the other at any given point.

Thanks Westiculo.


I have three leads on my shore power charger, a pro mariner 50 amp. One leg each goes to the house bank, start bank and genset start battery.


The concern my electrician had was that the alternators would get "confused." They are not externally regulated.


I've had this set up for 5 years. The only possible issue I have had is that my house bank committed suicide after only 4 1/2 years, despite me treating it pretty well. I keep it on the charger all the time at the dock, and never let it get below 60%. I'm religious about keeping the water up.


He thought maybe the dual alternators over charged it.

Internally regulated alternators do fine if all they are doing is recharging what current is used to start the engine, but aren't great dealing with a house bank. Rather than cooking the house bank, this set up probably bled them to death by undercharging and sulphation.

Typically the ACR goes to the house bank first, so if it were me, I'd do the following.

1. Rewire the ACR so all charge current goes to the house bank first, then motor and genset start second.
2. Install a smart regulator like the Balmar 612.
3. Install a Balmar SG200 monitor so you can know what is going on with the state of your batteries.

You might find some wiring options here:. https://www.bluesea.com/resources/170/Battery_Management_Wiring_Schematics_for_Typical_Applications

I have a similar setup, but my alternators both charge the house bank with an ACR to charge the start batteries. My alternators have external Balmer voltage regulators that are controlled by a Balmar Centerfielder that coordinates the alternators' charging. I've used this setup for 10 years and it has worked well.

Since you've probably got the alternator charge run through your start cables, I'd suggest the same as Delfin above with the following change.

Move your starter cable for one engine to the house bank so that alternator will charge the house bank when running. Yes, it means you're starting one side with the house but the charge is immediately replaced and you can still start both with the start battery with the proper switch/cables or jumper cables.

This way one alternator will charge the house bank and one will charge the start batt. I agree with an external regulator for the house side alternator. I'd also consider an upgraded alternator output to the 100A range for better charging.

With this setup, your ACR will be there for shared charges when needed but the normal configuration will provide charge to all batts under normal conditions. If an alternator fails, you can still provide the charge to both banks through the ACR.

Mine is set up as I described but my alternators are not providing a charge through my start cables. I recabled them directly from the alternators to their respective bank. This way, all loads and charges are handled independently. In other words, I can share a single charge source between 2 batts without affecting the selected loads and I can share loads on a single battery bank without affecting the charges.

I would have one battery(s) bank to start both engines and the alternator from one engine to charge it. I would replace the other engine alternator with a commercial grade 250 +/- amp truck alternator with an external 3 stage regulator tied to the house bank. My preference on alternators in the application is Leece Neville. They're designed fire trucks and emergency equipment that sit running at low RPM for hours putting out full amperage. This will do a very nice job of recharging your house bank. For redundancy, install a high amp battery switch to tie the 2 banks positive leads together (negatives should already be tied together). In the event of either a dead battery bank or alternator, combining both systems through the battery switch, will get you going again. This is a very simple system, that should be extremely reliable, without the need for a bunch of electronic devices other than the external 3 stage regulator.

Ted

I’m set up exactly like Ted suggests. It’s simple, redundant and keeps the two systems separate unless one battery bank is dead.

I agree with your electrician. I'm a big fan of using an ACR to charge the engine battery.

I have my alternator, battery charger and solar panel all charging the house bank and just the VCR charging the start battery. Simple and reliable.

I tend to be a little less concerned by others about one alternator getting lazy. In my thinking, one alternator will almost certainly saturate before the other. But, by the time that happens, it happens because the batteries are almost charged anyway. So, if it takes a little longer to get the last bit because only one alternator is working, I, personally, am not worried about it. I'm also not worried if the wear is uneven between the two alternators.

I, personally, would be more worried if only one of them was going to to be working during a period of time when the demand was larger and it was really needed.

My boat's present set-up, which was reworked with existing parts from how it was when I bought it, has one 4D start battery per engine, one 4D start battery for the generator, and 2x4D batteries used for house and windlass.

Switches for each engine can parallel the start battery with the house or use it, instead. The house can also be disconnected as can the generator start battery.

There is a 3-bank AC charger that charges the start batteries (2x engine + 1x genset) and an inverter charger that charges the house.

"Normal" mode for me has the batteries charging from the generator or shore power via the AC chargers. If I am not going to run the generator, I need to remember to parallel the house with the start batteries before getting underway (can't move those switches while underway, they aren't make-before-break) so they charge from the alternator.

There is also a solar charger that is tied to the house. It can keep it topped off for light use. If not using the boat for an extended time on hook, e.g. a mooring or anchor, the house batteries can be paralleled with the engine start batteries to keep them all float charged. Of course, one battery could then take the rest with it.

I have 3 sets of bilge pumps, one tied to each battery, with the "low pump" (the only one that should /ever/ be used tied to the house battery. The other two would be increasingly bad days -- but come off the other batteries in case the reason for the bad day is a bad, isolated, house battery.

The generator doesn't float charge, but has very little parasitic load -- only its own controller. So, in theory, it'll be a long time before it runs down. And, I wanted it isolated so I could use jumper cables from to bootstrap it if I good up and empty everything else.

gkesden, if you like the idea of self supporting genset and start battery,consider a dedicated solar panel with basic regulator. Unless connected to a battery charger, it only gets charge from its own alternator,when run. Works for me.

Hi BruceK,

I like that idea! There would be real value in adding a panel or two so I could float the start batteries separate from the house batteries.

But, I always try to look at my flavor of boating before doing things like that. In reality, don't really leave the boat that long without having AC power, either from the genset or shorepower. When I'm cruising I usually run the genset for 30-45 min nightly, usually while cooking -- it puts a load on it, makes dinner, heats the hot water back up, and tops off the batteries. Maybe heats/cools/dehumidifies the boat a bit.

Given where I am now with this boat, and how I tend to boat, the most impactful electrical change I could make for me would probably be to go from 2x4D house batteries to 4x4D (or equivalent) house batteries. I'd love to be a sailboater one day, both in boat and boating style. But, for now, well, I've got plenty of diesel aboard to burn. I'd have added those batteries already, but I'm still learning where I want them based upon where I tend to crawl to reach things, etc.

In my last boat, I didn't have solar power at all. Between the shore and the genset, I was basically set. I always wanted it "in case" I ever left it for an extended time at a mooring -- but that was never the case.

When I bought this boat, I upgraded some things to meet the way I used the boat, e.g. added a bigger charger and an inverter/charger; fixed some things to be more code compliant, e.g. added battery boxes (moving things to make room), protected all loads, etc; and reorganized things to better suit my use.

With respect to the reorganization, the boat seemed to "originally" have 2x4d batteries for each engine and 2x4D batteries shared by the generator windlass, and house, with the PV system tied to the gen/house/windlass. But, by the time I got the boat, one house/genset/windlass battery had been removed -- and the other had blown up, because the PV controller was set up to charge at 14.7V in all modes, e.g. float (guess = that's what happened to the removed house battery).

As I mentioned, I was going to add more batteries. But, I just couldn't get happy with where to put them. Just by adding the battery boxes space got impossibly tight and I had to relocate the genset battery from where it had been (near house and engine start batteries) to its present location (aft of generator).

At any rate, I've got two large PV panels right now, wired in parallel, and going to a single controller. Eventually, I may look at separating them and adding a controller so I could, as you suggest, have one panel for house and the other for engines. Maybe I could add a panel -- but that would likely involve sacrificing space I want for something else.

I feel like it is more likely that I'd just add a small flexible panel in the little bit of space I have above the bimini to float charge (and only float charge) the start batteries, leaving the big one to handle the house+windlass, and only the house+windlass.

But, even that is pretty distant priority. There are so many other project on my list before that, from upgrading electronics to new carpeting to adding an oven, to putting the controls which had been removed back on the lower helm, to putting on some doors that had been taken down, to...

...guess that's why they call it a priority list

Cheers!
-Greg

Ted, John,

I like your setups and the simplicity. The only thing I'd want to do differently would be to add a switch so that instead of just being able to parallel the house and the start, I could do that -- but disconnect the start leaving just the house. That way, if there were to be a problem with the start battery that was a current sink, the house can still start the engines.

Of course...you're probably using the simple and reliably approach to that, too...and would just pull the wire on the bad start battery in the tremendously unlikely case that should happen.

gkesden said:

Ted, John,

I like your setups and the simplicity. The only thing I'd want to do differently would be to add a switch so that instead of just being able to parallel the house and the start, I could do that -- but disconnect the start leaving just the house. That way, if there were to be a problem with the start battery that was a current sink, the house can still start the engines.

Of course...you're probably using the simple and reliably approach to that, too...and would just pull the wire on the bad start battery in the tremendously unlikely case that should happen.

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You answered your own question. I would pull the battery cable off the negative terminal. Pretty easy, and the negative eliminates the risk of shorting the system out.

Ted

O C Diver said:

I would have one battery(s) bank to start both engines and the alternator from one engine to charge it. I would replace the other engine alternator with a commercial grade 250 +/- amp truck alternator with an external 3 stage regulator tied to the house bank. My preference on alternators in the application is Leece Neville. They're designed fire trucks and emergency equipment that sit running at low RPM for hours putting out full amperage. This will do a very nice job of recharging your house bank. For redundancy, install a high amp battery switch to tie the 2 banks positive leads together (negatives should already be tied together). In the event of either a dead battery bank or alternator, combining both systems through the battery switch, will get you going again. This is a very simple system, that should be extremely reliable, without the need for a bunch of electronic devices other than the external 3 stage regulator.

Ted

Click to expand...

Thanks Ted,


What kind of voltage regulator do you use?

Dougcole said:

Thanks Ted,
What kind of voltage regulator do you use?

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I have a Sterling 4 step voltage regulator. It works very well for me, but there are 3 or 4 companies that make external regulators. Their remote display was disappointing and unnecessary. A SOC (state of charge) gauge will tell you more than their display, and is a very useful instrument.

Ted

O C Diver said:

I have a Sterling 4 step voltage regulator. It works very well for me, but there are 3 or 4 companies that make external regulators. Their remote display was disappointing and unnecessary. A SOC (state of charge) gauge will tell you more than their display, and is a very useful instrument.

Ted

Click to expand...

Thanks. I have a SOC monitor, I (ironically) installed it just before my house bank died. It's kind of a good thing, I guess, in that I set it up with a brand new bank, so it should be more accurate as to AH used/remaining, at least for the next year or so.


Balmar is not in my budget, so I'm looking around for other options.


For summer cruising, which is mostly what we do, we tend to run the genset about 6 hours per day for air conditioning, so I haven't had issues keeping my batteries up. I'm more concerned that my alternator set up could have damaged the bank.


Still seems to me that I should have gotten longer out of it given the demands I placed on it.

Dougcole said:

Thanks. I have a SOC monitor, I (ironically) installed it just before my house bank died. It's kind of a good thing, I guess, in that I set it up with a brand new bank, so it should be more accurate as to AH used/remaining, at least for the next year or so.


Balmar is not in my budget, so I'm looking around for other options.


For summer cruising, which is mostly what we do, we tend to run the genset about 6 hours per day for air conditioning, so I haven't had issues keeping my batteries up. I'm more concerned that my alternator set up could have damaged the bank.


Still seems to me that I should have gotten longer out of it given the demands I placed on it.

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Well you can always set your banks and wiring up now, and upgrade the alternator and external regulator at a later date.

Ted

Would it be a good idea to wire one of the alternators directly to the house bank, and keep both starters wired to the start bank?

Dougcole said:

Would it be a good idea to wire one of the alternators directly to the house bank, and keep both starters wired to the start bank?

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That's the way I would do it. The only issues to determine are where the alternator senses voltage, and how it's turned on. A single wire alternator senses voltage from the battery bank. A multi wire alternator may sense voltage through one of the smaller gauge wires. Depending on how many wires go to the alternator, it will either be turned on by the ignition switch or it may be self exciting when the alternator is spinning. If you use the Sterling external regulator, it will have a wire you connect to the ignition switch and another wire that senses voltage which you would connect to the house bank.

Ted

In my opinion yes. That is how I’m set up. Start bank starts both engines and is charged from port alternator. Starboard alternator charges house bank.

Dougcole said:

Would it be a good idea to wire one of the alternators directly to the house bank, and keep both starters wired to the start bank?

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IMO, not much point. The amount of charging required to top up a start battery is next to nothing. The ACR will combine charge sources whichever battery is in "first" position as soon as that battery reaches the trip voltage. I guess it's a question of whether you want your twin alternators to spend 2 minutes charging the starter bank, then paralleling the house bank or vice versa. Generally, the house bank is recommended to be "first" since its charging requirements are so much greater than the starter bank.