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My experience is mostly with outboard engines on the various boats I own or have owned and have often used an outboard engine's auxiliary charging circuit to keep a house battery charged.
Do any inboard engines have this same kind of auxiliary circuit, or is house battery charging (with an inboard engine) dependent on a combiner setup or other kind of onboard battery charger?
__________________ Captain Ethan Maass Sea Tow South Shore M a s s a c h u s e t t s
Serving Cape Cod Bay and offshore
My experience is mostly with outboard engines on the various boats I own or have owned and have often used an outboard engine's auxiliary charging circuit to keep a house battery charged.
Do any inboard engines have this same kind of auxiliary circuit, or is house battery charging (with an inboard engine) dependent on a combiner setup or other kind of onboard battery charger?
My boat uses a combiner to keep the starting and house batteries charged. There is no auxilliary charging circuit.
My experience is mostly with outboard engines on the various boats I own or have owned and have often used an outboard engine's auxiliary charging circuit to keep a house battery charged.
Do any inboard engines have this same kind of auxiliary circuit, or is house battery charging (with an inboard engine) dependent on a combiner setup or other kind of onboard battery charger?
Typically, an inboard engine has an alternator very much like a car alternator. It makes (whatever) amount of power and there is only one output. If the alternator makes enough power, it make a lot of sense to use a combiner to charge more than one bank. If the alternator doesn't make enough power for the boat's needs, there are plenty of sources of higher powered Marine alternators. (Including West Marine)
Cruisers who spend nights at anchor and don't want to be running a generator, and thus need a fairly substantial house bank, often replace their engine's stock alternator with one meant for more heavy-duty use.
Such an alternator can put out more amps for much longer than typical stock alternators (which, being designed primarily to quickly recharge starting batteries, can overheat if run hard for very long).
They also typically need an external regulator, which knows how to charge a big house bank properly (stock alternatos with built-in regulators generally don't). Once these two items are installed and correctly set up to replace the stock alternator, they work like a charm. They take great care of the house bank, which can last many years of not drained overly deeply.
Charging house bank and starting bank properly can be done with a simple 1-both-2-off switch, or more automatically with a combiner, also known as VSR or ACR. We use the switch. Switch to starting bank to start, keep it there for 10-20 minutes until starting bank is recharged thoroughly, then switch back to house bank and leave it there until the next start.
__________________ Richard Cook
New Moon (Bounty 257)
"Cruising in a Big Way"
I've never seen an aux output on an inboard like some outboards have. That doens't mean they don't exist, because I'm no expert on inboard setups. But I've never seen or herd of one.
The easiest, safest and failproof thing to do is install the appropriate battery switch/combiner cluster like the BEP units. Easy to install, even easier to use.
Great information and great suggestions. I use the BEP clusters with voltage sensing relays on two of my (outboard) boats already, so will probably also use them if/when I operate an inboard boat as well.
Thanks for making this one of those threads where people can learn something!
__________________ Captain Ethan Maass Sea Tow South Shore M a s s a c h u s e t t s
Serving Cape Cod Bay and offshore
RCook has given you the juice. One other thing; on some large inboards, I have seen a second alternator mounted. This obviously depends on the holes/pulleys available at the front of the engine, etc. I think that normally the single large capacity alternator with external regulator will be the better/easier choice.
RCook has given you the juice. One other thing; on some large inboards, I have seen a second alternator mounted. This obviously depends on the holes/pulleys available at the front of the engine, etc. I think that normally the single large capacity alternator with external regulator will be the better/easier choice.
My owner's manual states that if I have the optional four battery house bank I will have a second alternator on the other side of the engine. I have the four battery house bank but only a single alternator. I never bothered to check the rating. I will today if I remember. It hasn't been a problem for me yet.
Lots of good information above. There are alternators which have dual output circuits; Balmar is one manufactuer who makes the dual output. High output alternators need two belts, and thus a different pully system off the front engine pulley.
I would use a combiner--it is cheaper and easier than a dual output or adding a second alternator.
On our long distance cruising boats, we had several battery banks, with one main bank of 1200 amps, and just used battery switches for charging. This worked fine for many years and over 100,000 miles.
Charging house battery with inboard engine 
