Sharing a battery ,gen and engine

[Fishsail]

Looking for a simple battery install, I’m thinking of sharing my port engine battery with the generator, separate from the rest of the boat with a large battery. Then have a large battery bank for the stbd. Engine and house bank combined. I’ll have an inverter to run a med sized refrigerator and some outlets while underway so I don’t have to run the genny. Also would have solar to charge the house bank during the day. What is the down side of this? I realize if the gen battery dies I’d have to parallel off stbd side. 42’ with twin Cummins 5.9’s and an 8kw generator.

 

[Iggy]

I am not really up on this topic. I can't wait to read the responses.

The only thing I can think of of that both ALts would be charging the same battery. So what would happen if both are running at the same time? I would think that would not matter. But not sure on that.

And if the genset is also powering the on board charger. So now 3 charging sources on the same battery.

 

[Gdavid]

This should work out fine, if your engines were newer, common rail and dependent on electronic controls for the fueling, there could be a risk of shutting down the port engine when starting the generator, but for a mechanical engine like yours, it shouldn't be any problem.

 

[DavidM]

Your scheme removes one level of starting redundancy but otherwise should work fine.

David

 

[rslifkin]

Sharing an engine and generator battery is generally fine. I do it on my boat. 2 engines and a generator, but only 2 start batteries (generator can be selected to use either one).

I don't like starting an engine from a house bank though (due to voltage dip for electronics, and I consider starting power safety critical, so nothing should draw from it).

 

[tiltrider1]

It will work but it is not a recommended way of doing it. A dedicated generator battery is recommended as a fail safe. The way you have suggested will require a cross over switch between the house and start battery. Should this switch get left on and the batteries drained there would be no way to start the generator to charge the start battery.

 

[O C Diver]

As others have mentioned, it will work, but not optional. In the relative cost of boating, a generator battery is pretty inexpensive and mine usually last about 8 years. Every battery on the boat is hooked to a 120 VAC battery charger and can be recharged by, shore power, generator, or the inverter. Having options is always good.

Ted

 

[fgarriso]

Why don't you install a separate battery on the generator and then one for each main engine. When running each engine will charge its own battery. the generator only needs a small group 24 starting battery. The mains will need group 27 or 32 starting battery. You can then install a house battery bank for the inverter/charger. The generator will charge the house battery with the inverter/charger. You could also install Bomars on the mains to charge the house bank.

With the cost of batterys that is small compared to the other cost in boating.

Ted is doing it the right way just listen to him and do what he says.

 

[Mischief Managed]

I have a small genset battery and one 8D starting battery shared by both main engines. Kinda the same concept you are considering, but even less cost and if you remove a main engine starting battery, you may have room to expand your house bank. I can parallel the house bank to the main start battery or to the genset start battery so there's plenty of redundancy. Since my boat only has 3 banks, my 3 bank 50 amp battery charger takes care of charging everything on its own, though my inverter provides the bulk (150 amp capacity) of the charging to my house bank after draining that bank down.

 

[Iggy]

I have a 8D for a starting battery and a group 24 for the genset. When the time comes, I just may buy two group 31s to replace them both. Right now the two batteries are 2 feet apart. So this would be easy to do.