Two Alternators and Two Battery Banks On My Boat

[@ianmac86]

Thanks Jeff. Really liked and appreciated your detailed explanation on this issue. Cheers

[@rico2207]

Good talk..would be better with diagram and schematics..

[@edthornton5148]

Hi, similar question I have a 50 year old twin engine boat with 2 battery banks. Starboard engine charges an 8D starting battery which is used to start both engines. The port engine charges the house bank. No guesses as I was involved with the rewiring to make it happen. (previous setup had the port engine being started from the house bank which I didn't like). My question is about replacing the existing tired house bank which is currently comprised of 4 golf cart batteries. I'd like to increase the capacity of the house bank and have room in the battery box for up to 6 golf cart or some other technology. Other info - I have 295 watts of solar connected with a 40 amp mppt controller, a 40 amp charger and a Victron battery monitor. There is no inverter charger on board. Simplest solution would be to replace all with 6 flooded golf carts but would like a more maintenance free option. Ideas? If I went with lithium or AGM batteries would I need to change the charging methodology?

[@gretchendancarlson3148]

how about a how to no this set up

[@Ibian666]

Hypothetically, assuming both alternators output similar voltage, how about putting them in parallel? Wire them both to the start battery and combine it with the house batteries through a voltage sensing relay. This way the full output of both alternators are being used instead of a lot of it just going to waste.

[@nazimkhan3497]

hi i have a shrimp boat with 2 banks of 24v. my engine bank is charged with the main engine alternator and the house bank is charged with an alternator on an aux engine. how do i charge my engine bank with the aux engine alternator and vice versa?

[@svStargate]

I recently crewed on a 41 Fontain Pajot cat where the house bank was charged only by the port engine’s starting battery through an ACR. after watching lots of your videos you got me into “redundancy “ and didn’t feel safe with this set up on this boat. Is it ok to add another ACR from house connected to starboard engine’s battery and have it disconnected with a switch so it can be used for emergency in case of a problem with the pot engine’s alt? Or better yet, what can I use to charge the house with both engines at same time?

[@PacificYachtSystems]

Good one... yep, you can definitely have both port and stbd batteries connected to house battery via battery combiners and even manual parallel switch.

[@toobglued]

@@PacificYachtSystems but what about the alternators "fighting" each other or cycling on / off .

[@toobglued]

nothing wrong with having the ability to switch over to the other alternator but personally, I would use one or the other to charge the house but not both alternators at the same time.

[@ralph9987]

Thanks Jeff. Please help with clarifying this proposal I have heard some boat owners do. With an existing bank of maybe 4-500 AH of AGMs, there have been suggestions of placing a second bank of Litiums in parallel to it. The lithiums are maybe only 100 or 200AH in capacity but are meant to supplement the AGMs due to the voltage difference at the same SOC. This is all assuming that the AGMs are being charged by the alternator, solar,wind, shore power and the Lithiums are being charged via a DC 2 DC charger from the AGMs. Could you please help me work out if this is a viable way to go about this please and if you could include a discussion about how to best go about installing a 1,2,both battery switch. Thanks again for this great series.😁⛵

[@PacificYachtSystems]

Good one, but unfortunately never seen this deployment in person and much less done an installation like it. Can anyone with this setup share the pros and cons of their setup.

[@tomryan7979]

Thanks for your great informative videos. This is a question that might interest your subscribers! I have a twin a engine boat (24V system with external regulators, original to the boat 1977) with 3 battery banks each engine charges its own battery and the house bank is charged using a smartbank relay system which connects all batteries, if it sees a charge (also has victron multiplus for shore power charging). my question is how can I get both alternators to put out equal amps as the port alternator always puts out 25 amps while the starboard alternator puts out very little. Both altenators while old work perfectly because both output 25 amps if only one engine running .

[@PacificYachtSystems]

Tom, great question. I believe the Balmar centerfield addresses your concern of balancing two alternators with external regulators.