Run on 2 batteries or one

[KandJ72]

Okay so I was able to get my hands on a owners manual for the era of the boat (some revisions are '78) from Carvers archives.
The manual states to run both engines off just one battery, hence always having the other as a spare..... I'm not totally sold on that one. For one having 2 separate charging systems on the same circuit doesn't give me a warm fuzzy, I was having issues with one WAY over charging and that flowing through the whole system just isn't good. I did find the issue and some Genius at one point decided to put in a Chrysler single wire voltage regulator where the Pleasurecraft Ford model used to be . Also there is not a shore charging system onboard either so other then alternating between batteries on cruises there's not a reliable way to ensure charge. I'm planning on running each engine on its own battery for these reasons, if I'm way off I'm open to hearing it and appreciate others advice and knowledge.

[Viper]

The best/proffered way is for each engine to have it's own dedicated battery/bank, and have a separate isolated bank for house loads. All banks must be charged while still keeping each bank isolated so that one system doesn't drain the other. There's a few ways to accomplish that.

If you have two separate batteries/banks and a battery selector switch, unless it's wired a specific way, it's likely it doesn't matter which battery you select, both engines will run off that one battery that you select unless you switch the selector to "ALL" which is not a good idea either. I don't like the selector switches, never did, they cause too many problems, and force the operator to have to think about switch position management which we all know is easily overlooked when out having a good time. With everything else, it's not something you should have to worry or think about.

[KandJ72]

Exactly my thought Viper,
I do have 2 selector switches (OFF/1/Both/2) these are set up Port and Starboard respectively so not only do they select which engine runs of which Batt it also controls 12V accessories for each, Starboard runs the majority. There really isn't a provision for a dedicated "house" battery. My plan is to build a bank of LiFePO4 and add a selector to switch between that and say Batt 2 then not running or on shore power.

[Viper]

If you're talking about adding a lithium bank, you'll have to change all your batteries to lithium once you add a shore charger as they have different charging curve needs compared to regular flooded batteries, and you can only select one charging curve for all banks on a typical charger. Also, if I were to invest that kind of money on lithium batteries, I'd be installing smart alternator charge controllers.

[KandJ72]

I'd use a Victron Orion Tr Smart 12/12 charger for that bank, It will be on an relay that isolates it from all systems once either engine is energized (just as added safety) as well as the manual switch. That provides the CC/CV charge curve they need for proper charging without having to change out everything else. Science has finally caught up

[390Express]

Anyone have a diagram of how batteries should be wired, and how best to use a two (or three, if that is better) switch system?

I currently have two switches, two alternators, four batteries. I believe the "house" batteries are bank 1, and the "start" batteries are bank 2, I say that because the dedicated generator start battery is on bank 2, but each alternator is wired to a corresponding "house" batter, presumably to charge the batteries that died while on the hook, while running.

I generally leave the switch in the engine compartment near the generator to "both", and modify the switch on the deck as needed, 1, 2, both or "off." Is there a better way?

Also, just bought a pronautic 1260p... wire it the same way, or different than the old, junky battery cooker... i mean, charger?

[KandJ72]

So your system is probably very similar to mine. That being the case think of it in different terms, Battery (bank) 1 and Battery (bank) 2. No matter how many are on each for this initial conversation just think of it as 1&2. Best practice is to run each motor off its own battery. Port engine batt 1, starboard engine batt 2. Here's why, you have what's supposed to be 2 totally separate charging systems ( alternators) that don't communicate with each other yet if your switch is set to Both then they are both trying to accomplish the same thing, run your systems and charge your batteries. Now if either battery or 12v system encounters a major defect Both of your charging systems could be compromised. Do people run it that way all the time, yes and I'm sure many have never had an issue doing so. My particular situation was that I had the wrong voltage regulator on my starboard engine when I bought the boat and once I started running it I was seeing voltage on both sides getting upwards of 16+ volts. When I separated batt 1 and 2 to individual engines I could immediately identify where the issue was coming from. Had I stayed on Both it would of potentially fried both charging systems, batteries, gauges, points ( which it did on that engine) and my brand new Garmin Chart plotter!
The way mine is set up from factory is that Port side runs accessories and lights on the fly bridge when turned on to either battery, Starboard runs everything in the living space, lights, fresh water pump, exhaust fan in the head etc. My auto bilge pumps run off battery 1 and fridge runs off battery 2 ( when off shore power) even when switches are off.
My best suggestion is to run each engine on its own while under way then select just one to run off the hook. That way you still have one in reserve to get yourself started if you drain one down by accident.
I can send you a copy of the manual I have it it would be any help.

[390Express]

Source of the post So your system is probably very similar to mine. That being the case think of it in different terms, Battery (bank) 1 and Battery (bank) 2. No matter how many are on each for this initial conversation just think of it as 1&2. Best practice is to run each motor off its own battery. Port engine batt 1, starboard engine batt 2. Here's why, you have what's supposed to be 2 totally separate charging systems ( alternators) that don't communicate with each other yet if your switch is set to Both then they are both trying to accomplish the same thing, run your systems and charge your batteries. Now if either battery or 12v system encounters a major defect Both of your charging systems could be compromised. Do people run it that way all the time, yes and I'm sure many have never had an issue doing so. My particular situation was that I had the wrong voltage regulator on my starboard engine when I bought the boat and once I started running it I was seeing voltage on both sides getting upwards of 16+ volts. When I separated batt 1 and 2 to individual engines I could immediately identify where the issue was coming from. Had I stayed on Both it would of potentially fried both charging systems, batteries, gauges, points ( which it did on that engine) and my brand new Garmin Chart plotter!
The way mine is set up from factory is that Port side runs accessories and lights on the fly bridge when turned on to either battery, Starboard runs everything in the living space, lights, fresh water pump, exhaust fan in the head etc. My auto bilge pumps run off battery 1 and fridge runs off battery 2 ( when off shore power) even when switches are off.
My best suggestion is to run each engine on its own while under way then select just one to run off the hook. That way you still have one in reserve to get yourself started if you drain one down by accident.
I can send you a copy of the manual I have it it would be any help.

Just to be clear, you're suggesting that I remove one of the alternator connections from Bank 1 over to Bank 2, regardless as to which battery in the bank that it is on?

[KandJ72]

No not really, you have one switch for each engine, that switch selects which battery it works off/with. So set one switch to Batt 1 the other to Batt 2. It sounds like you may have the same option for you Genny too, so when running that you can be topping off whichever Battery\Batteries you select. Does than make more sense?

[km1125]

Source of the post Anyone have a diagram of how batteries should be wired, and how best to use a two (or three, if that is better) switch system?

I currently have two switches, two alternators, four batteries. I believe the "house" batteries are bank 1, and the "start" batteries are bank 2, I say that because the dedicated generator start battery is on bank 2, but each alternator is wired to a corresponding "house" batter, presumably to charge the batteries that died while on the hook, while running.

I generally leave the switch in the engine compartment near the generator to "both", and modify the switch on the deck as needed, 1, 2, both or "off." Is there a better way?

Also, just bought a pronautic 1260p... wire it the same way, or different than the old, junky battery cooker... i mean, charger?

You should probably start a new thread with this so that folks don't get confused between your issue/project and the OPs.