Stupid Battery Set up Question

[kwmeyer13]

My set up has 2 separate on/off switches
port battery starts the port engine and serves as the cabin house supply
starboard battery starts starboard engine and serves as the helm supply

So to keep a long story short, have to replace starboard battery. Would like to change system over to one battery starts both engines and one becomes the house supply.
Here is the stupid question
To do this it is as simple as moving the starboard positive from the starboard on/of switch to the port on/off switch?

I want to switch over the starboard 4D battery to golf cart batteries. The port battery in currently a 4D. There is also a parallel start switch at the helm.

Once again sorry about another stupid battery question thread.

 

[Bacchus]

My $0.02 having just finished a similar project to move my dingle engine start to my thruster batty bank and make my previous start / house battys a pure house bank.
I'd recommend you do some tracing of cables and build a diagram of what you have currently including how both banks are charged from shore charger as well as eng alternators.
Nigel Calders books on boat electrical and mechanical systems are great references and worth investing in before taking on projects like this.
There are multiple ways to accomplish what you are proposing and he outlines several different approaches.
Lastly you might do well to enlist the help of an ABYC marine electrician to help even if you decide / plan on doing the work yourself.

 

[kwmeyer13]

Thanks Bacchus
I do know that my battery charger while on shore power charges each start battery plus the generator start battery and each alternator each charges each start battery.

 

[Bacchus]

Thanks Bacchus
I do know that my battery charger while on shore power charges each start battery plus the generator start battery and each alternator each charges each start battery.

Do you know how those charges get to each of those battys! Which wires / cables carry the start & house loads and charging!
Not trying to be cute just know I thought all I had to do is move the starter cable but ultimately dawned on me that what I was going to do as a first impression would result in one batty / bank not getting charged while running. My alt & shore charger was wired to the batty switch and not directly to the batty.
It helps to put pencil to paper and draw out what you believe you have and then check by tracing.
Also need to consider that house batty cables need fusing / protection but start & alt not normally fused.

 

[O C Diver]

My sight unseen analysis:
Without knowing what engines you have, ideally you want to move the alternator output to what would be the house bank and wire the engine and starter to the other engine battery. Important to understand where the alternator for the house batteries senses voltage. In a perfect world, I would want to add a Balmar external regulator to the alternator charging the house bank.

Ted

 

[kwmeyer13]

Tracing the wires and drawing it up is something that I can do and have done on other systems on my boat so I don’t see that as being an issue. I guess I was looking at the system very simply and thought perhaps it was not an issue just moving the positive from one switch to the other which would leave the everything else in place thus charging each battery just as before. If it’s not that simple then perhaps I will just leave it as is and replace the dead battery but I will get my 22 year old grandson to haul it out.
Thanks for your replies

 

[johnrupp]

In all likelihood you will have to wire the excitation circuit to the alternator through the oil pressure switch on the starboard engine. Most likely in your current configuration each engines key switch closes the excitation circuit for its alternator when in the run position.

 

[bayview]

Why?

Having two completely independent engine systems is IMO the best set up. Golf batteries will start your engine. It usually doesn't take much and you already have a parallel switch.

 

[kwmeyer13]

Why?

Having two completely independent engine systems is IMO the best set up. Golf batteries will start your engine. It usually doesn't take much and you already have a parallel switch.

From everything I have read I was under the impression that golf car batteries were not good as starting batteries.

 

[Dougcole]

I did pretty much exactly what you are considering four or five years ago to our twin engine MS 400. One difference though is that I added and ACR between the two banks. I moved all of the house loads that were on the stb bank to the port bank. I changed the port bank (house) from an 8D to 4 6V golf cart batteries and the stb bank (start) from an 8D to group 31 starting battery. I added a SOC monitor to the house bank.


Both starters (and alternators) go to the stb side. The idea is that they feed the port side through the ACR.




For the most part it works fine, no problem starting the engines and a good long run on the house bank. I'm still sort of unclear on exactly what happens when both engines are running though. I think the alternators may conflict with each other. Both batteries are getting a charge when the engines run so maybe I shouldn't worry about it, but I still wonder.


I think bayview's solution would possibly be better. Put all the house load and the port start load on the port side bank. Start the stb motor from the stb side, and rely on the parallel switch if needed.

 

[kwmeyer13]

I think bayview's solution would possibly be better. Put all the house load and the port start load on the port side bank. Start the stb motor from the stb side, and rely on the parallel switch if needed.

That’s basically what I have.
Starboard bat starts starboard engine and feeds house
Port bat starts port engine and feeds pilothouse
Generator has separate start bat
My battery charger is a 3 bank charger

That is why I thought that if I were to just swap the positive from the port to the starboard it would leave the alternator on the port engine to charge the port bank. I know this is probably as simplistic way of looking at it and from what others have said not really possible.

It’s always been a possible project for me but I never really looked into to very deeply. It just sort of popped up because my port battery crapped out and I need to replace it. If I could just leave the setup as is and series 2 6 volt golf cart batteries then I would but everything I have heard or read leads me to believe that golf cart batteries should not be used as starting batteries.

 

[Tonic1]

Here is what I did...

I also have a twin engine Pilot 34 with the same battery setup. The attached PDF shows a diagram of how i rewired mine. I replaced the 2 8d batteries and the generator battery with 4 GRp 31 AGM batteries with 115 Ah each. They are grouped 3 together for the house bank and one for the start bank for both engines and the generator.

The AC 50A charger and the starboard alternator are connected to the house bank, and the port alternator feeds the start bank. The two banks are connected with an ACR and can also be connected manually with the main switch. I also added a Balmar SG200 for SOC monitoring of the house bank and voltage only monitoring of the start bank.

The main problem I was trying to address is that the 3 bank charger treats all of the banks equally for the 3 step charging profile. With this setup, the generator battery ends up dictating the charge profile, thus starving the 2 larger main engine batteries.

This new setup has been working well for about 4 months, quickly recharging the house bank either from shorepower, or while underway. At the dock you have the full 50A available to the house bank, and underway both 80A alternators are available.

Brett

 

[kwmeyer13]

Great wiring schematic Bret. Thanks for posting.

 

[Bacchus]

Kevin
When talking FLA battys then GCs make ideal deep cycle and GP 31 make ideal starting battys. I have started gassers with a pair of GC and know many others that have as well. While not optimized they can supply plenty of amps for starting... and if you wanted you could always parallel in your other bank for an extra boost.
When talking AGMs its a whole different story. I have confirmed with Eadt Penn that their AGM batty do not have different plate designs and an AGM GC and GP31 both have equal deep cycle and start performance for their ststed specs. That is why they spec both CCA and AH for all of their AGM line.
I'm guessing you aren't interested in swapping to AGM as you should do both banks so your shore charger can be set for AGM. Another way to do it would be to charge one bank on shore power and add a DC to DC charger for the second bank... not as simple as replacing a batty.

 

[kwmeyer13]

Don thank you for all of your time and knowledge. I think to do this the right way will be to just swap out the battery. While I am waiting for the other to die or a significant change in our boating habits occurs I will plan this change over more throughly and know how I am going to proceed before it happens. The most it will cost me till that time is a 4D battery.
Anyone know if there is a good dual purpose FLA 4d battery made?

 

[Bacchus]

Don thank you for all of your time and knowledge. I think to do this the right way will be to just swap out the battery. While I am waiting for the other to die or a significant change in our boating habits occurs I will plan this change over more throughly and know how I am going to proceed before it happens. The most it will cost me till that time is a 4D battery.
Anyone know if there is a good dual purpose FLA 4d battery made?

Sounds like a reasonable plan.
I recently went through a similar decision making / planning exercise and why I had some of that info at hand.
I have a single diesel and Mainship wired their start & house battys as a 2 -8D bank. I also have a dedicated 8D thruster bank. Both are now AGM but I have decided I will not handle another 8D other than to remove these. I wanted a single house bank as I wanted to install a Balmar Smartgauge monitoring system. I decided eng start would be better from my thruster bank and leave my house as a pure house.
Originally I thought I'd go with 4 GCs for house and 2 GP31 for start & thrusters.
When I contacted East Penn they confirmed there was no deep cycle performance advantage w AGM GCs so I plan to go with all GP31 AGMs... 2 for start & 4 for house. That way if any get weak or fail i can better match up the remaining good ones on one or the other bank and only replace one bank. Also if one in my house fails I can eliminate 1 quickly and get by on 3 until I have time to replace thruster battys and swap aged ones into the house.
I only had to add one cable from thruster bank to starter pos and combine existing alt charging cables onto a new power post to charge 2 banks w an ACR.
Good luck w your future mods