Simplest 2 Battery Setup?

[Seaswirl89]

I recently bought a 89’ seaswirl with a 4.3 OMC engine. Boat came with two batteries but only one battery was hooked up to the boat, seller said second one was for just in case.

I thought that’s great but how does that just in case battery stay charged? The just in case battery looks to be from 2012 so it may not even be good anymore

I’ve done a lot of research over the past few days but there’s some many different way to do a two battery setup. I’m looking for the simplest approach because I have very limited electrical systems knownledge and would prefer not to damage my batteries, the wiring, the alternator, etc. Simplest approach I can think of is leaving the setup as is, buying a trickle charger from Amazon to charge the extra battery 1-2 times a month and keep a Halo jumper pack on the boat in case both batteries are ever dead.

What’s the most straight forward, inexpensive approach to having a backup battery on the boat?

 

[Chris1956]

Buy a battery switch and connect both batteries to it. Set it to both for running so the motor will charge both batteries. When you are stopped and relaxing, set the switch to one battery, saving the other for starting the motor. Easy stuff.

 

[ThomW]

I agree with Chris. Buy a 1/2/both/off battery switch.

This is a very basic idea of the set up. One battery's positive goes to the #1 post on switch, second battery's positive goes to the #2 post on switch. Main power from motor goes to the all or both post on switch. Run a negative wire from battery #1's negative post to # 2 battery's post. then from there to the engine ground. If your boat has a bilge with a float switch, you can run that directly to the battery, so it will work when the boats at dock and switch is off. When you are driving, have switch on both or all, so it charges both batteries. When you stop to fish or hang out, shut off motor and switch the switch to your deep cycle battery. When you wanna leave, switch back to both and start the boat.
Only thing to remember is never switch the switch while the motor is running!

 

[Seaswirl89]

I agree with Chris. Buy a 1/2/both/off battery switch.
View attachment 341109
This is a very basic idea of the set up. One battery's positive goes to the #1 post on switch, second battery's positive goes to the #2 post on switch. Main power from motor goes to the all or both post on switch. Run a negative wire from battery #1's negative post to # 2 battery's post. then from there to the engine ground. If your boat has a bilge with a float switch, you can run that directly to the battery, so it will work when the boats at dock and switch is off. When you are driving, have switch on both or all, so it charges both batteries. When you stop to fish or hang out, shut off motor and switch the switch to your deep cycle battery. When you wanna leave, switch back to both and start the boat.
Only thing to remember is never switch the switch while the motor is running!

Seems easy enough, thank you!

One other question: I’m likely going to buy a new battery because my newest battery is from 2018 and the other is from 2011. I’ll keep the 2018 which is a marine deep cycle (was the battery that controlled the stereo and started the boat) for a back ip battety. Should my new battery be another deep cycle or a dual purpose?

 

[Toyelectroman]

Someone correct me if I am wrong but I was told on a 2 battery setup. You want a starting battery for starting and a deep cycle when the boat is not running but still want to power your electronics

 

[Rabbit929]

I would buy a dual purpose AGM. more expensive than a conventional deep cycle but it doubles as a d/s and a starting battery.
I set my boat up with a blue sea battery switch and charger relay.
the cool thing is, it allows you to charge both any time the motors running, but only draw from 1 when it’s not.
this after much research was the best way to go, as when your motor doesn’t start, you can go flip it to both or battery #2 and start it. constantly switching and babysitting what battery your using and when to switch it would be a pita.
With this setup, forget about it. Just boat along. And if issues arise, switch power to the backup.
Two batteries directly connected to each other can make one bad battery suck down the other, which defeats the purpose of two batteries. You’d be better off with a single large battery really.
Look up a blue sea “add a battery kit” with the charger relay. It basically just allows both to take a charge, but only draw from the selected battery.
the wiring diagram provided makes it pretty easy to do.

 

[crazy charlie]

I recently bought a 89’ seaswirl with a 4.3 OMC engine. Boat came with two batteries but only one battery was hooked up to the boat, seller said second one was for just in case.

I thought that’s great but how does that just in case battery stay charged? The just in case battery looks to be from 2012 so it may not even be good anymore

I’ve done a lot of research over the past few days but there’s some many different way to do a two battery setup. I’m looking for the simplest approach because I have very limited electrical systems knownledge

What’s the most straight forward, inexpensive approach to having a backup battery on the boat?

You got a few great ideas HOWEVER you asked for the simplest approach and that would be to parallel the batteries and add quick disconnect battery terminal to one of the batteries.Simple,cheap ,safe and will only take a few minutes to do.Charlie

 

[poconojoe]

I have the Blue Sea ACR, and yes, it's pretty much install it and forget it. It does the job of keeping both batteries charged.

But, it's not that simple to install. The OP said he wasn't that technically inclined when it came to electrical hookups, so if someone can install it for him, that would be great.
Otherwise a simple 1-2-1+2-off battery switch will do, but require more operator input.

 

[Lowlysubaruguy]

Do you run electronics with the engine off and or have you had any dead battery issues?
if not the simplest way is running them both with no battery isolation or switch ran in what’s called parallel. Thats positive to positive negative to negative this will increase available battery capacity more than double. It will not prevent a dead battery if you leave something on or you have a charging system fault. But its the simplest way. And it works no switches or isolators and less connections to fail.

myself I prefer a dual battery switch its very simple and will come with instructions or there easy to find on the web. Requires two more battery cables and mounting the switch in some cases you’ll need to replace one or both of the original cables if you can’t get your switch mounted in the right spot. This will allow you to charge and run on one or the other or both batteries and to shut them off when you are not using the boat. If you moor your boat the automatic bilge should be hard wired to one of the batteries so it will work. This is reliable except that you have to program your brain to switch battery on both to charge and then to one when your engines off with something on that might drain a battery. If your alternator fails while running what ever batteries are on will also not be charged however many isolation set ups do the same.

I have seen as many expensive isolation system fail as I have just dead batteries, in several cases it was corrosion on the extra wire connections others failed units. My new boat has them and there not easy to get at both are factors that I also don’t like keep them in a place where a visual inspection is done often. I state this after last fall my marine radio stopped working in the worse fog smoke layer that dropped vis to about twenty feet we were fifty miles from shore when it occurred we did not need it but it did not work. I’d like to state connections are always a concern in a boat. The lowrance factory crimped and sealed power wire connector was grown over in corrosion. Keep it simple do a dual battery switch or just run both batteries in parallel.

 

[jhande]

What’s the most straight forward, inexpensive approach to having a backup battery on the boat?

Sounds like you are only interested in a 2nd starting battery. So without all kinds of electronics in the picture I vote for the battery switch and another starting battery. That way while the motor is running you can charge either the starting battery you are using and/or the backup so both batteries will have a good charge.

Depending on how long the boat sits between outings you might want to pickup a battery maintainer to keep them charged while sitting.

 

[poconojoe]

Proper crimping and tinned marine spec wiring are neccessary. Plus, proper gauge wires and correct type and size fuses in marine type fuse holders are also a must.
I use Copper Shield on my connections. It's a bit messy, so all you need is a thin coating.
Clean them bright and shiny and a dab of copper shield or dielectric grease will keep them that way.

 

[Commander_47]

I installed this system on my boat several years ago, and never looked back. It is awesome and does the job superbly.

Blue Sea Systems ADD A BATTERY

Simplifies switching and automates charging for a complete two battery bank solution. The package includes Instructions for 7650 Add-A-Battery

www.iboats.com

This system will keep both batteries charged on an as-needed basis. It isolates your starting battery from the accessories battery. So your radio, lights etc all run off of one battery, and not the starter battery.

If something does go wrong, you can combine both batteries for starting. I have never had anything go wrong.

Despite the maze of wires, it really isn't that hard to install.

 

[Stinnett21]

In my 30 years of bowrlder boating I have never ran down a starting battery. I buy cheap (Walmart, Advance Auto) marine group 24 cranking batteries. Now to be fair I don't run amps or any other electrical accessories. I keep two on board. One connected and one stored unconnected. I never let the newest one (the connected one) get any older than 3 years. I keep the water topped off and the top clean on both. At the start of the 4th season I buy a new one and rotate the old one to the stored location. I have two stored locations on opposite sides of the boat. This allows me to move it to either location, port or starboard, for weight distribution (a 24 weighs around 45 pounds). These days I boat solo a lot. On a solo day I make sure the secondary battery is on the port side countering my weight. I keep both on battery tenders while in storage. My 2 cents.

 

[Commander_47]

I have two stored locations on opposite sides of the boat. This allows me to move it to either location, port or starboard, for weight distribution (a 24 weighs around 45 pounds). I keep both on battery tenders while in storage. My 2 cents.

I agree 100% on the weight distribution. I added an extra shelf on the port side of my engine compartment for the second battery.

My accessories battery is much larger than the starter battery. I have 7 grand kids and we boat a lot. As crazy as it might sound, I have a 26 foot cruiser we often go tubing, water skiing and fishing on.

The accessories battery runs all the 12 volt equipment to include the fresh water pump for the shower and commode, the two sinks, the lights, stereo, trim vanes, bilge pumps, motor lift etc.

I also ran two heavy 12 volt lines to a 110 volt converter under the sink in the front cabin. On overnights I can charge cell phones and electronics, and run the reefer long enough to keep cream, bacon and eggs chilled for morning coffee.

In the picture the big accessories battery is the one port side. The starter is starboard. the fuel tank is port, the waste tank is starboard, and the fresh water tank is under the aft cabin. So it balances nicely.

The batteries are always being charged when the motor is running or when on shore power.

 

[Seaswirl89]

I installed this system on my boat several years ago, and never looked back. It is awesome and does the job superbly.

Blue Sea Systems ADD A BATTERY

Simplifies switching and automates charging for a complete two battery bank solution. The package includes Instructions for 7650 Add-A-Battery

www.iboats.com

This system will keep both batteries charged on an as-needed basis. It isolates your starting battery from the accessories battery. So your radio, lights etc all run off of one battery, and not the starter battery.

If something does go wrong, you can combine both batteries for starting. I have never had anything go wrong.

Despite the maze of wires, it really isn't that hard to install.

I too think that’s the best solution but that seems to be a trickier wire setup. Does anyone have a wiring diagram?

 

[dingbat]

Does anyone have a wiring diagram?

https://d2pyqm2yd3fw2i.cloudfront.net/files/resources/instructions/990310020.pdf

 

[JASinIL2006]

I too think that’s the best solution but that seems to be a trickier wire setup. Does anyone have a wiring diagram?

I added one of these a few years ago, and it really wasn't hard. It did "encourage" me to clean up the boat's wiring, install a proper fuse panel, buss bar, etc., and doing all that was much more fuss than simply adding the kit.

 

[Seaswirl89]

Bare with me, stupid question here…
Attached is a pic of my current setup (boat was setup like this when I bought it). The small red and small black wires are what I believe runs my gauges on the dash, fish finder and radio. The large red and black wires run to the motor. No buss bar. Would it be correct to assume the large black wire would be my ground?

This is a 1989 boat with very few elecaccessories

 

[JASinIL2006]

I would thinks so. Does the other end of the heavy black wire attach to the engine block?

 

[Seaswirl89]

I would thinks so. Does the other end of the heavy black wire attach to the engine block?

From what I can tell, the large black wire from the battery attaches to the engine block behind the starter (finger pointing to where it attaches to the block)