Help with battery switch

[Wassim Merhebi]

I just received my boat after a 2 year wait twin outboard 290 SDX . It came with a single on/off battery switch unlike my previous twin engined boats that had 1,2,1+2 settings . This would drain all batteries if I’m out in the water for several hours . Spoke to the dealer so they’re proposing to install an additional two switches , one for each engine (I would have a total of 3 switches) . I found this unusual but they said if they install the switch I mentioned above the alternator wouldn’t charge the Home battery anymore . Has anyone come across such a situation? And do you know how long I can use the home battery (no fridge) by using the lights and music only ? Thanks

 

[Byron]

Look into a voltage sensitive relay by BEP

 

[Little Ducky]

Find another mechanic.

If they can't figure out how to add the correct switch to include your house battery get someone else to hook it up for you.

How many batteries does your boat currently have? 3?

 

[Skybolt]

I just received my boat after a 2 year wait twin outboard 290 SDX . It came with a single on/off battery switch unlike my previous twin engined boats that had 1,2,1+2 settings . This would drain all batteries if I’m out in the water for several hours . Spoke to the dealer so they’re proposing to install an additional two switches , one for each engine (I would have a total of 3 switches) . I found this unusual but they said if they install the switch I mentioned above the alternator wouldn’t charge the Home battery anymore . Has anyone come across such a situation? And do you know how long I can use the home battery (no fridge) by using the lights and music only ? Thanks

They are correct in that two engines will not charge three batteries if a three battery isolator is not installed. The bat switch you described is not the correct way to charge three batteries. But is for switching out the one in use when an isolator is also being used.

How are you intending to connect the batteries? One for each engine and one as a house battery? Or shared engine battery?

 

[Wassim Merhebi]

Thanks for your input . The boat came with 3 batteries , 1 for each engine and the house battery . They sent me the wiring diagram claiming this is recommended by Mercury , it shows the engine batteries have an isolator each but the house battery doesn’t

 

[Skybolt]

Thanks for your input . The boat came with 3 batteries , 1 for each engine and the house battery . They sent me the wiring diagram claiming this is recommended by Mercury , it shows the engine batteries have an isolator each but the house battery doesn’t
View attachment 140477
View attachment 140476

The battery isolator (#6) on each engine charges the it's battery and the house battery. The isolator is probably a charging ACR given both isolators are connected to the house battery.

If that is your batter architecture schematic then I don't understand what the issue is?

Do you have three battery switches?
Do you have a battery charger and is it on when the boat is not in use?

Not really sure what your shop wants to do. But you should have a switch for each battery installed. And if the boat isn't wired as that schematic depicts then it should be. With all three switches on and the isolators working, all three batteries should be charging.

Now, if there isn't a battery charger running when your not using the boat, then possibly the engine run time isn't sufficient to keep the batteries topped off.

EDIT: If your isolators are not ACR's then that is something that could be upgraded. They may help with the batteries dying quickly.

https://www.bluesea.com/support/articles/1366/Automatic_Charging_Relay_[ACR]_Explained

 

[Lazy Daze]

To add onto what Sky said... the house battery DOES have an isolator. Each battery doesn't need it's own isolator. The isolator(s) are shared by the engine's cranking battery and the house battery. I think that's where you're getting confused? If you follow the charging output from each engine, you can see how the charge can be split to go to either the cranking battery or the house battery.

Also, your switches don't factor into whether or not the house battery is being charged... other than, of course, the engine switches need to be on to operate the engines. BUT... if the engines are running, the house battery is being charged. You can verify this with a voltmeter.

This is assuming your setup is as you posted.

Maybe you just didn't find where the other switches are located?

 

[Wassim Merhebi]

Thanks everyone for your input

 

[ttmott]

The battery isolator (#6) on each engine charges the it's battery and the house battery. The isolator is probably a charging ACR given both isolators are connected to the house battery.

If that is your batter architecture schematic then I don't understand what the issue is?

Do you have three battery switches?
Do you have a battery charger and is it on when the boat is not in use?

Not really sure what your shop wants to do. But you should have a switch for each battery installed. And if the boat isn't wired as that schematic depicts then it should be. With all three switches on and the isolators working, all three batteries should be charging.

Now, if there isn't a battery charger running when your not using the boat, then possibly the engine run time isn't sufficient to keep the batteries topped off.

EDIT: If your isolators are not ACR's then that is something that could be upgraded. They may help with the batteries dying quickly.

https://www.bluesea.com/support/articles/1366/Automatic_Charging_Relay_[ACR]_Explained

The newer SR boats are using ACR's with manual overrides. I think pretty much everyone has gotten away from the diode based isolators due to the voltage drop issue.
Even though a bit on the complicated side to host a single house battery the system shown on the drawing @Wassim Merhebi illustrates is sound. I wouldn't change a thing other than stand up a larger house bank. My only advice is - stay on top of the corrosion prevention on all of those connections.