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1/BOTH/2/OFF Switches Thoughts & Musings

Gunni

.
Mar 16, 2010
5,943
Beneteau 411 Oceanis Annapolis
@Jackdaw: Placing both house and engine switch in the on position combines the battery banks. I'm not clear why you would do that when you can switch off a dead/damaged battery and power from the good bank. See attached.
 

Attachments

Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
@Jackdaw: Placing both house and engine switch in the on position combines the battery banks. I'm not clear why you would do that when you can switch off a dead/damaged battery and power from the good bank. See attached.
No it does not. The engine battery is wired to one switch and its output goes to the starter. The house bank goes to the house switch and then to the DC panel. The crossover switch is wired to use either battery bank for starting or house loads without combining.
 
Nov 8, 2010
10,812
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
I never liked the default Beneteau wiring. While it allows battery isolation, it does not provide for a dedicated starter battery. Run your house (default switch position) down, and all the switching in the world will not start your diesel.

Re-wiring that switch as an 'emergency' gives you the exact same setup as in Maine's diagram; built in bank isolation with the ability to power both house and starter with either bank with the other one off. It protects you from both internal shorts and dead banks.
 

Gunni

.
Mar 16, 2010
5,943
Beneteau 411 Oceanis Annapolis
I never liked the default Beneteau wiring. While it allows battery isolation, it does not provide for a dedicated starter battery. Run your house (default switch position) down, and all the switching in the world will not start your diesel.
Sure it does, I have used it. (see diagram). You keep your engine battery switch off (dedicated). Run your house down to where it won't start the battery? SWITCH IT OFF. Switch on your dedicated engine battery and zoom zoom. Never combine a dead battery with a good battery - the dead battery sucks up the juice.
The engine battery is wired to one switch and its output goes to the starter. The house bank goes to the house switch and then to the DC panel.
The engine and house banks are wired together on the load side of the switch. You can use either bank to run house or engine loads.
 

weinie

.
Sep 6, 2010
1,298
Jeanneau 349 port washington, ny
I have the same wiring on my Jeanneau (same parent company as benes).
The house goes to the house bank and the engine to the engine battery.
There is a combiner factory installed which allows the alternator to charge both but otherwise, the two circuits are completely separate.
20160614_183618.jpg

I kept the negative switch as is and instead added a 'jumper' red cable connecting the load sides of both the house and engine banks with an on/off switch in the middle. It was just easier than re-routing all the negative wires to single bus.
The effect is the same. I can run the house off the house bank and the engine off the engine bank. Should either one of those fail, I can run the engine off the house bank and the house off the engine bank. (Or I could combine both banks, not that I would ever want to do this).

(the white wire in the pic is my solar which is connected to the house bank via the controller mounted just on top of the balmar smartgauge. Once or twice a year I manually switch the lead to the engine battery just to top it off, like just before winter storage)
 
Last edited:
Nov 8, 2010
10,812
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
Gunni,

OK I see what you are saying, but two issues for me that make the other scheme better:

1) You don't ever really know the status of your dedicated starter battery until you try and use it and it does not start.

2) The pulse/surge when starting the diesel with the house resets half of my electronics, and makes the AP go wacky.
 

Gunni

.
Mar 16, 2010
5,943
Beneteau 411 Oceanis Annapolis
1) Both of my banks have a digital volt meter. My dedicated engine start batt sits disconnected and fully charged until needed.
2) I had that problem with my old house battery bank in the waning days of it's life. While it often showed good voltage, it had no amp capacity. Turning on the starter caused the voltage to my electronics to dive.

My 8 year old Group 24 AGM engine start battery has been a good pick for the job, no water, no maintenance, always at 100% SOC.
 
Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
I have the same wiring on my Jeanneau (same parent company as benes).
There is a combiner factory installed which allows the alternator to charge both but otherwise, the two circuits are completely separate.

(the white wire in the pic is my solar which is connected to the house bank via the controller mounted just on top of the balmar smartgauge. Once or twice a year I manually switch the lead to the engine battery just to top it off, like just before winter storage)
With a combiner you should never have to lead the solar output to the engine battery. The combiner doesn't care where the voltage is coming from and should combine with solar output as well as the alternator output - or any other charging source.
 
Nov 8, 2010
10,812
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
1) Both of my banks have a digital volt meter. My dedicated engine start batt sits disconnected and fully charged until needed.
2) I had that problem with my old house battery bank in the waning days of it's life. While it often showed good voltage, it had no amp capacity. Turning on the starter caused the voltage to my electronics to dive.

My 8 year old Group 24 AGM engine start battery has been a good pick for the job, no water, no maintenance, always at 100% SOC.

Not trying to change your mind. ;^)

Just pointing out how you can use the three switches to easily create a system exactly like Maine's diagram by simply re-wiring them.
 

weinie

.
Sep 6, 2010
1,298
Jeanneau 349 port washington, ny
With a combiner you should never have to lead the solar output to the engine battery. The combiner doesn't care where the voltage is coming from and should combine with solar output as well as the alternator output - or any other charging source.
I know. It's just not really necessary for what I do. The few minutes of engine running I do, mostly replenishes what gets depleted during the engine start... like my car. I mainly just like to top off that battery before and after winter to keep it healthy.
 

Johnb

.
Jan 22, 2008
1,130
Hunter 37-cutter Richmond CA
No it does not. The engine battery is wired to one switch and its output goes to the starter. The house bank goes to the house switch and then to the DC panel. The crossover switch is wired to use either battery bank for starting or house loads without combining.
Take another look at the diagram.
 
May 17, 2004
2,177
Beneteau Oceanis 37 LE Havre de Grace
Sure it does, I have used it. (see diagram). You keep your engine battery switch off (dedicated). Run your house down to where it won't start the battery? SWITCH IT OFF. Switch on your dedicated engine battery and zoom zoom. Never combine a dead battery with a good battery - the dead battery sucks up the juice.
The engine and house banks are wired together on the load side of the switch. You can use either bank to run house or engine loads.
Beneteau has changed this in later models. Our 2014 does not have the engine and house banks tied together. They have isolators to split the alternator charging but otherwise the banks are separate. See the attached diagrams - one from the manual and one I sketched from what I saw.

IMG_0270.JPG


IMG_0271.JPG
 

Gunni

.
Mar 16, 2010
5,943
Beneteau 411 Oceanis Annapolis
Just pointing out how you can use the three switches to easily create a system exactly like Maine's diagram by simply re-wiring them.
I like having a ground disconnect as Beneteau designed; saves me the trouble of winter storage battery cable disconnections. But yeah, MaineSail has forgotten more about boat electrics than I will ever know. Wish he would move to Naptown!
 

Gunni

.
Mar 16, 2010
5,943
Beneteau 411 Oceanis Annapolis
Beneteau has changed this in later models. Our 2014 does not have the engine and house banks tied together.
Wait a minute, you have a bow thruster and a third battery bank on a 37 foot boat? If I had to maintain 3 battery banks I would want some way to be able to use that extra lead I'm giving a ride - to start my engine or power my instruments when the Kimchi hit the fan.
 
May 17, 2004
2,177
Beneteau Oceanis 37 LE Havre de Grace
Wait a minute, you have a bow thruster and a third battery bank on a 37 foot boat?
Sure do. Although the third "bank" is just a single group 27 AGM, so not much maintenance required. I suspect they do that because otherwise powering the thruster from batteries 20' away in the aft cabin would take seriously big cables. I agree that it would be good to have more emergency cross over options given the amount of wasted redundancy. We carry jumper cables just in case, but I've considered repurposing the ground switch as a more elegant cross over solution. Probably something I'll get around to after the first time one of those batteries goes dead in a pinch.
 
Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
Take another look at the diagram.
I have worked on a few Beneteaus and they were wired with independent banks and a switched negative. I agree with Jack that re-purposing the negative switch as a emergency crossover does what Mainesail has suggested many times.

As far as the diagram - which one?

Gunni's link in post 201 doesn't work.
 

Johnb

.
Jan 22, 2008
1,130
Hunter 37-cutter Richmond CA
I have worked on a few Beneteaus and they were wired with independent banks and a switched negative. I agree with Jack that re-purposing the negative switch as a emergency crossover does what Mainesail has suggested many times.

As far as the diagram - which one?

Gunni's link in post 201 doesn't work.
I have re posted the diagram
 

Attachments

Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
Works for me, at least as a download on my phone
I managed to download the pdf. Strange arrangement and not like the Beneteaus I have been on. But with the switches already there it is easy to arrange the 3 switches as start, house, and crossover to do as Jack has suggested. It creates the simplest most reliable arrangement in my opinion - one anyone can understand.