Two-switch Battery Scheme

[Rusty123]

As I gradually upgrade my electrical system, I find myself gravitating to a configuration that uses two switches, as shown on the attached sketch.(This is a very simplified sketch, and doesn't reflect bus bars, fuses, charging components, VSR, etc.). From my perspective, this configuration offers the same advantages of the "three on/off switch" configuration, but with only two switches (although one is a 1/2/B/O switch).

Any comments pro or con?

[Stu Jackson]

If it's one of these it's OK. Idea is to not reinvent the wheel. Haven't had time to review it, gotta bring my boat to the yard for some work.

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
1/BOTH/2/OFF Switches Thoughts & Musings - SailboatOwners.com

[goboatingnow]

nothing wrong with what your suggesting. I think the three switch version , will probably work out cheaper and a little easier to understand and operate.

dave

[Jsol]

If you want to go with this setup, consider flipping the switches. So, from Starting Solenoid to ON/OFF. Then connect this Switch to the Common post on the 1/2/Both. Connect your House to 1 and Starter to 2 on the 1/2/Both. Finally connect your DC panel to Common on the 1/2/Both.
This allows you to isolate or combine each bank and allows you to disconnect your Starting solenoid in the event of the starter getting stuck on.
Just another way to go. As I'm sure you will get many suggestions on how to go about this. No wrong way as long as you properly fuse etc.
The links Stu provided are great for understanding pros/cons...

[ontherocks83]

Originally Posted by Jsol

If you want to go with this setup, consider flipping the switches. So, from Starting Solenoid to ON/OFF. Then connect this Switch to the Common post on the 1/2/Both. Connect your House to 1 and Starter to 2 on the 1/2/Both. Finally connect your DC panel to Common on the 1/2/Both.
This allows you to isolate or combine each bank and allows you to disconnect your Starting solenoid in the event of the starter getting stuck on.
Just another way to go. As I'm sure you will get many suggestions on how to go about this. No wrong way as long as you properly fuse etc.
The links Stu provided are great for understanding pros/cons...

+1

if your house bank craps the bed (i.e. has a short and you have to isolate it) you want to start your engine and then be able to switch all house loads to the starting battery so you can fix your house bank without disrupting electrical power to all loads that need it.

[Terra Nova]

Rusty--that will work.

[jstevens]

Looks to me that the only significant capability your 2-switch configuration does not support, that the 3-switch configuration does, is the ability to support all of DC loads from the starter bank. This might be important if the house bank develops an internal short and must be isolated from the charging and load circuits. I don't see how you could support your DC loads in this situation without some re-wiring.

[Terra Nova]

Switching the start battery switch to "both" parallels all batteries.

[CarinaPDX]

I don't see why you don't simply use two "off-1-both-2" switches such that the engine and the house can be independently switched to either bank. I consider it valuable to avoid putting the large starter load on the same battery bank as the boat's electronics.

Greg

[Rusty123]

Originally Posted by CarinaPDX

I don't see why you don't simply use two "off-1-both-2" switches such that the engine and the house can be independently switched to either bank. I consider it valuable to avoid putting the large starter load on the same battery bank as the boat's electronics.

Greg

This is a good point. In fact, my "on/off" switch is actually a 1/2/B/O switch that I've wired as a on/off switch. I could just add a short run of wire to allow house loads (like VHF, for example) to operate off the starting battery in an emergency.

Thanks for all the great feedback.

[jstevens]

"Switching the start battery switch to "both" parallels all batteries."

The point I and a couple of earlier posters were trying to make is that there can be a time when you need to isolate either the start or house bank from both the load and the charging circuits. With your configuration you can isolate the start bank and run everything off the house bank, but I don't see how you can isolate the house bank. Of course that is not a normal occurrence and as long you are prepared to do some temporary re-wiring your configuration should work well.

John

[Stu Jackson]

Originally Posted by Rusty123

This is a good point. In fact, my "on/off" switch is actually a 1/2/B/O switch that I've wired as a on/off switch. I could just add a short run of wire to allow house loads (like VHF, for example) to operate off the starting battery in an emergency.

Thanks for all the great feedback.

Glad to help. One of my links included a "simplistic" diagram, like yours, so check it out.

You can do it all with ONE 12B switch. Not so hard.

But yours is wrong in that it won't let you use the reserve/start bank to handle LIMITED house loads if, as mentioned, you house bank dies, for whatever reason.

KISS, read my links. They show diagrams of just about everything everyone else has said.

[Maine Sail]

Originally Posted by Rusty123

As I gradually upgrade my electrical system, I find myself gravitating to a configuration that uses two switches, as shown on the attached sketch.(This is a very simplified sketch, and doesn't reflect bus bars, fuses, charging components, VSR, etc.). From my perspective, this configuration offers the same advantages of the "three on/off switch" configuration, but with only two switches (although one is a 1/2/B/O switch).

Any comments pro or con?

Rusty,

This will allow dedicated start, start/house from either bank, and 100% isolation of either bank, plus parallel...

[Terra Nova]

Originally Posted by Stu Jackson

...yours is wrong in that it won't let you use the reserve/start bank to handle LIMITED house loads if, as mentioned, you house bank dies, for whatever reason...

Yes, it will.

[Uncle Bob]

Originally Posted by CarinaPDX

I don't see why you don't simply use two "off-1-both-2" switches such that the engine and the house can be independently switched to either bank. I consider it valuable to avoid putting the large starter load on the same battery bank as the boat's electronics.

Greg

+1. That is how I have wired my boat and I find it elegantly simple.