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artbyjody 06-09-2008 01:09 PM

Installing a Automatic Battery Selector Switch
If there was one gripe I did have when I finally started using my new Barberis, was that there was no easy access to the battery switch. It was under the nav table and impossible to see which mode it was selected to without getting on my hands and knees and hoping I do not bang my head on the table after I was done.

So, it was obvious to me that the first item in the electrical upgrade process would be a new switch. Blue Sea Systems sells a battery switch that is three positions but includes a automatic combiner / surge suppressor. The automatic part means that one doesn't have to switch to "combined" mode on the selector if the starter battery is low - it automatically switches over house banks to the starting circuits.

Installation is not difficult but can be a challenge for someone not quite sure where or what the wires currently on their Guest or Perko battery switches are. So, I figured I would share my tips on how I tackled the problem.

1. Turn off all power on both AC / DC side. This means pull out your shore power cable, and if possible disconnect leads from your batteries.

2. Undo the holding screws for your current switch so that you can pull out the original to actually handle it. Do not start disconnecting the cables on the back.

3. Your switch most likely will have three terminals on the back. You will want to label each wire with the position number that corresponds to the terminal / switch position. In this document I label the "off" terminal as #0, swith position #1 as #1, and the third as #2. I also drew a circle and annotated where the wire originated at. I used painters tape and a marker to annotate each.

This step is the most important because there is no one to one matching to the Blue Sea selector terminals. Once properly labeled then do one terminal at a time and remove the retaining nuts and cables from each terminal.

Pause and reflect:

You now will have the opportunity to place the switch in a new location or into the old position. Note, that you may have to improvise a mounting solution if you do not drill a new hole. The Blue Sea selector was smaller in circumference than the Guest one I replaced. I opted for drilling a new spot myself, moving the selector to a slightly more accessible spot. A Light now goes where the old one was.

But before going all gung ho. Ask yourself, will the current cables reach the new spot? You may have to extend the current ones for the new location will mean a trip to the store to get matching gauge wire for the project. It will be cheaper in most cases to just keep it where it is...and once installed you may find you never touch the selector switch ever again.

Possible additional items you will need prior to starting the actual re-wiring:
  • Large Bus Bar (4 terminals minimum) for tying in the ground (I advise this strongly). Most boats simply tie everything to the negative lead of the associated battery. The bus bar will allow for a common ground for all systems. ($60-90)
  • Small Bus bar for connecting "always live" circuits such as bilge pumps, memory for stereo, etc...($26-50)
  • Additional battery cables to handle the new configuration of wiring. I used automotive battery cables myself as the marine versions were 2X the price.
The Blue Sea Switch has four poles. the right side is grouped as #1 consisting of top and bottom terminals. In my installation this was for the starting / motor aspect. Side #2 consists also of top and bottom terminals and this is your housing side.

Attaching the Charger Circuits:

Odds are you have a charging system when connected to shore power to keep the batteries charged. On your old system, you probably had one attached to the #0 (for house battery) and a second one attached to #1 (for starting battery).

The charging cable attached to #0 on the old one will go to the top terminal #2 of the Blue Sea Switch. This is the house side.

The charging cable attached to #1 on the old one will go to the top terminal of #1 of the Blue Sea Switch. This is the starting side.

Attaching the house circuits

Connect up your house circuit wires (that run to your circuit panels) to the top terminal on #2 side of the Blue Sea System switch. In cases where you have more wires than will fit, you can use a bus bar, and run one lead from the terminal post to the bus bar. Remember to also install a protective cover over the bus per ABYC as it is a live circuit.

Attaching the Alternator:

The Alternator wire will go to the bottom post of #2.

Attaching the Starter:

Starter wire goes to top post of #1.

Before adding the Battery Cables:

Now is time to install the Automatic Charging Relay (ACR). Note that you want a decent location for this as the wires have to run underneath it. Also beware you need to install fuseable links inline, although I will admit I did not as of yet. They are not included with the system.

Mount the ACR in a suitable location - near the battery switch if possible - but enough distance that you can bend battery cables. Connect the Start Battery POSITIVE to the B terminal of the ACR.

Now connect the house battery terminal to your Selector by adding it to the bottom post of #2. Take another battery cable and attach it to the same post and run it to post A on the ACR. There is no need to run a separate cable from the house banks as the terminal post on the selector will do the same function just fine. You will also connect up any of the battery / metering sensing wires for the house battery to this post.

Now take a battery cable and from the POSITIVE terminal on the starter battery - connect it bottom post of #1. If you have a battery / metering sensing wire for battery gauge - attach here as well.

NOTE: The battery sensing wire can also be placed alternatively on the top posts for #1 or #2 sides of the Selector. Doing so will mean that the selector has to be ON to have the gauges read battery levels. That is how I have it arranged versus using the bottom posts.

Now install the negative terminal post. Please, make sure you get the large size one, its pricey all things considered but required. Attach all the battery, house circuit, and any other negative / grounding cables and secure them.

Now install the starting circuit wire the the appropriate terminal on the ACR, ground, led...

Double check the tightening of posts and nuts. Go back over how you installed it correct any issues you may find. Install any protective covers, secure battery etc.. The system should now be set-up.

To verify your system install. With the Selector OFF - turn on shore power, and turn on your battery charger if it is not hardwired with a circuit breaker. Using a voltage meter - measure the voltage output at the top terminals of both #1 and #2 of the battery switch. You should read 13.5 volts or so.

If you can turn off your battery charger do so. Now turn selector to ON. repeat the same.

Test starting the motor and go through your DC circuits and verify proper operation.

Hope this write-up helps someone else tackle this upgrade. It really is not difficult - just takes some patience and maybe a few runs to the store to get various cables and the likes...

lbdavis 06-09-2008 01:15 PM

Nice one Jody. I have decided to go this route - thanks in large part to your persuasion after my stupidity this weekend. I'll pull this back up in the fall when I'm done sailing for the year.

I'd give you a rep point but it's not important anymore! :) :) :)

sailingdog 06-09-2008 05:37 PM

For bus bars, I prefer these:

A bit more convenient and takes care of both needs, as well as has a cover for ABYC compliance.

Birdface 06-15-2008 08:09 PM

And recommended wire gauges for these connections?

artbyjody 06-16-2008 02:14 AM

Depends on the run - the Blue Sea instructions will have distance versus gauge wire you should use.. or check their website. It will vary based upon your locations of panels to selector switch and batteries to selector switch. So, I can't recommend a particular gauge.

sailingdog 06-16-2008 06:40 AM

BTW, the switch Jody has posted a photo of in his OP has FOUR POSTS on the back. It is designed to switch the house and starting batteries on simultaneously, and isolate the house and starting loads unless it is in the combine position.

wchevron 06-16-2008 12:47 PM

thanks for the run down. i was debating on installing one of these when i rebuild my elec. panel next winter. you've probably saved me countless hours of retracing all of my new wiring wondering why my batteries won't work and cursing Blue Sea for coming up with this new fangaled technology.

Birdface 07-07-2008 09:35 PM

I'll be attempting this sometime this week.

I went with 4 guage wire between the batteries and charger.... hopefully it wasn't overkill, it cost an arm and a leg.

brak 07-07-2008 09:38 PM

depends on the distance.
Here is my own calculator for wire gauge based on amps and distance: AWG by wire length/amps calculator

artbyjody 07-07-2008 09:38 PM


Originally Posted by Birdface (Post 338145)
I'll be attempting this sometime this week.

I went with 4 guage wire between the batteries and charger.... hopefully it wasn't overkill, it cost an arm and a leg.

Nothing is truly overkill - I think that is probably the typical gauge used for most runs ...but, yes - its expensive! Good luck on the project :)

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