Visit our Popular Forums

SVMC fc25 · 10-01-2019, 05:24 PM

Please bear with me. Relative Newbie here. We have a 2019 FC25 RBQ that we have had for about a year. I am trying to figure out where and how I should install a battery disconnect switch and i haven't figured out how to search to find that topic. So I am hoping someone can point me to a link that explains how to install a disconnect switch. A link with a wiring diagram would be very helpful. I'm pretty good with general electrical stuff, but there must be something about the dual battery setup that I don't understand.
Thanks for your help.

Steve

Mollysdad · 10-01-2019, 05:32 PM

A bit on the "overkill" side, but I love my disconnect.
https://www.airforums.com/forums/blo...sconnect-3036/
(blogs are limited to 10 photos, I might redo it as a post so I can add more.)

SVMC fc25 · 10-01-2019, 05:45 PM

Mollysdad,
Thanks for the reply. Unfortunately when I click on your blog link I go to a page that says invalid blog link.
Steve

uncle_bob · 10-01-2019, 06:06 PM

Hi

There are a nearly infinite number of ways to do a disconnect.

First question - disconnect the + or the - or both?

There is no real benefit to disconnecting both. You can disconnect the + or the - and get the same benefit. Whatever is easiest is going to work pretty much just as well as the other approach.

Next up - disconnect what?

All wires leading away from the chosen side of the batteries need to go through the switch. That generally includes a bit wire to the inverter and another wire to the rest of the trailer. If you do the positive, there may be a wire to the solar pre-wire and the electric jack (if you have one).

The wires interconnecting the two batteries do not need to be played with.

Next - is this true for all setups?

Well, no. If you have modified your trailer that could lead to other perturbations in all this. If you are talking about a motorhome with chassis and house batteries, that's different as well.

How much switch do you need?

If you have a stock inverter, the switch needs to be rated for at least 150A. If you don't have an inverter a 50A switch might be fine. Given that Blue Sea switches are dirt cheap and rated for way more current than you need, there isn't a lot to worry about here.

How can you do it?

There are the cheap / simple Blue Sea rotary switches.

There are the battery post mount disconnects

There are the Blue Sea solenoids.

Each has it's pluses, simple answer is to go with the <$20 switch and move on if you want to do this quick.

So what to do:

1) Get a switch

2) Get a hunk of copper wire with lugs on it

3) Pull the wires off the negative side of the battery.

4) Hook them to one side of the switch

5) Run the other side of the switch back to the battery with the cable.

6) Mount the switch somewhere

That's about it.

Bob

daleyocum · 10-01-2019, 06:41 PM

Like Bob said, there are lots of ways to do this. If you want something easy that you could do in an hour, the battery post units like he mentioned are hard to beat.

**wulfraat** · 10-01-2019, 09:38 PM

Here is some more info... 2-way or 4-way blue sea switch. Mount inside or outside of the battery box.

SVMC fc25 · 10-02-2019, 10:06 AM

Bob,
Thanks for the detailed reply. What I was missing was the need to connect all of the negative (in my case) leads attached to either negative post (other than the battery to battery connectors) to the switch. Does it matter which negative post the lead back from the post connects to?
Steve

SVMC fc25 · 10-02-2019, 10:10 AM

Wulfraat,
Thanks for the pictures and diagrams. They help a lot. Do you remember what gauge wire you used for the lead that runs back to to the battery post?
Steve

SVMC fc25 · 10-02-2019, 10:14 AM

daleyocum,

Thanks for the picture. When you use the battery post unit, do you install one on each of the negative posts of the batteries? or do you feed all of the leads (positive or negative) to one battery post switch?
Do you know where to get a battery post switch?

Steve

Mollysdad · 10-02-2019, 10:46 AM

Quote:

Originally Posted by SVMC fc25

Mollysdad,
Thanks for the reply. Unfortunately when I click on your blog link I go to a page that says invalid blog link.
Steve

That's odd. I click on it and it goes. Maybe only I can see it?

With two batteries, Airstream has them in Parallel - pos to pos and neg to neg. Then they divide the loads between the batteries.
What you'll need to do is to consolidate all the positive sources on one battery and all the negatives on the OTHER battery. Then put your disconnect on the main positive OR negative.
I switched the negative side because those cables were longer, no splicing.

I also made jumpers just long enough to allow checking the water

Gleverett · 10-02-2019, 11:40 AM

Quote:

Originally Posted by daleyocum

Like Bob said, there are lots of ways to do this. If you want something easy that you could do in an hour, the battery post units like he mentioned are hard to beat.

I installed the one mentioned above over a year ago on the negative main line at the battery post. It works great. I just unscrew the knob, check my propane alarm inside the trailer to see no power going to it. I've left my trailer for months with the disconnect engaged and the batteries were strong when I turned them back on. 2015 FC rear bed twin.

daleyocum · 10-02-2019, 04:17 PM

Quote:

Originally Posted by SVMC fc25

daleyocum,

Thanks for the picture. When you use the battery post unit, do you install one on each of the negative posts of the batteries? or do you feed all of the leads (positive or negative) to one battery post switch?
Do you know where to get a battery post switch?

Steve

You just install the post switch on the negative battery post that all the wires are connected to. The switch goes on the post and then all the wires go on the output of that switch. Those switches can be found on Amazon . There are variants of that kind of switch also on Amazon. Search there for "Battery disconnect switch."n For example, if you aren't using the posts, you might prefer this switch.

**wulfraat** · 10-02-2019, 07:45 PM

Quote:

Originally Posted by SVMC fc2;

Wulfraat,
Thanks for the pictures and diagrams. They help a lot. Do you remember what gauge wire you used for the lead that runs back to to the battery post?
Steve

1/0 gauge.

uncle_bob · 10-03-2019, 08:42 AM

Hi

This is not something that is Airstream specific. Pretty much any RV shop can do this for you and get it done right. Cost should not be too crazy.

Bob

Landozoor · 10-03-2019, 10:37 AM

Hellooo…

To disconnect my batteries, I made this diagram.

With a bipolar battery switch.

This allows not to have a current feedback from a battery in cable when you disconnect the other.

I found this switch in UK.

https://www.autoelectricsupplies.co....04/category/30

There must be a similar one in the USA.

Also. I mounted fuses on the battery terminals.

For the positioning of the battery switch, I wanted the shortest cable.
But also the most accessible command.
So I made a rod to go to the front of the electrical panel.

daleyocum · 10-03-2019, 12:59 PM

Interesting. I guess I was assuming the OP had two six volt batteries in series or a single 12v but should have asked. In those cases no fancy switch would be necessary.

Most people, even with parallel 12v batteries, don’t go to the trouble of one of those DPST switches. I wonder in practice how much difference it makes especially if the batteries are both the same capacity and age.

Mollysdad · 10-03-2019, 01:12 PM

Since the inverter and converter come to the battery box on separate lines, I always though it made sense to switch them off separately.
I considered two of those "Red Key" switches mounted on the box.
The problem with the terminal post switch is some cables are on posts, some are on studs, and putting all together is a wad.
What you want to avoid is switching off one battery, when the goal was to switch off the loads.

daleyocum · 10-03-2019, 06:43 PM

The BlueSea switches are the way to go for those with an interest in doing the fabrication and wiring. That's what I have. I just mention the stud mounted switches for those who don't want to go to that much trouble.

I suppose you could use two of those switches for cases, like you mention, where there are too many wires to elegantly have them all go through a single switch. Perhaps one stud mounted switch and one post mounted one.

djbar · 10-05-2019, 08:41 AM

Battery disconnect switch is on my to-do list. Will prob use BlueSea switch on batt box. Wondering about pro’s and con’s of 2-way vs 4-way switch. Thoughts?

PKI · 10-05-2019, 11:06 AM

Just remember to energize the systems before towing. Since you usually need the jack, this is a bit self evident, unless you switch off the loads while hitched. The point is that however you disconnect your batteries, the brake circuit needs power to activate the brakes in a hitch disconnect event.

A battery disconnect switch may be the best mod that you can make to your rig. The cheep disconnect switch is the disconnect the cables from the battery. Only cost is your labor. But an ASer needs to glamp the install with a switch. It's also much easier to just throw that switch.

Good luck with your project. Hope to see you down the road. Pat