Friday, July 30, 2021
Friday, July 30, 2021

RV battery disconnect switches: how, when and why

By Steve Savage, Mobility RV Service

Got a battery disconnect switch on your RV and wonder how to use it? Whether your switch is the “manually thrown” style or an “automatic push-button,” they all do the same job: They break the connection between the battery and the 12-volt fuses providing power to lights, appliances and so on.

You should know that basically all appliances depend on 12-volt battery power to activate module boards, even if the appliance like an air conditioner runs on 120-volt power.

It all boils down to this: When the disconnect is thrown, the only way things depending on 12 volts will work is when the RV is plugged into the shoreline. Once plugged in, the power converter or inverter/charger provides power even when the disconnect is thrown.

So suppose you are plugged into shore power and your refrigerator is set on the “auto” function, which means it would normally switch over to propane if the RV was unplugged from shore power. If the disconnect is turned off and if shore power should go out or you unplug your rig from shore power, the refrigerator will not switch to propane. This is because the module board has no 12-volt power. The lights won’t work, either, nor will the furnace or water heater, until you plug the shore line back in or you turn the disconnect back on.

So what is a disconnect for? The disconnect should be turned off when you store your camper so your batteries discharge more slowly. Mind you, they’ll still discharge spontaneously over the course of several weeks, but with the switch off it’ll take longer. Using your disconnect switch in this way ensures longer life for your batteries. So if a little is good, how about turning it off every time you leave your RV? Doing that when you are plugged into shore power also disconnects your batteries from the charging circuit of your power, meaning that even if the rig is plugged into shore power, your batteries will not charge.

My advice? Keep it simple. Turn the disconnect off when you’ll be away from your rig for a significant period of time, as in a week or more — otherwise, leave it on. There is enough to remember when camping without having to remember the position of the disconnect switch on your batteries!

What should you do if you are going to store your RV and do not have a disconnect switch? You can simply remove the negative lead from your battery — but a better solution would be to install a manual disconnection switch. They are cheap and take only a few minutes to install.

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Edward Garcia
2 days ago

When charging rv battery to home 110 outlet. should the battery be connected, or disconnected and the inverter should the breaker at panel be turned to on position?

Chris Duncan
7 months ago

I’m confused by this post. If the disconnect is off, doesn’t that 12V is on. If disconnect is on wouldn’t that mean 12V not on?

Richard Butler
1 year ago

Battery s are charged, no power,will not start, no power in coach, class A bounder, Fleetwood 1998 anybody have an idea? Disconnect switches Don’t work

Shawn
1 month ago
Reply to  Richard Butler

Bad ground somewhere or loose battery connection to coach from battery or altenator

JIM ODELL
1 year ago

So, as the batteries no longer charge when the switch is off, why would it not be advisable to leave it on when stored & connected to shorepower?

Jan Garrett
10 months ago
Reply to  JIM ODELL

that’s what I’m thinking

Mike Sullivan
7 months ago
Reply to  JIM ODELL

Because converters don’t have overcharge protection and you can slowly boil away the water in your batteries below the top line if you don’t check them every month. Been there, done that. I now just take them out and put them in the garage on a BatteryMinder that not only has overcharge protection but also desulfates the batteries. Just sold a bumper pull that was 8 years old and still had the original battery.

Patricia
1 year ago

I have solar panels on my RV when do I turn my battery disconnect off? Should I leave it on all the time for the solar to connect?

Christopher Rood
1 year ago
Reply to  Patricia

Patricia, sorry, no answer from me. just wanted to say I have the same question and I haven’t found a clear answer from my reading. any expert want to help Patricia and me out? Chris

kristi link
1 year ago

Me too. An answer would be great!

Mike Sokol
1 year ago
Reply to  kristi link

If you have a solar battery controller with a battery tender function, you can leave your battery switch ON so it will receive a charge from your solar panels. That should easily be enough make-up current to offset any parasitic loads from your smoke detector and LP alarm, etc…

S Taylor
15 days ago
Reply to  Mike Sokol

I have a Alpha Wolf RV. I have taken readings and monitor my batteries regularly, and I have found when the battery disconnect is off, I still get more than 13-14 volts of incoming charge to the batteries from the 50W solar cells. So yes, the disconnect cuts off the shore power charge, but does not cut off the solar charge from the controller.

Shawn
1 month ago
Reply to  kristi link

If it’s an external panel like a Coleman ect, you can turn off your disconnect switch and hook up the panel direct to the battery post as most have an overcharge protection built into them and only charge at a max of 7.5 amps, if it’s an onboard panel plug in it will be designed to only charge at 2 amp while the switch is off so it doesn’t backfeed to the converter so in short your solar panel is designed to keep your battery charged when your units disconnect is off, I leave mine hooked up whether it’s plugged to shore power or not in case power goes out and I’m not around and take the batteries out and connect them to a maintainer for the winter and have had no problems, hope this helps

Nikki Harnish
1 year ago

How does disconnecting the battery affect the CO detector and smoke detector?

Shawn
1 month ago
Reply to  Nikki Harnish

Unless you’re plugged into shore power No battery=no power=no smoke detector or CO monitor

Shannon Yoder
2 years ago

We just bought a Keystone Premier Bullet and can’t find the battery disconnect switch. Our last one had it in the storage are. Does anyone know where it?
Thanks

Cypress clark
2 years ago

I have a push pull switch to disconnect battery. But not sure which is which…when pulled Out is it disconnected ( pushed in means it is connected)? Seems silly question, but I can’t find info on this little detail.

Terry Hennessy
1 year ago
Reply to  Cypress clark

Since no one answered? While unplugged from shoreline, turn on a light, and then make yourself a LABEL and cover w/ Magic Tape or clear shipping tape.

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