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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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Chief
11 days ago

I have a class C motor home last night we narrowly missed a mishap, I awoke about mid night there was a noxious order in our Rv, we had a battery failure the charger kept trying to charge the battery which resulted in the battery overheating and leaking out fluid,battery disconnect was in the on position we were connected to shore power, should the battery disconnect be in the on or off position when hooked to shore power.

Mimi
1 month ago

Trailer sitting all through pandemic at Park with shore power but now nothing seems to work Battery disconnect is in ON position, but nothing is working except lamps plugged in. 12v fixtures verrrrry dim. Do I need new battery?

jeff
23 days ago
Reply to  Mimi

had same issue.found out that one of breakers was toggled.reset breaker and bodda bing.

Edward Garcia
4 months 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?

jeff
23 days ago
Reply to  Edward Garcia

i charge battery seperate at home. leaving 110v plugged in doesnt really charge battery unless using things that requir 12v usage. thats why i disconnect battery for period of time and charge or trickle charge battery seperate,while not plugged into 110v.

Chris Duncan
11 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?

jef
23 days ago
Reply to  Chris Duncan

disconnect means 12v off.on my winnebago the propane gas detector is always using the 12v supply(found out hardway ,after replacing battery).12v
the battery is for lights all around camper,slides,and water pump.12v does not work on frig or microwave unless frig has a converter for you to switch over. that way if your boondocking you can use all the 12v battery has to offer and switch propane over for frig .cant use microwave without 110,but everything else ok

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
5 months 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
1 year ago
Reply to  JIM ODELL

that’s what I’m thinking

Mike Sullivan
11 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
4 months 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
5 months 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

jeff
23 days ago
Reply to  Shawn

doesnt solar panels charge batteries to use all on camper that uses 12v supply. thats what it suppose to do.because everything on camper uses 12v(lights,slides,some friges,water pump if fresh water in tanks). so if no solar panels and no ac the battery will drain over time.thus a solar panel will charge batteries and you can go on for a while without ac.

Nikki Harnish
2 years ago

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

Shawn
5 months 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

Patti
2 months ago
Reply to  Shannon Yoder

Most articles and YouTube videos I’ve seen showed them on or near the battery. Mine is near the water hook-ups.

2017 Forest River/Prime Time Crusader Lite 28RL

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
2 years 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.