RV battery disconnect switches: how, when and why

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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