Should I Disconnect My RV Battery When Plugged In?

Your RV battery, or the house battery, supplies your electronics with the juice every time you are not plugged in or running a generator. It could run through a DC to AC inverter or directly when powering DC loads.

You could run your home off deep cycle lead-acid batteries or the more modern and efficient Lithium Iron Phosphate chemistry. Regardless of what you go for, RV batteries are costly. Anything to prolong their lifespan will ultimately save you a pretty penny.

Does disconnecting the batteries when plugged in and not using them help? Here is an in-depth look at how your RV house batteries work and whether you should bother with disconnecting them when parked.

Quick answer: No. You don’t have to if you use a smart battery charger that won’t overcharge them.

How Does the RV Power System Work?

A properly built RV can receive power from batteries, generators, or shore power. Standard installations prioritize shore power before defaulting to the generator and, finally, your batteries.

Unless you have a built-in generator that connects to the electrical panel at a different point, chances are you plug in your generator through the shore power plug. In this case, your RV treats generator power and RV power as the same thing.

What Happens When You Plug-In?

Here is a series of events that happen every time you plug in your RV:

  • A changeover switch in your main circuit breaker board (or inverter charger) turns off the onboard inverter and feeds all your AC power outlets direct from the plugged inshore power
  • A DC converter turns some of the plugged-in AC power to DC to run any DC loads
  • A battery charger draws some power from AC power to recharge or keep your RV battery charged

At this point, the changeover system has effectively disconnected your battery from the loads, and the battery charger juices it up or keeps sending a maintenance charge.

If your RV has the proper battery charger or uses an all-in-one inverter charger, you can remain camped for years, and your batteries will be happy with it.

ProTip: You shouldn’t disconnect your RV batteries even if you plan to keep your RV plugged in for a very long time. 

  • If they are Lead-Acid, they will get the constant float charge they need to counter self-discharge
  • If they are Lithium chemistry, the charger will top them up and stop charging until when you pull out some charge

Your batteries will be ready to go the day you decide to unplug or if there is a power blackout.

What Happens if You Turn on a Generator?

If you have a generator directly wired into your main electric board, the same changeover happens every time you turn on the generator.

It will run your RV electronics while recharging your batteries. Some RVs have standby generators that kick in when the battery bank charge drops below a threshold and run long enough to recharge them before shutting down again.

Either way, you still don’t have to disconnect your batteries.

Disclaimer: This Will Only Work if You Have a Smart Battery Charger

Older RVs and rudimentary charging systems use a traditional DC-DC or AC-DC converter to send current at a fixed voltage to the battery bank. While this will charge the battery bank, it can’t tell when the batteries are full and won’t shut off accordingly.

Modern RVs or all-in-one inverter chargers have smart MPPT or PWM charge controllers that shut off after fully charging a battery. You don’t have to worry about over voltage, over current, or overcharge situations with these.

When to Disconnect RV Batteries

With the right charger, you never have to disconnect your batteries from the RV unless you want all power off. 

You should find a way to provide trickle power to the batteries (especially if they are Lead-Acid) to keep them topped up. This power could be from the shore power plug or the solar panels on the roof.

Some of the opportune times when you could disconnect your RV batteries are:

  • When you want to maintain your RV power system
  • When you want to upgrade some components in the systems
  • When you want to replace the batteries
  • The RV is going to storage for very long, and you want to minimize parasitic loads and use a more efficient trickle charger connected straight to the battery.
  • When there’s a fault in your electrical circuit, like a short circuit, and you want to shut off the power quickly

The Disadvantages of Disconnecting Your RV Batteries

The main disadvantage of disconnecting your RV batteries is that you will have no power if something interrupts your shore power or your generators turns off. 

All the electronics in the RV will go off until you switch and plug the batteries back on. This can be quite an inconvenience. 

Best Way to Disconnect Your RV Batteries

Don’t think of using a wrench to undo the lugs connecting terminals to your battery. While this will do the trick, it is too much work and potentially dangerous. A simpler alternative is using an RV battery disconnect switch.

Most well-built RVs and motorhomes come with the switch already installed. If it isn’t a switch, it will be the main circuit breaker to the battery. All you have to do is flip it off, and the battery will be disconnected.

Since the battery isolator or disconnect switch controls the main positive (or both positive and negative) leads from your battery, it should have the right wire gauge and capacity to handle many amperes.

Most manufacturers and aftermarket modifications put it as close to the battery bank as possible. It will be a few feet from the battery or next to the battery bank. 

You could go for a relay system if you want it in the RV or next to your favorite control panel. The relay control wires can run further since they don’t carry so much current, while the load section will make a shorter run and remain next to the battery.

You could also get a battery to protect the system with a relay that you can shut off from a remote control panel or via a Bluetooth app on your smartphone.

Oscar

In his spare time, Oscar loves tinkering with electronics. Solar panels, wiring, old TVs and sometimes DIY powerwalls. When he is not busy trying not to electrocute himself, you can find him in the garden tending to his vegetables and chickens.

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