How to Charge RV Battery with Generator

Keeping your RV batteries topped up is something that any RVer quickly realizes is a necessity. Even those who didn’t understand how quickly battery power gets drained, they learn fast!

There are different approaches to ensuring batteries remain always topped up. These include while towing your RV, at an RV campground, or using a generator.

For larger motorhomes and an RV towable like a fifth wheel, a modern generator may come included. It’s also possible that the existing generator is at the end of its useful life and/or doesn’t offer enough capacity or outputs to be very useful.

Smaller travel trailers or campers likely didn’t come with one. Then you’ll need a portable generator to take on your travels and plugin as needed.

How to Charge RV Battery with Generator

RV generators are different from other kinds.

They’re specifically designed for people who travel. Typically, they have multiple outputs, may support multi-fuel options, and allow for powering appliances and charging your 12-volt house battery bank concurrently.

It’s always a good idea to read up on your generator model first. This way, you’ll know what to expect and can turn it off quickly should you need to.

Always Prepare Your Battery Bank First

Tip: Whenever you’re working with batteries, wear safety eyewear and gloves for this purpose. It avoids any escaped fluids or other matter touching your skin or eyes.

Most RV house batteries are the deep cycle type. If they’re not lithium and have fluctuating levels, then it’ll be necessary to verify the fluid for each battery.

Some battery types may use distilled water that needs to rise above the plates inside the battery itself. This forms part of normal battery maintenance requirements, which the manufacturer will be able to confirm.

The exterior of the batteries inside a battery bank can pick up dust, debris, and possible corrosion too. Look at them and use a brush to carefully remove anything unwanted from their surface.

It’s cleaner, safer, and allows for more efficient charging too.

Using a Built-in RV Generator

If you’re lucky enough to have a built-in model, they will be set up to charge the house batteries. It’ll usually have an RV converter that transforms the standard 120 volts across to the 12-volt DC power that house batteries require. In so doing, a generator to charge 12v battery installations works fine.

It should be only a matter of looking at the RV instruction manual if you don’t already know how to hook everything up. Using as few RV appliances while charging up the battery bank shortens the recharging time.

Run the generator when you’re away from other RVers and it’s not an inconvenient time of day. RV parks will have restrictions on generator usage including limited times when it’s permitted.

Even if boondocking, sound carries for miles unobstructed. Distant neighbors won’t take kindly to the interruption to their peace. Bare this in mind to avoid having someone highly agitated banging angrily on your RV’s door!

Read Also: RV Solar for Beginners

Portable Generator to Charge Battery Bank?

Choosing a dependable, portable generator is essential if you don’t have an onboard one or it’s unreliable. It must have sufficient capacity both with fuel and energy output as a generator to charge battery banks. Then your RV batteries can be topped up regularly and well-maintained.

For example, charging RV batteries with a Honda generator is possible using this Honda 3,000-watt, 120-volt model:

Honda Power Equipment 3,000W 120V Portable Home Gas Power Generator (Model EU3000IS1AN)

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5 Stages for How to Charge RV Battery with Portable Generator

Stage #1 – Confirm the amount of available fuel/oil in the generator. Review the air filters too.

Don’t run the generator with insufficient fuel or a clogged air filter. It could sputter and send a spike or surge to your battery bank.

Stage #2 – Position the portable RV generator outside

It needs to be a short distance from the RV. Place it on flat, level ground, and preferably on a stand to keep it dry. This is required to vent any fumes generated from the gasoline, diesel, or other fuel source used to power the RV generator.

Stage #3 – Follow the startup procedure for the portable generator

Each portable generator is different. Our example one above requires a set procedure including turning off the throttle, enabling the fuel, and closing the choke before turning it on. Read the instructions for your RV generator to do it the correct way.

Stage #4 – Give the generator time to stabilize itself

Smooth, regular power is what’s required of your portable generator. This allows you to confirm that it’s functioning well before hooking it up to your precious battery bank.

Stage #5 – Hook the generator up to the RV

The power cord from the RV may plug directly into the portable generator. You may need an WEN Twist-Lock RV adapter. In case of incompatibility, try the 30-amp twist adapter below:

WEN NEMA Twist-Lock Power Plug to TT-30R Ready Outlet, 120V 30-Amp 3600-Watt Generator to RV Adapter – Black (Model GNA030 L5-30P)

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Read Also: How to Charge RV Battery from Vehicle

Read Also: How to Watch TV with a Generator


What size generator to charge RV battery?

When you’re charging a deep cycle battery with a generator, it’s good to know what to expect.

If using the built-in RV generator but are running 120-volt appliances at the same time, then it won’t recharge the house batteries as quickly. The spec from the RV model’s manual will only be able to supply rough estimates from when the RV is not in use.

For portable generators, you may also have other appliances plugged into them and powered at the same time. This reduces how quickly your house batteries will be topped up.

A generator in the 3,000 watts to 4,000 watts capacity range is what’s required to completely recharge RV batteries using the 12-volt system. Practically speaking, the more watts, the better!

Furthermore, an RV inverter generator is a better option than a regular generator. This is because it will regulate the power output to help avoid spikes during recharging cycles.

How fast will a generator charge a battery?

The total time to recharge RV batteries depends on how many batteries there are, how drained they’ve become, the output of your RV generator, and how many amps can be received too.

Using a multi-stage, 12 volt generator battery charger with a higher capacity will help to harness the generator’s power and safely direct it to the house batteries. It will also ensure that no batteries get overcharged and damaged.

For instance, the Renogy battery charger offers reliable DC to DC charging and comes in 30-, 40- and 60-amp capacities:

Read Also: Quickest Way to Charge RV Batteries

RV battery not charging from generator

If your built-in RV generator isn’t giving your house batteries a charge up, you’ll need to look more carefully.

Follow these steps if you’re having generator charging issues:

  1. Verify that the connections to the battery haven’t worked loose during a long journey.
  2. The converter circuit breaker could have tripped and now be off. Alternatively, one of the fuses might need to be replaced.
  3. The generator may have one or 2 breakers. Look for both and ensure they haven’t tripped.
  4. Eyeball at the batteries themselves too. See if they are short on electrolytes and need more distilled water, cleaner battery terminals, or other remedial actions.

If you feel uncomfortable working on these systems, hire an RV workshop to troubleshoot what’s wrong and fix it for you. Have them explain it as well, so you can learn from the experience.

Is using a generator the fastest method to recharge RV batteries?

There are various quick approaches to complete an RV battery charge up. Using a generator is perhaps the noisiest and so it’s always good to know other approaches.

Our article on the fastest RV battery charging methods is worth a look too.

Closing Thoughts

Using a built-in generator or a portable generator to recharge your RV batteries can solve many problems. It’ll need to be performed at an appropriate time and place to avoid upsetting nearby RVers.

Also, ensure your generator has sufficient wattage to charge the batteries in a timely fashion. They’ll likely need several hours to fully recharge and if the generator’s output is on the low side, it’ll take much longer.

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