How to Charge RV Battery with Generator – The Correct Way!

When referring to RV batteries, most people mean the 12 volt House Batteries. These are the large, more complex batteries that often come in banks more than single units. They are what power things like the TV and appliances when not hooked up to shore power.

The most common type of house battery are 12 volt Flooded Lead Acid batteries, also known as a wet deep cycle battery. As they charge and discharge, they vent gasses out through the caps. They need regular maintenance, included replacing lost water and keeping them above a 50% charge for optimal life.

Despite this, they remain popular due to their balance between price and performance.

To charge your 12 volt RV or camper batteries with your portable generator is fairly simple, and you have a few options. The first involves using a battery charger between your batteries and the generator. The other involves plugging the RV itself into the generator.

Safety First

Before interacting with your batteries in any way, make sure you have the proper equipment:

  • Insulated Tools
  • Insulated Gloves
  • Safety Goggles

Instructions – How to Charge RV Battery with Generator

There are two different ways to do this, with the first being the simpler of the two – but often the slower method as well. The second method is a bit more involved, but proves a little faster.

Before we charge the RV though, let’s do a little maintenance on the RV battery.

RV Battery Maintenance

Even if your battery is a maintenance free model, there are a few key things you should always keep in mind. Deep Cycle batteries can safely drop below 20% on occasion, but it’s unhealthy for them. Ideally, you should always make sure that if the battery drops below 50% – you charge the battery.

If your battery says “Maintenance Free” anywhere on it, you can safely ignore the last line.

  • Turn off your RV and put the emergency brake on.
  • Locate the 12 volt (or 6 volt) batteries on your RV – this can differ from model to model. Check your owner’s manual if you’re not sure.
  • Perform a visual inspection of the battery, checking for cracks, bulging or corrosion. Corrosion can shorten the life of your battery, and should be cleaned off.
  • If there is any cracking or bulging, remove the battery from service immediately. Do not attempt to charge this battery.
  • Remove the cables from the battery terminals. As always, be careful not to allow any metal to bridge the terminals.
  • Using a mixture of baking soda and water, scrub around the terminals to remove any dirt. With a small wire brush, remove any leftover corrosion. Allow for every part of the battery to dry before you start to charge.
  • Unscrew the cap from the battery and check the liquid level. If it’s below the full line, add distilled water until it meets the line. If your battery says “Maintenance Free” anywhere on it, skip this step.

First method – Plugging The RV In

When charging an RV or camper battery this way, you should be aware – it can be much slower. This method requires powering the entire electrical system of your RV or camper. You can run your appliances this way, but it will slow down how quick you can charge rv.

If your recreational vehicle was built before the mid 2000s, the battery charger built into its system may only provide a slow trickle charge.

Important Note: Make sure that the generator is compatible with your RV’s power systems. RVs with 15A and 30A plugs should work with any generator that outputs 120V power. If your RV has a 50A plug, you will need a more powerful generator.

Step 1

Unplug everything from the power system in the RV to maximize charging capacity, and make sure the AC and fans are off if possible. This will allow the generator to expend almost all of its energy towards charge RV.

You can run appliances such as the fridge if need be, but every appliance plugged in will slow down the charge.

Step 2

Inspect the shore power plug on your RV. If it’s a standard 15A plug, you’re good to go – these are shaped like your every day house plug.

If the plug is 30A, you may need an adapter. Some generators have these outlets, so it depends on the model you have.

Step 3

Fill the gasoline or other fuel tank on your generator and power it on. Let it run for approximately 3-5 minutes before plugging in the RV.

And that’s it! Your generator will continue charging the batteries until they’re fully charged. There isn’t really one catch all amount of time to be given for this – it’s highly dependent on the model of both your RV and generator. This method does tend to take longer, and consumes more fuel than the second method.

Second Method – Portable Battery Charger

This method is a little more involved, but charges faster.

We’re using the portable generator to plug in a three-stage portable charger. These chargers automatically adjust and reduce their power to prevent overcharging the battery. By opting to plug the battery charger into the generator, we speed up the charging process.

By speeding up the charging process – we are saving money on fuel for the generator and reducing pollution.

Step 1

If your RV has a Battery Disconnect Switch, flip that to disconnect them from the electrical system. We do this to make sure that when we turn on the generator, we’re not sending electricity to the appliances or anything plugged in.

If you’re unsure if your RV has a Battery Disconnect Switch, check your owner’s manual. If it doesn’t, make sure the batteries are disconnected from the system before attaching the battery charger.

Step 2

Locate the house batteries on your RV. This is different on every vehicle, the owner’s manual should be able to help. Perform a visual inspection, looking for corrosion or signs of damage.

Step 3

Fill the gasoline or other fuel tank on your generator and power it on. Let it run for approximately 3-5 minutes.

Step 4

Plug your battery charger to the portable generator. Check the status lights to ensure it is working properly.

Step 5

If charging a single RV battery at a time, remove both cables from each battery. Start with the negative cable, marked by a minus sign (-). Then remove the positive cable, marked by a positive sign (+). Be very sure that any metal touching the terminals doesn’t touch any other metal.

Attach the Black Negative (-) cable from the battery charger to the Negative (-) terminal of the battery. Then attach the Red Positive (+) cable from the battery charger to the Positive (+) terminal of the battery. When the battery is fully charged, move to the next one.

If charging a battery bank to full charge all at once, consult your owners manual. There are different set ups, and the owner’s manual should give precise instructions for your situation.

Other ways to charge your RV Battery

When seeking charging solutions for your RV battery, a generator isn’t your only option. While a portable generator does offer a certain degree of freedom, it also brings smoke and noise to the table. Solar panels are one example of an environmentally healthy solution, often used in conjunction with a generator.

Solar Power

Solar Panels offer a green solution, though usually charge slower than using a portable generator. Additionally, cloud cover could inhibit the power flow from the solar panels when charging RV batteries.

Many modern RVs use a combination of generator and solar panels to charge, depending on the situation.

Shore Power

This is one of the better ways to bring your RV battery to full charge. Shore power is a boating term, and refers to any power source that isn’t portable or connected to the RV’s power system. It is superior to using a portable generator most of the time.

Before you start charging an RV battery off of shore power, make sure that it’s a power source you trust. If you’re not 100% sure, use a surge protector to protect your RV. Check out our review of the best RV surge protectors.


Using your portable generator to charge your 12 volt RV battery system can be a tricky procedure.

Just remember – any time you’re working with a battery, follow these simple rules to protect yourself:

  • NEVER allow metal or any cable to bridge the gaps between the two terminals on a battery. This can cause severe damage to the battery and to your person.
  • NEVER allow the positive cables leading from your battery to touch metal. If they are still connected to the battery, it will begin discharging electricity into the metal. This can cause injury, death, or severe damage.
  • ALWAYS inspect your RV battery before performing any maintenance or charging operation. Look out for bulges, cracks, or any other signs of damage. If you see any of these, immediately remove the battery from service and replace it. Clean corrosion before putting battery back into service.
  • ALWAYS charge your battery in a well-ventilated area when using a battery charger. During the charge cycle, your battery can produce toxic gas during their charging cycle, that can quickly build up to toxic levels.

By following this guide, you can ensure that you charge RV correctly, and keep your system well maintained. Remember, always check the owner’s manual or manufacturer’s website before performing maintenance on any vehicle or device. There are many different models of RV, generator, battery charger, and battery – play it safe. If you liked this guide, then check out the best RV battery reviews, how to change an RV battery while driving, and the best RV generator review on this page.

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