When you are boondocking off the grid in your motorhome or camper, you need to rely heavily on your RV’s house batteries.

Even if you have the supplies and storage tanks to stay off the grid for days at a time, you will still probably need to come up with a way to safely and efficiently recharge your RV’s batteries without returning to the civilized world.

Though not every camper battery charging method is safe for your batteries and your RV’s components.

The following are some of the most popular ways to charge a 12 Volt deep cycle RV battery. Each has its benefits and drawbacks.

It is also important to note that we are talking about the “House” battery bank inside the RV or camper that runs the interior lights and appliances. These batteries are not directly connected to the electrical system in the vehicle’s engine bay.

Testing The Charge In Your RV’s House Batteries

Whichever of the following battery charging methods you use, the first step is always to check the power level inside the battery.

This calls for using a voltmeter or a multimeter connected to the battery posts. A 12 Volt RV house battery that is fully charged will give you a reading of 12 to 12.6 Volts.

If your battery is reading less than this, then it is likely in need of a charge.

It’s also worth noting that a battery that is allowed to go below half its maximum charge for a prolonged period of time can suffer damage to the internal components.

This can limit how much charge it will be able to hold in the future. Some damaged 12 Volt batteries have been so badly compromised that they can no longer hold a maximum 12 Volt charge.

How Long Does It Take To Charge An RV House Battery?

A 12 Volt deep cycle RV house battery that has been depleted to around 50% of maximum charge, that is hooked to a traditional battery charger will take roughly four to seven hours.

This can also depend on whether you are trying to rapid charge it at the high amperage setting or trickle charge it on the low amperage setting.

5 Methods For Recharging RV House Batteries Correctly

Method1: Charge RV Batteries With The Battery Tender

A standard battery charger and a smart charger are very similar in that you plug both of them into a 110 Volt AC outlet. It then converts that electricity to DC which the 12 Volt battery runs on.

This is a sophisticated battery charger with onboard monitors and programming battery very versatile to charge almost any type of battery ranging from AGM, lead acid, gel, lithium, and sealed. Also known as a “Battery Tender” it actively reads the ambient charge in the 12 Volt battery and alters the amount of charge it delivers.

This is the ideal way to charge an RV house battery as it reduces the heat and helps prevent the potential damage that can be caused by overcharging.

Of course, you do need to have it plugged into some type of 110 Volt AC outlet, which might not be feasible if you are boondocking off the grid.

If there is no shore power available where you are, you would need to improvise a different way to power it.

Some of the best smart chargers have multiple settings to address different conditions and situations.

The rapid charge setting quickly boosts the battery but isn’t ideal for charging it to maximum capacity.

With some batteries frequently using the rapid charge setting can start to compromise the internal components or affect the internal electrolyte levels.

Some of the smart chargers also have settings that let you adjust how it charges in cold weather or settings that change how it delivers the charge if you happen to have a gel-based RV house battery instead of a typical lead-acid 12 Volt battery.

Trickle charge or standard charging mode slowly recharges the 12 Volt deep cycle RV battery to the maximum, though it certainly takes longer.

This setting is ideal and it’s the mode you want to use when charging the battery overnight or perhaps while you are out for a long hike.

Charge The RV Battery With A Battery Or Smart Charger Plugged Into Shore Power

Method 2: Charge The RV Battery With A Battery Or Smart Charger Plugged Into Shore Power

If you just purchased a battery charger or a smart charger, give yourself the time to read through the owner’s manual to familiarize yourself with that particular model.

That way you will know what each button, dial, and setting are used for. Once you have a confident understanding you can use the following steps to recharge your RV house battery with a traditional battery charger or smart charger.

Step 1: Connect The Battery Charger To The RV House Battery

Start by attaching the red “Positive” clamp to the red positive post on the battery. They typically have a “+” sign stamped or printed on them.

Then attach the black negative clamp to the negative post on the battery. It typically has a “-“  sign stamped or printed on it.

Step 2: Plug-In The Battery Charger

You will need to plug it into a standard 110 Volt AC outlet like you might find on a campsite power post or there might be something available through a shore power connection.

In a pinch, you might also be able to use an AC outlet on a generator if your generator happens to have one.

Step 3: Set Up The Smart Charger

At this point, you will need to set the volt and amps on the charger. Ideally, you want to set it up to deliver a trickle charge to the RV house battery.

This means setting it up at a lower amperage than if rapid charge. If you do need to rapidly charge the battery, then you will set it to the higher amperage setting.

Step 4: Activate The Charger

Most smart chargers have a setting that activates the mode you just set it up for.

Though before turning it on, take a moment to visually inspect all the wires and cables to make sure they are secure and out of the way. Then let the charger run and it will charge the battery as needed.

Step 5: Disconnecting The Charger

Once the 12 Volt RV house battery is fully charged you should turn off the charger before unplugging it from the AC outlet.

Then you will disconnect the cables in the opposite order in which you attached them. Start by disconnecting the black negative clamp first, followed by the red positive clamp.

The Differences In Disconnecting A Traditional Battery Charger And A Smart Charger

If you are using a traditional battery charger you will need to be mindful not to overcharge the RV house batteries.

This means keeping an eye on the charger or testing the 12 Volt battery with a multimeter or voltmeter.

If you are using a smart charger, the battery tender programming inside it will monitor the charge inside the battery and alter how it delivers electricity to the battery to help prevent overcharging and heat build-up.

This lets you leave it on the charger overnight or while you are out on a long hike without worrying about the battery.

Though you will still need to disconnect the smart charger in a reasonable amount of time.

Use A Generator To Power A 12 Volt Battery Charger

Method 3: Use A Generator To Power A 12 Volt Battery Charger

If you have a generator built into your RV or you have a secondary aftermarket generator it is possible to recharge your house batteries, by connecting it to a traditional battery charger or a smart charger.  

If you are using a traditional battery charger without any sort of battery tending feature, then you need to be present throughout the entire charging process.

You can do something like step away to use the restroom or make a sandwich, but you shouldn’t take a hike or leave it set up charging overnight.

When you are ready, you can use the following steps to charge a 12 Volt camper battery directly from a generator.

  • Step 1: Start by inspecting the 12 Volt RV house battery to make sure there isn’t a physical defect affecting its performance. If the electrolyte levels are low, you should first try to refill it with distilled water to the full mark inside each battery cell. Any corrosion or discoloration on the power posts needs to be cleaned with baking soda paste and an old toothbrush to ensure a good connection.
  • Step 2: Fuel up the generator and check the oil.
  • Step 3: Start the generator and let it run for 3 to 5 minutes to warm up.
  • Step 4: Attach the battery to the battery charger. Start by attaching the red positive charger clip to the positive terminal on the battery. Then attach the black negative clip to the negative terminal on the battery.
  • Step 5: Plug the battery charger into the generator’s 120 Volt AC outlet. Confirm that the battery charger is operating according to the manufacturer’s specifications. You can set it to the lower amperage setting for a slow trickle charge, or set it to the higher amperage setting for a rapid charge.  
Use A Solar Panel Or Wind Generator To Recharge An RV House Battery

Method 4: Use A Solar Panel Or Wind Generator To Recharge An RV House Battery

Green energy technology has continued to advance to the point where high-quality solar panels and small wind generators sold at the retail level are capable of trickle charging an RV house battery.

Though this is more for maintaining the charge in the RV house battery than it is to recharge a battery that has been depleted below 50% of the maximum charge.

A solar panel or a wind generator that has a rating of at least 100 Watts is capable of producing around 6 amps at peak operation.

This translates to around 30 amp-hours daily. In ballpark terms, you would need two 100 watt solar panels or a wind generator with a 200 Watt maximum rating.

Then, of course, you also need mother nature to provide you with a sufficiently sunny or windy day.

In a scenario like this, you can expect your solar panel or wind generator to be able to recharge a 12 Volt RV house battery from 50% to 100% in roughly 5 to 8 hours. Depending on the conditions.

Method 5: Use Your Vehicle’s Alternator To Charge An RV House Battery

Charging RV house battery from a vehicle is the last viable and least safe option to consider and should only be done if you are in a pinch and have no better means to recharge your RV battery.

You will need to have the engine running on your motorhome, pickup truck, or another type of tow vehicle.

You should also note that this can tax the vehicle’s alternator, and doing it repeatedly could shorten the alternator’s lifespan.

Ideally, you want to use a 4-pin connection like the one that power’s a trailer running lights.

This will trickle charge the battery slowly, which will also use a fair amount of fuel. If you don’t have a 4-pin connection, you can use jumper cables, and leave the two batteries connected while the truck runs.

This should recharge a battery from 50% to around 100% in one to two hours.

Just stay close, check the battery level with a multimeter or voltmeter, and disconnect the RV house battery once it reaches around 90 to 95% of maximum charge.

Can I Charge A 12 Volt Battery From Multiple Sources At The Same Time?

Technically, you can charge your 12 Volt RV house batteries from multiple sources at the same time without hurting your batteries.

Though you need to be mindful to not overcharge your batteries. If you have it connected to solar panels and a wind generator at the same time or a traditional battery charger, you need to disconnect the battery as soon as it hits maximum charge to prevent overcharging.

Is It Bad To Overcharge A Battery?

Leaving a 12 Volt battery like an RV house battery on a standard charger or connected to a DC power source for a few minutes or even an hour won’t severely damage a battery that is in good working order.

Though overcharging a battery for too long can damage the electrolytes and other components inside.

This can drastically reduce the battery’s lifespan and lead to over potentially severe consequences.

A severely overcharged battery can potentially boil over to the point where it causes the seals to fail on the battery case.

When this happens the battery can spill a dangerous amount of battery acid on the battery pan and surrounding components.

Some overcharged batteries can even crack the case leading to catastrophic acid damage to the surrounding materials.

What Happens If I Drain An RV Battery Below 50%?

Lead-Acid batteries can suffer damage to the interior components if they are frequently drained below 50% or left to sit uncharged for long periods of time with less than 50% charge.

It’s best to monitor battery levels with a voltmeter or multimeter, even if they are stored away for the winter.

If the levels start to drop below 75% putting it on a smart charger will help maintain good working order when you are ready to use it again.

Can I Check The Electrolyte Levels In An RV Battery?

Some lead-acid batteries have removable seals on the top of the cells. This lets you open them up to inspect the electrolyte levels.

If you happen to notice that one of your 12 Volt RV house batteries is low on electrolytes you can carefully top it up by adding a small amount of distilled water.

Just make sure that it is distilled and uncontaminated. Springwater, filtered water, and tap water all contain trace minerals that can react negatively with the remaining acid in the battery cells.

It’s also worth noting that not all RV batteries can be opened this way. Some 12 Volt batteries are sealed for safety reasons.

Also, newer gel batteries, cannot be opened and checked or topped up as they use different chemical components.


There are a few different ways to charge your RV’s 12 Volt house batteries. The best option is to use a smart charger or battery tender that is plugged into an AC outlet.

If you don’t have AC power available, you can plug a battery charger into an AC port on a generator. Most modern generators have at least one 120 Volt AC outlet.

Just bear in mind that if you are going to use a traditional charger without any battery tending features, you will need to stay close at hand.

Then disconnect the battery as soon as it reaches full charge to prevent potentially dangerous and damaging overcharging.

Connecting your battery to a solar panel or a wind generator that is rated to produce at least 100 watts is also a great way to help maintain your RV’s house batteries without having to resort to a traditional charger.

This is great for times when you might be out fishing or on a long hike and the battery isn’t being actively used by appliances and lights.