Class C Motorhome

How Do Camper Batteries Get Charged?

In RV living by Christopher Schopf

When I was looking to get into RVing, I had visions of exploring the country and doing work on the road.  I knew that while on the road I’d need power and learned that the power would often have to come from my RV’s battery.

It seemed obvious to me that the battery would eventually die and I’d have to charge it but I wondered how do batteries get charged.

How Do Camper Batteries Get Charged?
A camper’s battery usually charges through the use of a converter which takes AC power and converts this power to DC power.  Alternatively, a camper’s battery could be charged directly through the tow vehicle’s alternator, solar power, or even wind power.

Charging a Camper Battery Through The Converter

There are a few ways in which a battery can be charged using the converter.  The camper could be hooked up to the electrical grid via a 30 or 50 amp outlet at a campground, national park, or state park.

It could also be hooked up to the grid at home through a 15 or 20 amp power outlet.

On the road or at campgrounds without electrical hookups, the camper could be hooked up to an electrical generator.

30 and 50 Amp Hook-ups

As we discussed in our post “Do RV’s Need to Be Plugged In“, a camper usually has a 30 or 50 amp hook-up which allows it to be powered by the electrical grid, otherwise known as shore power.

Most smaller campers will have a 30 amp hookup while larger campers will have a 50 amp hookup.

While the camper is hooked up to shore power, it will automatically begin to charge the battery and run your electrical appliances at the same time.

It does this by sending power through the converter/inverter which then sends power to the 12-volt batteries as well as to the 120 VAC breaker panel.

For more information on how RV inverters and converters work, see our page about “How Do RV Inverters and Converters Work“.

The breaker panel will hookup to all of your AC outlets while the battery will hookup to any DC appliances.  If your battery were to completely die, you could still run all of your appliances off of AC outlets with the exception of the DC only appliances.

In most cases, the only DC only items you might have would be the overhead lights.

15 and 20 Amp Outlets

A battery can be hooked up to shore power with a home extension cord in the same way that it is hooked up with a 30 amp or 50 amp plug.  Alternatively, the battery could be taken out and charged with a 12-volt battery charger inside your home.

This is a popular method of charging small pop up camper batteries.

If your camper is small enough, you could put the camper inside your garage and you could place the 12-volt battery charger on your battery without having to take it off the camper.

Generators

Generators can also be used to charge your camper’s batteries.  Propane, diesel, and gas generators are popular among camper owners.  These generators are often hooked up just like shore power.

The generator would plug into your camper which will run your AC appliances directly and also charge your battery at the same time.  Your battery would still be able to power your DC lights while charging in this instance.

Charging A Battery Directly With DC Power

There are a few ways in which you can charge your battery without having to go through the converter first.  These charging methods will not simultaneously run AC appliances.

Instead, they’ll charge your battery which will then send power through your inverter so that it can power your AC appliances.

In this case, your battery would end up powering both your AC and DC appliances and lights while being charged at the same time.  Just note that powering AC appliances through a battery and an inverter is less efficient than powering them directly through shore power.

Also, you may find that charging your battery takes longer while your running appliances off of it.  In fact, if you run too many appliances, you may find that your battery doesn’t receive enough power to charge at all.

Alternator

One of the most popular ways of charging a 12-volt battery is by using a vehicle’s alternator.  This is how vehicles charge their own 12-volt batteries and it is often how motorhome house batteries are charged.

An alternator works by converting mechanical energy into electrical energy.  The mechanical energy is generated when the engine starts and a belt rotates the alternator.

Charging your batteries with an alternator is a great option for extended road trips.

Unfortunately, it is not a very good option for people planning to stay in one place for an extended period of time.  This is because you’d have to idle your vehicle to charge your batteries which is inefficient and not very good for your vehicle.

Solar power

Solar energy is becoming increasingly more popular among people with campers and motorhomes.  A solar power system starts with a solar panel which goes to an amp controller which then goes to the battery.  The amp controller can also go by the name charge controller.

A charge controller helps to keep the battery from overcharging.

There are two types of charge controllers for people to choose from.  The first type of charge controller is the pulse width modulation charge controller, otherwise known as a PWM controller.

Solar panels for your RV or Tiny House

The second type of charge controller is the maximum power point tracking charge controller.  You may have seen this type of charge controller referred to as an MPPT charge controller.

An MPPT charge controller is more efficient than a PWM controller but it can cost a little more to buy upfront.

Charge controllers come in different power levels.  These power levels are calculated in amps.  In order to charge a battery through solar power, you’ll need to have a charge controller with more amps than your solar panels and battery combined.

In order to calculate this, you just have to divide the watts provided by your solar panel by the number of volts in your battery bank.

Example
You have 300 watts of solar panels on your camper’s roof and two 12-volt batteries.

300/(12*2) = 12.5

With this number, you know that you’ll need a charge controller that can provide more than 12.5 amps of power to your battery bank.  In this case, you’ll most likely end up with a 15 amp charge controller.

This being said, I’d recommend you actually go with a higher amp charge controller than 15 amps.

The reason for this is that you might decide to add another 100-watt panel to your roof. 

After adding the panel, you’d end up with these numbers:

400/(12*2) = 16.6

If you’d only bought a 15 amp controller, you’d now have to buy another charge controller to charge your system.

Wind power

In some rare cases, people have used wind turbines to charge their camper batteries.  This is usually done by people who live in windy areas and who do not move their camper very often.

Charging a battery from the power of the wind works in the same way that charging a battery from solar does.

In this case, you’ll have a wind turbine which goes to a charge controller which then sends energy to your battery.

Some people have considered using wind turbines while driving but this is not efficient, safe, or even legal.  It isn’t efficient because it creates drag while towing and reduces fuel efficiency.

It isn’t safe since a turbine that is small enough to mount on a camper can’t handle the prolonged stress of driving and it isn’t legal because of safety reasons.

Related Questions

Can I charge my batteries from multiple sources at once?

Yes, you can charge your batteries from multiple sources at once without hurting your batteries.  For example, you could have your solar panels hooked up while you’re also hooked up to shore power.  Your system will protect your batteries from overcharging.

Can I overcharge my battery?

Yes, it is possible to overcharge your battery which is bad for the battery and can even be dangerous.  This is why it is important to buy the appropriate equipment before charging your batteries from any source.

Can discharging a battery too far ruin the battery?

Yes, batteries should never be run down past the manufacturer’s recommended percentages.  For example, most deep cycle marine batteries will have a reduced lifespan when drained below 50%.  Lithium batteries can generally be run down to about 20%.

A standard car battery may die after only being run down a few times.  This is why it is never a good idea to drive your car after your alternator has died.

In Summary

There are many ways to charge a camper’s battery.  Most people will take advantage of multiple sources of charging.  The way you charge your battery will depend on where you are using your camper and what you are using its battery to run.

No matter what system you use for charging your battery, always be sure to use the recommended charging tools or you will risk harming your battery.