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RV Converter & Battery Chargers | A Complete Guide

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If you’re planning to live in a van full time or even for a few weeks at a time, you’ve probably already got your solar setup worked out to keep the battery bank charged.

But what about when the weather is against you for days on end?

Watching the battery monitor and the overall battery levels fall as the clouds stubbornly refuse to lift is an indication to be more mindful about your electrical use.

Charging the batteries as you drive can give a boost but it’s not always practical to run the engine for long enough to get a decent charge.

The ability to recharge the battery bank from a mains supply or electrical hookup (EHU) is a perfect fall back position.

You can spend time on a campground with a hookup facility or top up the batteries from home.

An RV converter charger is an essential electrical component in the hook up installation to recharge batteries.

This post will help you understand the basics of power converters and battery chargers so you can decide what size you need and the key features to look out for when buying.

We’ve recommended our top picks of RV power converters and included an installation guide at the end of the post too.

Avoid any confusion: Campervan Converters v Inverters – What’s the Difference?

Build your own camper quick start guide

RV Power Converters & Battery Chargers | Our Top 5 Picks

Powermax Converter Charger
  • 3 stage charging & integrated cooling fan
  • Reverse polarity, overload and thermal protection
  • 2 year warranty
Progressive Dynamics Converter Charger
  • Accessory port
  • Low voltage & reverse polarity protection
  • Fast charging
Victron Smart Converter Charger
  • 93% efficiency
  • 7-stage charging process
  • Compatible with Lithium, Gel & AGM
CTEK Converter Charger
  • Reverse polarity protected
  • 10 amp
  • Reconditioning programme to restore battery life & recondition flat batteries
Numax Converter Charger
  • 12 month warranty
  • Suitable for 50 to 135Ah battery bank
  • Budget friendly

RV Power Converter vs Battery Charger | What’s the Difference?

All vehicles have a starter battery but these are quite different from deep cycle or leisure batteries.

If your car (or camper) has a flat starter battery, you could remove it and plug it into a standard automotive battery charger.

While these are perfect for using in a garage or at home, many aren’t ideal for fitting in an RV or camper. 

automotive battery charger

They’re often designed to be portable whereas for a camper, we want a component we can fit and forget, using as little space as possible.

Europeans refer to this component as a campervan battery charger. In the US, you’re probably heard it called an RV power converter.

They’re one and the same thing with the terms used interchangeably, depending on which side of the pond you’re from.

What does a Converter do in an RV?

RV Converter vs Inverter

In the most simple terms, a power converter changes AC power to DC power. But why would you need to?

Camper’s leisure battery banks can only be recharged with DC power. 

To take advantage of a mains hookup on a campsite or at home to top up the batteries, the mains supply must be converted.

Some RV owners have DC appliances but no battery bank. DC appliances cannot run directly off an AC power supply. 

The mains voltage must be stepped down and transformed from 110v or 240v AC to 12v DC first.

Some 12v appliances already have a kind of converter fitted. 

LED lights are a good example where the cable has a transformer pre-installed, so they can be wired to the mains circuit in your home. The transformer converts the AC power to DC before it reaches the bulbs.

It’s the same too with laptops. They have a transformer box between the end plugged into the mains supply and the end plugged into the device. That box is converting the AC supply to DC.

But most other DC appliances must have a DC power supply to run. 

Some RVs already have a converter installed. But if your camper isn’t one of them, the in-built converter has failed or you’re building a camper conversion, you can buy a separate power converter.

Need more advice and support on a specific part of your campervan electrics? Join our new Facebook Group to connect with a growing community of like minded van builders.

Why do I Need a Converter in my RV?

Solar battery bank Calculator

If you don’t have a battery bank in your camper and all your electrical appliances are the same as those you plug into a household socket, you don’t need a converter.

All the appliances will run from the campground mains supply.

If you have a battery bank and want the flexibility to recharge when you have access to a mains supply, a power converter or campervan battery charger is an essential piece of kit and a great addition to a camper’s battery charging system.

Some people use the power converter to directly run DC appliances when they’re hooked up.

While the converter does allow for this, we suggest:

  • If you have a battery bank, wire DC appliances to the battery not the converter. Then you can use them as the battery is being charged when on hookup, use them off grid and get away with a smaller converter too.
  • If you don’t have a battery bank, use AC appliances instead of DC alternatives wherever possible. They’re cheaper anyway and you won’t need to buy a converter. Without a battery bank you can’t use anything off grid either so this isn’t really a factor.
  • Without a battery bank, keep the amount of DC appliances to a minimum. You’ll need to install fuse blocks and switches between the converter and each appliance.

How Does a Converter Work?

AC power oscillates, changing direction between positive and negative voltages.

DC power travels in one direction, seemingly a straight line.

Basically a converter consists of a series of capacitors. These act as mini electron stores catching the AC power as it enters the converter.

Synchronised, they create a solid, flat line DC output.

How an RV Power Converter works

The converter then transforms this to the correct voltage, usually 12v for campervans, RVs and motorhome battery banks.

This is solid state technology (i.e. no moving parts) so converters tend to be quite reliable.

Different Types of Converters

There are 2 different types of converters used for battery charging:

  • Single Stage Chargers
  • Multi-Stage Chargers

What is a Single Stage Charger?

As the name suggests, a single stage charger has one cut in and cut off setting.

It pours a lot of amps into the battery and as the battery voltage climbs, this tapers off. 

It charges the battery until it reaches a specified “full” voltage then cuts out.

When the battery voltage drops below the cut off setting, it begins charging again.

The downside of these types of converters is they don’t always charge the battery fully, potentially shortening the life of the battery and they’re not compatible with some battery types, like lithium.

They can also take quite a long time to bring a battery upto a near full charge.

Single stage chargers are fitted to many RVs and motorhomes as standard.

When you’re buying a campervan, it’s worth checking what type is installed.

What is a Multi Stage Charger?

Sometimes called smart chargers or smart converters, a multi-stage converter is more effective at charging the battery bank.

Constantly responding to the state of the battery, the charger delivers the optimum amount of current to charge the battery as fast and as safely as possible.

There’s usually at least 4 stages:

  • Bulk |The converter delivers as much current as the battery will accept until about 80% charged
  • Absorption or cool down cycle | The converter lowers the input current and gradually brings the battery upto almost full charged
  • Float or trickle charge or maintenance charge | The converter trickles current into the battery, maintaining it at full charge
  • Equalize | Especially important for lithium batteries, this stage improves the overall battery capacity

There’s a few advantages these chargers have over the single stage chargers:

  • They can charge batteries much faster than a single stage charger so you don’t need to spend so much time and money hooked up
  • Most are compatible with lithium, AGM and Gel batteries
  • They’re better at protecting the long term health of the battery bank

Some camper battery chargers have even more stages than this and can include diagnostic checks, restoring completely dead batteries and more.

What Size Converter Do I Need in my RV?

Converter chargers are sized in amps.

In theory, the converter needs to be powerful enough to provide the total current you’ll draw down at any one time.

With a Battery Bank

A battery bank will draw a maximum current based on the manufacturer’s specification.

Look for the Maximum Charge Current on the spec.

As an example, let’s say you have a 200ah battery bank made up of 2 x 100ah Gel batteries and they’re half full. They each have a maximum charge current of 30 amps.

This means if you provide 30 amps each (so a 60 amp converter), they’ll take it.

A 60 amp converter will take less than 2 hours to fully recharge them, longer if you also have load on the batteries as they charge.

Going up a size gives some wiggle room for additional DC demand, though the batteries will still only take 30 amps each at most so won’t charge any faster. 

You can go with a smaller one and accept the batteries will take longer to charge.

If you do go smaller, make sure the minimum size is at least 10% of the total battery bank size. So if you have a 200ah battery bank, make sure your converter is at least 20 amps.

Without a Battery Bank

If you don’t have a battery bank or have DC appliances to connect directly to the converter as well, you need to calculate expected load.

Make a note of all your DC appliances and the amp rating of each. If only a power rating is given (watts), divide it by 12 volts to convert it to amps.

Add up the amps of the appliances you’re likely to use at the same time.

This is the minimum size power converter needed.

Battery Charging & DC Load

RV hookup to shore power

Let’s say you have 10 amps of DC appliances on top of the 2 batteries mentioned above and you want to use them all at the same time.

There’s no need to go any bigger than a 70 amp converter (60 amps for the batteries and 10 amps for the DC appliances). 

A smaller converter is ok too though the batteries will take longer to charge. And remember to make sure it’s at least 10% of the total battery bank.

Our battery bank is made up of 2 x 115h Gel batteries, each with a maximum charge current of 30 amps. We don’t connect any DC appliances directly to our 25 amp converter.

If the batteries are half full when we hook up, they recharge in around 5 hours, plenty of time to top up if we spend just 1 night in a camp with extremely low batteries.

It’s not an exact calculation because we have solar panels also charging and variable use of onboard DC appliances, but it gives you an idea.

What to Look for When Buying a Converter

There’s a lot of converters available on the market. 

Even once you’ve calculated the size needed, there’s other aspects of the component’s specification important to look at before making your final decision.

Input Voltage Range

This indicates the voltage of the mains supply needed to supply the converter.

In the US, this is probably 110-130v while in Europe and the UK is more likely to be 220-240v.

If you’re a global traveller, choose an input voltage to match the location you plan to spend most of your time or consider the few chargers that will accommodate a voltage range of 80 -250v AC.

We have a 240v battery charger (being from the UK) and when we hookup to a 110v supply (like in Brazil) we use a transformer.

We’ll cover transformers more in another post.

Output Voltage

This indicates the voltage the battery charger will supply the battery.

Most RV and campervan electrical systems have a 12v battery bank. Some have 24v and even fewer have 48v. 

Buy a converter with an output voltage to match your battery bank voltage.

Efficiency Rating

RV Converter & Battery Chargers hookup point

The greater the efficiency rating the less heat the charger generates when in use and the less current losses you’ll experience.

A higher efficiency rating also means it will draw less current from the hook up point.

Some campgrounds limit the current a camper or RV can draw from their electrical system hook up points.

The efficiency rating is especially important in these situations. 

We’ll try to illustrate this here.

Let’s say the campground has a 25 amp limit on its AC hookup point. This needs to supply your RV converter and all AC appliances on your mains circuit.

If a power converter is taking 7 amps, this leaves 18 amps for your microwave, TV, air conditioning and so on.

Take more than this and the circuit breakers will trip and you’ll lose all power.

If the hook up connection point is locked (common practice in Europe)  you’ll need to get the campsite staff to open up and reset the trip switch. 

A less efficient power converter may take 8 or even 9 amps, so reducing the amount of AC available before it trips.

No Load Power Consumption

When not connected to a mains supply, the converter isn’t receiving any power so is in effect switched off.

But once connected, even if the batteries are fully charged, the converter is on and uses some power.

Where the mains supply is limited, a smaller idle rate or no load power consumption level might be important.

It usually follows that a highly efficient converter has a low idle rate – maybe less than a 1 watt per hour.

Number of Outlets

Some converters allow DC appliances to be connected directly rather than wiring them to the battery.

The more outlets the converter has, the more appliances you can connect.

Maximum Charge Current

This indicates the maximum amps the unit can output. 

It’s what you size based on your batteries and load as described above.

Charge Algorithm

Multi stage battery chargers can have upwards of 3 stages controlling adaptive battery management. 

The charge algorithm indicates how many stages are in that battery management system.

Battery Compatibility

Not all power converters or battery chargers are compatible with every battery type so make sure to check before buying.

Safety Features

Power converters come with safety protection features, offering greater reassurance and protecting the van electrics.

They vary from device to device but here’s a list of common features:

  • Battery reverse polarity protection
  • Output short circuit protection
  • Over heating protection
  • Remote monitoring

The Best Campervan Battery Chargers & RV Power Converters

PowerMax Pm3-55 RV Converter Charger 

PowerMax Pm3-55 RV Converter Charger

PowerMax is a reputable brand in the US and this PM3-55 Power Supply Converter Charger is one of the most popular models.

Easy to install and including mounting brackets, it converts AC to 12v DC power to charge a battery and/or power 12V equipment. 

110v units are available in sizes ranging from 15 amps to 120 amps and 220v units in 55 and 75 amps.

It has 3 stage charging, LED indicators and is temperature controlled. 

PowerMax claim the cooling fan is quiet though some reviews suggest they can be a bit noisy.

Progressive Dynamics 70 amp Inteli-Power 9200 Series Converter 

Progressive Dynamics 70 amp RV Power Converter Charger

Another popular RV power converter is this 70amp unit from Progressive Dynamics. 

It can supply a reliable and filtered DC power to DC appliances and lighting circuits inside your RV and a rapid recharging to the battery bank.

It has and in built charge wizard constantly monitoring the battery bank for a safe and fast charge.

Victron Blue Smart IP22

Victron Blue Smart IP22 Battery Charger for RVs and Campers

As you might expect from a top brand like Victron, the Blue Smart IP22 is highly rated by users.

Compatible with Lithium, Gel & AGM batteries, the 7-stage charging process ensures a fast and safe recharge and quiet operation.

With a handy bluetooth function, you can control and monitor the condition of the charging from an app on a mobile device.

CTEK MXS 10 

CTEK MXS 10 Campervan Battery Charger

The CTEK MXS 10 is an 8 stage charger delivering 10 amps to 12v battery banks between 20-200Ah.

It can provide a maintenance charge for batteries upto 300Ah.

This battery charger has a good reputation for restoring virtually dead batteries too. 

It includes an analysis cycle which checks the batteries ability to hold charge and warns if the battery is nearing the end of its life.

The MXS 10 has a temperature sensor to optimise charging and can be used as a power supply source for DC appliances.

Complete with standard safety features, this is an excellent value battery charger for 220-240v mains supply.

Numax 12V 10A 

Numax 12V 10A Battery Charger

This budget friendly campervan battery charger is ideal for relatively small battery banks.

Suitable for batteries upto 135ah, it comes with a 12 month warranty too.

Fitted with a standard UK 3-pin plug, the Numax runs on 220v input voltage.

For the price of this budget friendly component, the Numax has excellent reviews for restoring overly discharged batteries.

RV Power Converter Wiring Diagram

RV Power Converter Wiring Diagram Battery Charger
RV Power Converter Wiring Diagram Battery Charger

How to Install a Power Converter in A Camper

Active Time: 30 minutes
Total Time: 30 minutes

No matter the size of your RV power converter the installation is generally the same. This guide shows you how to wire a battery charger in an RV, motorhome or camper.

Materials

Instructions

  1. Choose location for the converter
  2. Secure the converter to its operating position
  3. Connect the converter’s chassis earth point to the van’s earth point
  4. Connect DC -ve cable from the coverter to the -ve terminal of the battery
  5. Connect DC +ve cable from the converter to it’s designated fuse block input
  6. Connect the fuse block output to the +ve battery terminal
  7. Make sure there is no shore power hooked up to the RCB
  8. Connect the live, neutral and earth cables to the correct RCB terminals
  9. Insert fuse in the DC fuse block
  10. Connect hookup & check the RCB operates correctly with the test button
  11. Switch on converter 
  12. Using multimeter confirm input & output voltages are correct

Notes

  • The shore power hook up must already be installed before wiring up the battery charger
  • Make sure the RCB is correctly rated for the power converter
  • Make sure there is plenty of ventilation around the converter to help keep it cool when in operation
  • Position the converter as close to the battery as possible to minimise voltage loss
  • This how to guide provides an informative overview. Always follow the manufacturer’s installation instructions.
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