Wiring RV Batteries In Series Vs. Parallel: Everything You Need To Know

Graham Bogie

Get the most out of your RV – understand the difference between wiring RV batteries in series vs. parallel. Learn all you need to know in this comprehensive guide.


Knowing how to wire RV batteries correctly is crucial to ensure your RV’s electrical system operates efficiently.

When it comes to wiring batteries, there are two main methods: wiring them in series or parallel.

But what exactly is the difference between these two methods? And does it even matter which one you use?

This guide explains everything you need to know about wiring batteries in series vs. parallel.

We’ll cover topics such as:

  • the benefits of each method,
  • potential drawbacks,
  • and more.

So, read on for a comprehensive understanding of wiring RV batteries!

What’s The Difference Between Wiring RV Batteries In Series Vs. Parallel?

When you own an RV, camper, or motorhome and want to use your electrical system off-grid, you need at least one battery.

If you have more than one battery, they need to be wired together in series or parallel.

We can increase the voltage by wiring batteries in series, but it doesn’t affect the amp hour size.

We can increase the capacity (amp hours) by wiring batteries in parallel, but it doesn’t affect the voltage.

So, for example:

  • if we wire 2 x 100 amp hour 12v batteries in series, we will have a 100ah, 24v battery bank.
  • if we wire 2 x 100 amp hour 12v batteries in parallel, we will have a 200ah, 12v battery bank.

Both configurations provide the same power because watt-hours = volts x amp hours.

So, in the above example, both configurations will provide 2400 watt-hours.

How Do I Know If I Should Wire RV Batteries In Series Or Parallel?

Before you can decide how to wire your batteries, you should determine:

  • What voltage you need, and
  • How much capacity (amp hours) you need.

Assuming you want to charge your batteries while driving, it is best to stick to the same voltage as your alternator. Most RVs are 12v, but some are 24v. Check the voltage of your starter battery if you’re unsure.

How much battery capacity you need (measured in amp hours) depends on the following:

  • what kind of appliances you use,
  • how power-hungry they are,
  • how long you’ll use them, and
  • how effectively you can recharge the batteries.

Once you understand the capacity and voltage required, you can shop for batteries.

When you buy RV batteries, you need to consider their voltage and capacity.

Battery Bank Voltage

Deep-cycle batteries are available in a variety of voltages, including:

  • 6v
  • 12v
  • 24v

For 12v RV Electrical Systems

In the past, manufacturers typically produced 6v batteries in a higher amp hour capacity than their 12v alternatives. That made them an attractive option for RVers.

Today, manufacturers sell 12v lithium RV batteries in sizes over 200ah, so they’re usually a better option.

If you want to use 6v batteries in a 12v RV electrical system, you will need to wire pairs of batteries in series. Each pair of 6v batteries wired in series will provide 12v.

Alternatively, use a 12v battery.

For 24v RV Electrical Systems

Similar to combining 6v batteries to create a 12v battery bank, you can wire pairs of 12v batteries in series to create a 24v battery bank.

Alternatively, use a 24v battery.

For 48v RV Electrical Systems

48v systems are less common but not unheard of. You can’t buy 48v batteries, but you can create a 48v setup by either:

  • Wiring a pair of 24v batteries in series, or
  • Wiring four 12v batteries in series.

Battery Bank Capacity

Once you’ve determined the voltage of your battery bank, it’s time to choose the capacity.

Storage capacity is measured in amp hours.

How many usable amp hours you need depends on how much energy you’ll use and how often or quickly they will be recharged.

The amount of storage capacity (measured in amp hours) you need depends on how much energy you’ll draw from the batteries and how often or quickly they will be recharged.

Let’s say you have a 12v system and need 200ah capacity.

You can achieve this by installing the following:

  • a single battery set up i.e. 1 x 12v 200ah lithium battery, or
  • a dual battery setup i.e. 2 x 12v, 100a lithium batteries wired in parallel.

Remember, wiring in parallel increases the amp hours for the same voltage.

Note that the usable capacity of lead-acid batteries is about 50%. So, if you need 200ah, install 400ah AGM or Gel batteries wired in parallel.

All batteries in the combined battery bank must be the same voltage and capacity. If you mix and match, you may end up with problems best avoided.

How To Wire Batteries In Series

You need to wire batteries in series if you’re using:

  • 6v batteries in a 12v or 24v system, or
  • 12v batteries in a 24v or 48v systems, or
  • 24v batteries in a 48v system.

Wiring batteries in series is as simple as connecting one battery’s positive terminal to the negative terminal of the next battery in the series.

The wiring diagram below shows two batteries wired in series.

two RV batteries wired in series

The wiring diagram below shows four batteries wired in series.

four batteries wired in series

Once connected, use a multimeter to measure the voltage across the battery bank.

You measure it between the first battery’s positive terminal and the last battery’s negative terminal in the series.

Remember, the voltage is combined in each case, and the AH capacity remains the same.

You connect the first battery’s positive terminal and the last battery’s negative terminal to the RV electrical systems in the same way as if you were connecting a single battery.

Advantages Of Connecting Batteries In Series

The main advantage of wiring batteries in series is that you can use thinner wires throughout your camper’s electrical system.

Without getting too geeky, the higher the system voltage, the lower the current for the same device over the same length circuit.

So,

  • a 400w device running on a 12v system will draw a little over 30 amps, and
  • a 400w device running on a 24v system will draw a little over 15 amps.

To illustrate the difference in wire size,

  • the 30 amp current on a 30-foot circuit needs 4 AWG, 25mm² wire, while
  • the 15 amp current on a 30-foot circuit needs 10 AWG, 6mm² wire.

The thinner wire sizes become even more critical in large RV electrical systems, saving costs and space.

A battery bank wired in series is the best chance of running large appliances, like air conditioning units, when boondocking.

The other cost-saving advantage is when it comes to charging the battery bank from a large solar panel setup.

A 50A MPPT charger can cope with up to 600w of solar panels on a 12v battery setup. But that same charger could handle 1200w on a 24v battery setup.

Disadvantages Of Wiring Batteries In Series

All your DC appliances that run off the RV batteries must run on the same voltage as the battery bank.

Most RV electrical accessories run on 12 volts. Appliances like 12v TVs, fans, refrigerators, water pumps, lights, etc., are widely available.

If you’ve wired your 12v batteries in series to create a 24v system, those appliances become more challenging to source and are generally more expensive.

You could run 12v devices on a 24v system, but you’ll need a step-down transformer to convert the 24v DC power to 12v DC power.

Note: Some lithium batteries are not compatible with wiring in series. Always check the specification before you buy.

How To Wire Batteries In Parallel

You need to wire batteries in parallel to increase battery capacity.

Wiring batteries in parallel is as simple as connecting one battery’s positive terminal to the positive terminal of the next battery and the negative terminal to the negative terminal of the next battery.

The wiring diagram below shows two batteries wired in parallel.

two batteries wired in parallel

The wiring diagram below shows four batteries wired in parallel.

four batteries wired in parallel

Once connected, use a multimeter to measure the voltage across the battery bank.

You measure it between the first battery’s positive terminal and the last battery’s negative terminal in the battery bank.

Remember, the voltage should remain the same in a parallel circuit, and the AH capacity is multiplied by how many batteries.

You connect the first battery’s positive terminal and the last battery’s negative terminal to the RV electrical systems in the same way as if you were connecting a single battery.

Advantages Of Connecting Batteries In Parallel

The main advantage of wiring batteries in parallel is increased capacity.

Adding another battery of the same type and size in parallel doubles the capacity while keeping the same system voltage.

That means you can keep using your existing 12v appliances, like a 12v TV, without buying expensive 24v equipment.

Plus, you can expand it further by adding more batteries in the future.

The other advantage is that you can remove a battery if one fails. Then you can still use the power from the remaining batteries, albeit with reduced capacity. 

That’s impossible with two batteries wired in series, as your entire electrical system requires a higher voltage.

Disadvantages Of Connecting Batteries In Parallel

A parallel connection needs thicker cables because the current rating is higher than series connections.

That’s not always practical in an RV, so running large power appliances at low voltages is difficult.

The only realistic option to run appliances like air-conditioning units is to use dedicated AC circuits on either shore power or a generator.

Can I Increase Battery Capacity When Wired In Series?

Yes!

While wiring batteries in series doesn’t affect capacity, you can combine one group of batteries wired in series with another by wiring the two groups together in parallel.

Sounds complicated? It’s not.

Let’s say you want a 400ah battery capacity on a 24v electrical system using 12v batteries.

You need to:

  • wire 2 x 200ah 12v batteries in series to give 200ah at 24v
  • wire another 2 x 200ah 12v batteries in series to give 200ah at 24v
  • wire the two groups of 200ah at 24v in parallel to give 400ah at 24v.

Here’s the wiring diagram using parallel connections to combine sets of batteries wired in series.

two sets of batteries wired in series, wired in parallel

Charging Batteries in Series Vs. Parallel

There are three different charging components you can use to charge a battery bank:

When choosing each battery charger, ensure it’s rated the same as the battery voltage and is compatible with the type of battery.

So long as you use chargers rated the same as the voltage of your battery bank, there is no difference in how you connect them.

  • Connect the charger’s positive cable to the positive terminal on the first battery,
  • Connect the charger’s negative cable to the negative terminal on the last battery.

How Many 12 Volt Batteries Can You Run In Parallel?

For RV campers, wiring batteries in parallel is a great way to increase capacity. The more capacity you have, the more time you can spend off-grid.

There’s no limit to how many batteries you can wire in parallel, but check with the battery manufacturer.

For example, Renogy has a limit of wiring 8 of their 200ah lithium battery in parallel. Now that would be a huge 1600ah battery bank – a lot more than a regular RV would ever need.

so ensure the total capacity is reasonable for your needs.

For example, if you have four 12v 100ah batteries wired in parallel, the total capacity of the battery bank will be 400ah (100Ah x 4).

But remember, a larger battery bank will take longer to charge too.

How Many 12 Volt Batteries Can You Run In Series?

You can wire as many batteries in series as you like, but the system’s voltage will increase.

For example, if you have two 12v 100ah batteries wired in series, the total voltage of the battery bank will be 24v (12v + 12v).

The capacity of the battery bank will remain.

That said, regulations stipulate that the maximum voltage for RVs, campers, and motorhomes doesn’t exceed 48v. 

Important note: not all lithium batteries can be wired in series. Always check the manufacturer’s instructions before connecting batteries in series.

Graham Bogie

Graham Bogie - Expert in RV & Campervan Electrics - Mowgli Adventures

Graham is a seasoned marine electrical engineer with two decades of experience designing customized electrical systems for plant machinery and converting campers and overland vehicles. His expertise has led him to author the reputable Campervan Electrics Handbook and become the chief designer of our Campervan Electrical Design Service. As a knowledgeable figure in the field, his YouTube channel, blog, Facebook group, and newsletter, offering electrical advice and product reviews, reach more than a million users each year.

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