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

If you’re installing more than one battery, you’ll need to understand the difference between wiring the batteries in series and parallel.

But what’s the difference between these two wiring methods, and why does it matter?

In this guide, you’ll learn:

• The benefits of wiring batteries in series vs. parallel
• Potential drawbacks of each method
• How to decide which option is best for your campervan’s electrical setup

You’ll also find detailed diagrams showing exactly how to wire your batteries in series, parallel, or even a combination of both.

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

If you plan to go off-grid in your campervan, RV, or boat, you’ll need at least one leisure battery. But if you’re installing multiple batteries, you’ll need to wire them together—and there are two ways to do this: series or parallel.

Here’s a quick example to show the difference clearly:

• Wiring two 100Ah, 12V batteries in series gives you 24V, 100Ah.
• Wiring two 100Ah, 12V batteries in parallel gives you 12V, 200Ah.

Both setups provide the same amount of power (watt-hours) but are arranged differently. To put it simply:

• Series: 24 volts x 100 amp-hours = 2400 watt-hours
• Parallel: 12 volts x 200 amp-hours = 2400 watt-hours

So, choosing series or parallel depends mainly on the voltage and capacity your electrical system needs.

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

1. Capacity (amp hours) – How much energy storage you’ll need.

If you plan on charging your batteries directly from an alternator (like in boats, RVs, or campervans), your battery bank voltage usually needs to match the alternator’s voltage. Most smaller vehicles and boats run on 12V systems, while some larger vehicles, boats, or off-grid cabins use 24V or even 48V systems. If you’re unsure, check the voltage of your starter battery or alternator.

To work out how much battery capacity (in amp hours) you’ll need, consider:

• Which appliances and devices you’ll be using
• How much power each device uses
• How long you’ll typically run each device
• How quickly and easily you’ll be able to recharge your batteries

Once you’ve got a clear idea of the voltage and capacity required, you’ll be ready to choose suitable batteries and decide how to wire them.

Battery Bank Voltage

Deep-cycle batteries come in several common voltages, including:

• 12V
• 24V
• 48V

12V Electrical Systems

In the past, many off-grid users chose 6V batteries because they were available with higher amp-hour capacities. To reach 12V, you’d wire two 6V batteries together in series.

Today, you can easily find powerful 12V lithium batteries with capacities of 200Ah or more, making them a simpler, more effective choice for most setups.

24V Electrical Systems

If your off-grid setup runs at 24V, your options are:

• Wire two 12V batteries in series, or
• Simply use a single 24V battery.

48V Electrical Systems

48V systems are becoming increasingly popular, especially for larger boats, off-grid cabins, or more energy-intensive setups.

48V batteries are now available commercially, but there’s a broader choice of 12v and 24v batteries. Instead of simply using a single 48V battery, you can still achieve 48V by wiring:

• Two 24V batteries in series, or
• Four 12V batteries in series.

Battery Bank Capacity

Once you’ve chosen your battery bank’s voltage, the next step is to decide on its capacity, measured in amp hours (Ah).

How many amp hours you’ll need depends entirely on your specific power usage and how quickly or regularly you can recharge your batteries.

Here’s an example to help clarify:

Imagine you have a 12V system and calculate that you need around 200Ah capacity. You have two common options:

• A single 12V, 200Ah lithium battery, or
• Two 12V, 100Ah lithium batteries wired in parallel (this doubles the amp-hour capacity without changing voltage).

If you choose lead-acid batteries (AGM or Gel), remember their usable capacity is only about 50%. To get a usable 200Ah, you’ll need to install around 400Ah total capacity (for example, two 12V, 200Ah AGM batteries in parallel).

Finally, always ensure all the batteries in your bank match the voltage, capacity, and type. Mixing different types or sizes can cause problems later on and shorten the lifespan of your battery bank.

How To Wire Batteries In Series

You’ll wire your batteries in series when you need to increase your battery bank’s voltage to match your chosen system voltage—for example:

• Two 12V batteries for a 24V system
• Two 24V batteries for a 48V system

Connecting batteries in series is straightforward: you simply connect the positive terminal of one battery directly to the negative terminal of the next. (Detailed diagrams showing exactly how to do this are included further down.)

The wiring diagram below shows two batteries wired in series.

The wiring diagram below shows four batteries wired in series.

Once connected, use a multimeter to check the total voltage. Measure from the positive terminal of the first battery in the series to the negative terminal of the last battery. You’ll notice the voltage adds up while the amp-hour (Ah) capacity stays the same as a single battery.

When wiring the battery bank into your system, connect it just like a single battery—positive from the first battery and negative from the last.

Advantages Of Connecting Batteries In Series

The main advantages of wiring batteries in series are directly related to the benefits of operating at higher voltages, such as 24V or 48V systems.

The most significant advantage is using thinner wires throughout your electrical setup.

Here’s why that matters:

• A higher system voltage means lower current (amps) flowing through your wires for the same power draw.

For example, consider a 400-watt device:

• A 12V system draws around 33 amps.
• A 24V system draws around 16 amps.

Lower current means thinner (and cheaper!) wiring. To illustrate:

• A 30-foot circuit carrying 33 amps (12V) would require thicker wires (around 4 AWG / 25mm²).
• The same 30-foot circuit carrying 16 amps (24V) would only need thinner wires (around 10 AWG / 6mm²).

Thinner wires reduce cost and simplify installation, especially important for larger off-grid setups like cabins, boats, or larger RVs.

A higher-voltage system (24V or 48V) can also make charging your battery bank more efficient. For example, a single 50A MPPT solar charge controller can handle twice the solar wattage at 24V compared to 12V, further saving on cost and complexity.

Disadvantages Of Wiring Batteries In Series

The disadvantages of wiring batteries in series relate specifically to operating your electrical system at higher voltages

Most off-grid appliances and devices—like lights, fridges, water pumps, and USB outlets—are designed to run on 12 volts. These 12V appliances are easy to find, affordable, and widely available.

If you create a higher-voltage battery bank (like 24V or 48V), sourcing compatible DC appliances becomes more difficult and expensive.

You can still use standard 12V devices, but you’ll need an extra component called a step-down converter to lower the voltage from 24V or 48V back down to 12V.

How To Wire Batteries In Parallel

You’ll typically wire batteries in parallel when you want to increase your battery bank’s total capacity (amp-hours) without changing the system voltage.

Connecting batteries in parallel is straightforward: you connect all positive terminals together, and all negative terminals together.

The wiring diagram below shows two batteries wired in parallel.

The wiring diagram below shows four batteries wired in parallel.

Once your batteries are connected, use a multimeter to confirm the voltage. Simply measure from the positive terminal of one battery to the negative terminal of another battery in your parallel setup. The voltage will remain the same as a single battery, but your total amp-hour capacity will be the sum of all batteries connected.

When hooking up your battery bank to your off-grid system, just treat the parallel battery bank as if you’re connecting a single battery—take the main positive connection from one battery and the main negative connection from another battery in your parallel bank.

Advantages Of Connecting Batteries In Parallel

The main advantage of wiring batteries in parallel is that you can easily increase your battery capacity (measured in amp-hours) without changing your system’s voltage.

Adding another identical battery in parallel effectively doubles your available capacity. If your off-grid system runs at 12 volts, for example, adding more batteries in parallel means you don’t need to switch to expensive, harder-to-find 24V appliances. You can keep using your standard 12V devices, making life simpler and cheaper.

Another practical benefit is that a parallel setup is easily expandable. If you discover you need more power storage down the road, you can just add another identical battery in parallel.

Plus, if one battery in a parallel bank fails, you can remove it and continue using your system—albeit at a slightly reduced capacity. With batteries wired in series, losing one battery means the whole bank stops working because the system requires the combined voltage.

Disadvantages Of Connecting Batteries In Parallel

The main downside of wiring batteries in parallel is that you’ll need thicker cables. This is because adding more capacity increases the amount of current flowing through your system. Higher current means you need thicker—and more expensive—wires.

This can be tricky if you want to run powerful appliances (like air conditioners or heaters) at low voltages, such as 12V. To use these appliances easily, you’d probably need dedicated AC circuits powered by shore power, an inverter, or a generator.

Can I Increase Battery Capacity When Wired In Series?

Absolutely—although wiring batteries in series alone doesn’t increase capacity, you can still increase the total capacity by combining multiple series-wired battery groups together in parallel.

It might sound complicated, but it’s actually pretty simple. Let’s break it down clearly with an example:

Say you want a 400Ah capacity for a 24V system using 12V batteries. You’d:

• Wire two 200Ah 12V batteries in series, giving you 200Ah at 24V.
• Wire another two 200Ah 12V batteries in series, again creating another 200Ah at 24V bank.
• Then, these two series groups are wired in parallel. This doubles the capacity, giving you a total of 400Ah at 24V.

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

Charging Batteries in Series Vs. Parallel

No matter how your battery bank is wired, you’ll typically charge it using one or more of these devices:

• MPPT Solar Charge Controller charges the battery from energy harvested by solar panels
• DC to DC Charger (aka B2B Charger) charges the battery from the vehicle’s engine
• Battery Charger (aka Converter) charges the battery from shore power or a generator

Regardless of whether your batteries are in series or parallel, the charging method stays the same. Just ensure the charger matches your battery bank’s voltage and battery chemistry (e.g., lithium, AGM, etc.).

Connect your charger by:

• Connecting the charger’s positive cable to the positive terminal of the first battery in the bank.
• Connecting the charger’s negative cable to the negative terminal of the last battery.

How Many 12 Volt Batteries Can You Run In Parallel?

Wiring batteries in parallel is a great way to increase your total battery capacity (amp-hours). There’s no strict limit on how many batteries you can wire in parallel, but most manufacturers suggest a maximum number.

For example, Renogy recommends wiring no more than eight of their 200Ah lithium batteries in parallel. Eight batteries would provide 1600Ah, which is usually far more capacity than most off-grid cabins, RVs, or boats need.

Just remember:

• Four 12V, 100Ah batteries in parallel = 400Ah at 12V total capacity.
• The larger your battery bank, the longer it’ll take to charge fully. Always keep this in mind when sizing your system.

How Many 12 Volt Batteries Can You Run In Series?

You can wire as many batteries in series as you like, but keep in mind every battery you add increases the system voltage, not the capacity.

For instance:

• Two 12V, 100Ah batteries wired in series create a 24V, 100Ah battery bank.
• Four 12V, 100Ah batteries wired in series create a 48V, 100Ah battery bank.