How To Connect Two 12 Volt Batteries In Parallel & Series?

If you are familiar with the function of a 12V 100Ah LiFePO4 battery, but you would like the LiFePO4 battery pack more powerful for your devices to increase the voltage and capacity by connecting in series and parallel. Connecting batteries in parallel and series is an effective solution, giving your customers with better experience. Your various applications, such as solar power systems, uninterruptible power supply systems, golf carts, and RV camps are equipped with modular battery pack in parallel and series. We share the guidelines you how to connect two 12 volt batteries in parallel and series.

What Does Connecting Batteries in Parallel and Series Mean?

Connecting batteries in series and parallel means increasing the voltage or capacity of a battery system. When wiring batteries in parallel, their voltages remain the same, but their capacities are increased. For example, connecting two 12V batteries with a capacity of 100Ah will give you a 12V battery with a capacity of 200Ah. In contrast, when wiring batteries in series, their voltages are increased but the capacity remains constant. Therefore, connecting the same two 12V batteries will give you a 24V battery with a capacity of 100Ah. This is the difference between series and parallel connections in the battery.

The total available energy (watt-hours) is the same no matter how the batteries are connected. Because the watt-hours are calculated by multiplying voltage by capacity. The total complete energy for both systems is 2400 watt-hours.

It is important to note that battery connection in parallel and series settings should have the same voltage and capacity ratings. Mixing and mismatching voltages and capacities would cause the batteries damaged.

Be sure to have the necessary tools and accessories, such as battery cables (positive and negative), wire cutters/strippers, wrenches or socket wrenches, safety glasses, and gloves on hand before making parallel and series connections. In addition, please make sure you work in a well-ventilated area to avoid inhaling any harmful gases that may be emitted during the process.

How to Connect Two 12 Volt Batteries in Parallel?

A 12-volt system includes two or more 12-volt batteries connected in parallel (positive to positive, negative to negative). This configuration increases the battery capacity (Ah) while keeping the voltage the same. The battery wires should be the same length for parallel connections which ensures the working current is the same for each battery pack. Parallel connections are common where higher current requirements or longer run times are required. Examples are in applications such as RVs, marine, golf carts, and backup power.


As shown in Figure 1, the negative terminal of the first battery is connected to the negative terminal of the second battery, and the positive terminal is also connected to the positive terminal. Connecting two 12-volt batteries in parallel means paralleling two 12V 100Ah batteries into one 12V 200Ah battery.

What Are The Advantages of Connecting Batteries in Parallel?

The benefits of paralleling batteries are as follows: If one of the batteries becomes empty or has a malfunction, the remaining batteries in the system can still deliver power. It is feasible to increase the system’s possible runtime while preserving voltage. Because amp-hour capacity accumulates, connecting two batteries in parallel may double runtime, three batteries can triple runtime, and so on.

Parallel-connected batteries have a lower system voltage than series-connected batteries for higher current applications. As a result, more current requires larger cables and a bigger voltage drop.

When running at lower voltages, larger electrical devices and power generators are more difficult to operate and less efficient.

How to Connect Two 12 Volt Batteries to Make 24 Volts?

How to connect two 12-volt batteries to make 24 volts is requested to connect them in series. It means you connect the positive terminal of one battery to the negative terminal of the next battery. Continue connecting batteries in this manner until all batteries are connected. The final connection should be the positive terminal of the last battery to the negative terminal of the first battery. At CM Batteries, our modular battery packs allow up to 4 pieces of lithium batteries to be connected in series to create a 48-volt system. Make sure you do not exceed its recommended limit for the number of batteries connected in series.

The total voltage of the battery pack will be the sum of the voltages of the individual cells. In this case, the voltage of the battery pack will be 24 volts. As shown in Figure 2, you can see two 12V 100Ah lithium iron phosphate batteries connected in series.

As shown in Figure 1, you can see two 12V 100 Ah LiFePO4 batteries connected in series. When the positive terminal of the first battery is connected to the negative terminal of the second battery, the batteries are connected in series. This means that the voltages of the batteries are added together, resulting in a total system voltage of 24 volts. The capacities of the batteries remain the same, so the total system capacity is 100 Ah.

Figure 2

What’s The Benefits of Wiring Two 12 Volt Batteries to Make 24 Volts?

  • When two batteries are wired in series, the batteries are not all connected to the same voltage source. This helps prevent overcharging or over-discharging of the batteries, which can damage them and increase the risk of fire.
  • If you are using the battery pack to power a 24-volt device such as a solar panel or an RV, connecting the batteries in series will give you the voltage you need.
  • Connecting two batteries in series helps reduce the cost of your battery system. This is because you can use fewer batteries, saving on the initial purchase price as well as maintenance and replacement costs.
  • A greater system voltage requires less current to power a device. This can be beneficial in a variety of ways. It can, for example, lower the size and expense of the wiring, as well as the amount of voltage drop in the system.
  • A higher system voltage also means that a larger amount of power can be delivered to the batteries during charging. This can be helpful if you are using a solar charger or another type of charger that is limited by its amperage rating.
  • Increasing the system voltage can enhance the efficiency of the battery bank. This is due to the batteries’ ability to run at a lower current.

Here is an example of how the benefits of running batteries in series can be applied to a real-world situation.

  1. A 360-watt device operating at 12 volts will draw 30 amps. This means that the wiring in the system must be able to carry 30 amps of current without overheating or causing a voltage drop. If the same device ran at 24 volts, it would only draw 15 amps of current. This would allow the use of thinner wiring, which would save money and make the system more compact.
  2. An MPPT solar charge controller rated at 50 amps can only handle 600 watts of solar power at 12 volts. However, at 24 volts, the same controller can handle 1200 watts of solar power. This means that a more extensive solar array can be used to charge the batteries, increasing the amount of energy available to the system.

However, it should be noted that there are some disadvantages to connecting two 12 volt batteries in series. Because it is more complicated than parallel, the batteries need to be connected in the correct order to ensure that the voltages add up correctly. If the batteries are not wired correctly, there is a risk of damage to the batteries or equipment powered by the battery pack.

What Are The Best Methods for Connecting 12 Volt Batteries in Series and Parallel?

Connecting batteries in series and parallel may look complicated, don’t worry, we will guide you step by step.

The first step is that you must first confirm the voltage of the battery pack you need.

I will use 24 volts as an example: As shown in Figure 3, the 4 CMB 12V 100Ah LiFePO4 batteries are divided into 2 strings of 2 batteries each, connected in series. This gives you two 24V 100Ah battery packs.

Figure 3

Then we’re going to connect the 2 series in series and parallel by connecting the positive terminal to the positive terminal and the negative terminal to the negative terminal. As shown in Figure 4, two batteries are connected in series to get 24V and then two 24V 100Ah battery packs are connected in parallel to get a 24V 200Ah battery pack. Keep in mind to double-check all connections, make sure fittings are secured and tightened, and verify voltage and capacity readings with a multimeter before using the battery setup.

Figure 4

FAQ for Connect Two 12 Volt Batteries in Parallel&Series

Q1: Can I connect batteries of different capacities or sizes?

A: No. Because it will cause the uneven discharge of the battery and may damage the weaker battery.

Q2: Is it safe to connect batteries in parallel or series?

A: Yes, be sure to follow the tips in this guide to stay safe. However, connecting batteries in series may raise the voltage to dangerous levels, so be sure to wear eyeglasses and gloves when connecting them.

Q3: What are the limits to parallel and series connections?

A: This depends on the type of battery connected. The limitation of the CMB 12V 100Ah LiFePO4 battery is the max 4 series connection and limited parallel connection.

Q4: Which connection option is better for my application?

Batteries for RVs, golf carts, and trolling motors are all suitable for parallel connection to increase the voltage and provide more power. CMB specializes in custom battery packs, click here to get the guide for your application.


We must re-emphasize following the necessary safety precautions and having the proper tools and materials given during the connection process. If you have any specific requirements or confusion about how to connect two 12-volt batteries in parallel or series, or any other questions, CMB’s professional engineers will guide you to how to connect two 12 volt batteries in parallel and series. Connecting 12V batteries in parallel and series increases the voltage and capacity in your battery system.


Leave a Reply