How to Connect Batteries in Series and Parallel: Tips and Precautions

A battery is an essential component of many electronic devices and renewable energy systems. They store energy that can be used when a primary source of energy is unavailable or insufficient. A single battery, however, may not provide enough voltage or capacity to power a device or system in some cases. To increase voltage or capacity, multiple batteries need to be connected in series or parallel. In this blog post, we will explain how to connect batteries in series and parallel as well as provide some tips and precautions.


Connecting batteries in series

If you connect batteries in series, you need to connect the positive terminals of one battery to the negative terminals of the next battery, and so on. In a battery bank, the battery bank’s output terminals are the positive and negative terminals of the first and last batteries. The voltage of the battery bank is the sum of the voltages of the individual batteries when they are connected in series. Two 12-volt batteries connected in series will produce 24 volts as the output voltage of the battery bank.

There are some precautions to take when connecting lithium batteries in series. Lithium batteries, especially lithium-ion batteries (Li-ion), are susceptible to overcharging and overdischarging, which can result in overheating or even explosions. A battery management system (BMS) must be used to balance the voltage of each battery in the series. The BMS ensures that each battery is charged equally and discharged equally by monitoring its voltage.

Connecting batteries in parallel

When batteries are connected in parallel, the positive terminals of each battery are connected to the positive terminals of the next battery, and so on, until all batteries are connected. Likewise, the negative terminals of all batteries are connected. In a battery bank, the output capacity is equal to the sum of the individual battery capacities. For example, two 100Ah batteries connected in parallel will generate 200Ah of output power.

It is also important to take precautions when connecting lithium batteries in parallel. Lithium batteries have different internal resistances, which can result in batteries discharging faster than others. In order to prevent this, lithium iron phosphate batteries (LiFePO4 or LFP) must have a lower internal resistance than other types of lithium batteries. In addition, batteries with similar capacities, ages, and manufacturers should be used.

Parallel and series connections of batteries

Additionally, batteries can be connected in series and parallel to increase the battery bank’s voltage and capacity. Several parallel banks are connected in series to create a bank with a higher voltage by connecting them in parallel to create a bank of higher capacity. This is referred to as a series-parallel configuration. Electric vehicles and renewable energy systems can use this configuration because it allows both higher voltage and capacity.


It is simple and effective to increase the voltage or capacity of a battery bank by connecting batteries in series or parallel. In particular, lithium batteries require special attention due to their sensitivity to overcharging and overdischarging. Therefore, following the precautions and guidelines can ensure safety and efficiency. You can create a battery bank that meets your energy needs and provides reliable and safe power by following these precautions and guidelines. Redway’s focus on custom lithium battery solutions enables them to meet the unique needs of their customers, and as a wholesale battery supplier, they provide B2B services for OEM/ODM projects.