A Forklift Battery's Internal Resistance: Why is it Important?

Posted by Heiwhite on November 10th, 2023

A battery's internal resistance is often called the "gatekeeper." Batteries are a source of voltage, but they all have an internal resistance that controls the voltage delivery and determines their runtime. A battery's internal resistance is determined based on a number of variables, including its size, its state of charge, the age of its cells, temperature, its internal chemistry, and its current discharge. The internal resistance is measured in milliohms. When you are aware of a battery's internal resistance, you can determine its state of health, power capabilities, and estimate its performance.

When measuring the internal resistance of a battery, there are two main purposes.

Inspecting batteries during production is one of the most important processes

Firstly, internal resistance is measured in order to ensure quality control throughout production. By measuring internal resistance, you can determine the quality of a battery.

When BSL electric forklift battery are produced, they are sent to a BSL automotive-grade module factory after factory inspection. Each incoming cell at the BSL factory undergoes an acceptance inspection before it is assembled into modules and battery packs because factors such as vibration during transportation and even time can cause defects. An equal internal resistance is crucial for a battery pack. If one or more cells have high internal resistance or have degraded, they will become a bottleneck and limit the battery pack's capacity. Using tests to monitor cell internal resistance simultaneously ensures consistent battery quality within specification. This is a crucial part of maintaining battery quality during production. A battery pack's quality can be improved by selecting cells with equal internal resistance


Battery maintenance is another reason to measure internal resistance. The internal resistance of a battery gradually increases as it is used. A battery's power is generated by a chemical reaction between its electrolytes and its electrodes. However, over a long period of time, the chemical reaction will slow down due to rust and corrosion inside the electrodes. As the chemical reaction slows down, the internal resistance of the battery increases.


A battery with a lower internal resistance is more capable of delivering more power, as already indicated. This is especially useful for electric forklifts and airport GSE. Batteries with high resistance, on the other hand, often heat up, causing the voltage supplied to drop under load, resulting in premature shutdown.

Here we discuss how internal resistance affects the performance of lift truck batteries, as well as ways to check internal resistance and mitigate some of its effects.


Forklifts are a common power tool in industrial applications that greatly benefit from batteries that have a low internal resistance. Forklifts are usually used for lifting and transporting heavy loads over short distances like in warehouses, which means they typically require a lot of power to raise the loads consistently. Most forklifts are fitted with batteries that have an exceptionally low internal resistance and can sustain high voltage for long periods of time. Thus, they are capable of lifting heavy loads and transporting them. Get more info about forklift battery suppliers.

Forklifts use lithium-ion batteries because they have a very low internal resistance, which remains relatively stable when fully charged and discharged. Forklifts can use this type of battery to lift loads and carry them to the required location since it continuously provides high current. Until the charge is depleted, lithium-ion batteries provide high current power, allowing them to run forklifts continuously in industrial settings.

However, lead-acid batteries have relatively low internal resistance, but they cannot maintain the high current required by forklifts for an extended period of time. Their voltage drops significantly after a couple of seconds, and they need to rest before they can give another burst.

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