Electric Cars Still Use 12V Batteries: Functions and Signs of a Weak Battery

TANGERANG, Jakartaweekly.com – Battery electric vehicles (BEVs) still use a 12-volt battery, also known as an auxiliary battery, alongside the main battery that powers the vehicle.

Yandi Hermanto, Product Manager at GS Astra, explained that the 12V battery is an important part of an electric vehicle’s electrical system. The battery serves a different purpose from the main battery used to power the vehicle.

“Clearly, it is a fact that electric vehicles also use a 12V battery,” Yandi said in Tangerang on Saturday, September 26, 2026.

According to Yandi, electric vehicles have a main battery as their source of propulsion power, while the auxiliary battery supports various electrical functions in the vehicle.

In his presentation, Yandi also noted the significant growth in electric vehicle adoption. Based on data presented during the session, MOBIT Mestrik recorded 141% growth between 2020 and 2025.

A Faulty 12V Battery Can Prevent an Electric Car from Operating

The auxiliary battery is more than just an additional component in an electric vehicle. It plays a role in supplying power to the vehicle’s electrical systems.

Septian Aditya, Senior Expert Product Engineering at PT GS Battery, explained that when the auxiliary battery encounters a problem, the vehicle’s electrical system can be disrupted. This can ultimately prevent the electric vehicle from operating.

“When there is a problem with the auxiliary battery, the electrical system is automatically disconnected. As a result, the EV will not be able to operate,” Septian said.

According to him, several vehicle functions, including the door locks and head unit, also rely on the electrical system.

This shows that problems with an electric vehicle are not necessarily related to its main battery. A problem with the 12V battery can also cause the vehicle to lose certain functions and eventually become inoperable.

Not Every 12V Battery Is Suitable for an Electric Vehicle

Septian said electric vehicle owners should not replace their 12V battery arbitrarily simply because another battery appears to have similar dimensions.

Several parameters need to be considered. The first is the battery capacity, measured in ampere-hours (Ah), required by the vehicle.

The second is the battery’s dimensions, including its length, width, and height. These dimensions must match the available space and battery mounting position in the vehicle.

The third is the polarity, or the position of the positive and negative terminals. According to Septian, the polarity configuration must match the vehicle to ensure proper connection to its electrical system.

The use of a battery specifically designed for electric vehicles is also an important consideration.

“For electric vehicles, the battery must be specifically designed for electric vehicles,” he said.

Therefore, vehicle owners need to check the battery specifications before replacing the unit, rather than simply considering whether it can physically be installed in the vehicle.

Recognizing the Signs of a Weak 12V Battery

Yandi explained that there are several signs electric vehicle owners can look for when the 12V battery begins to lose performance.

One of them is a warning appearing on the vehicle’s instrument panel. Another sign is that the vehicle may have difficulty entering Ready mode, preventing the vehicle’s main computer from functioning properly.

Problems may also occur with the keyless entry and door-lock functions.

“So, those are the signs that the 12V battery is starting to weaken,” Yandi said.

According to Yandi, these conditions should be taken seriously by vehicle owners because a severely depleted or faulty 12V battery can prevent the vehicle from being used, even when the main battery still has sufficient charge.