12V Battery in Electric Cars: Its Role and Maintenance

Your electric car refuses to start even though the traction battery is fully charged? The screen remains black, and the doors won't open? The culprit is hiding under the hood: the 12V battery. This small lead-acid battery remains essential for the operation of any modern electric vehicle. Without it, you cannot access your car or activate the safety systems, even with a fully charged high-voltage battery.

Discover and try our app

Exclusive price and features

Rated 4,5/5 by users

Download the app

Why Does an Electric Vehicle Have a 12-Volt Battery?

Electric cars have two distinct batteries. The high-voltage traction battery (400 to 800 volts) powers the electric motor with a capacity of 40 to 100 kWh. Meanwhile, the 12V auxiliary battery manages all the vehicle's equipment and systems. This architecture meets safety requirements: using high voltage directly for accessories would be dangerous.

A DC/DC converter transforms high-voltage energy into 12-volt current, replacing the alternator in internal combustion vehicles. This system powers the 12V battery, which distributes electricity to the equipment: starting and unlocking system, computers, multimedia screen, air conditioning, LED lighting, and USB ports. The converter maintains the charge of the auxiliary battery as long as the main battery retains more than 20% capacity.

Common Breakdowns: Understanding to Better Prevent

The lifespan of a 12V battery in an electric vehicle is 3 to 4 years, compared to 5 to 6 years in a thermal model. This difference is explained by the constant demands of electronic systems. Unlike combustion engines, where starting briefly stresses the battery, electric vehicles maintain constant consumption for connectivity and battery monitoring.

The DC/DC converter automatically shuts off below 20% high-voltage charge to preserve range. The 12V battery is then no longer recharged and gradually discharges. Auxiliary battery failures are a frequent cause of breakdowns in electric vehicles, often just after flat tires.

Diagnosis and Maintenance: Best Practices

Checking the Health of Your Battery

The voltage of a healthy battery ranges between 12.6 and 13 volts at rest. Between 12 and 12.2 volts, recharging is necessary. Below 12 volts, replacement is required. A multimeter is sufficient for this monthly check, which can prevent many inconveniences.

Recharging Safely

To recharge safely, use a smart charger compatible with AGM. First, disconnect the negative terminal, then the positive. After 6 to 12 hours of charging, depending on the capacity, reconnect starting with the positive. In case of emergency jump-starting, connect the positive terminals together, then the negative to a metal ground. This procedure prevents damage to sensitive electronic systems.

Checklist of Symptoms of a Failing 12V Battery

Doors no longer open remotely
Multimedia screen is slow or black
"Low auxiliary battery" message
Vehicle refuses "Ready" mode
Interior lighting is dim

Choosing the Right Replacement Battery

Three technologies are used in electric cars. AGM batteries dominate the market with their excellent resistance to charge/discharge cycles and a price of €150 to €250. GEL batteries offer better longevity (5 to 7 years) for €200 to €350. LiFePO4 batteries represent the future with 8 to 10 years of service but cost €400 to €800.

Strictly respect the original capacity (35-75 Ah) and starting power (400-800 A). Check the dimensions and terminal positions before purchasing. On some premium models, replacement requires coding via the diagnostic interface.

Optimizing Lifespan: Our Tips

Regular use is the best prevention. Drive at least 30 minutes weekly to maintain the charge via the converter. For prolonged storage, charge the high-voltage battery to 50-60% and disconnect the 12V battery or use a trickle charger.

Annual maintenance, including a voltage test, terminal cleaning, and DC/DC converter check, significantly extends the lifespan. Absolutely avoid leaving equipment on when the engine is off or ignoring system alerts.

The 12V battery remains vital for your electric mobility. Its regular maintenance ensures optimal operation of all systems. At Electra, our fast-charging stations keep both your batteries in perfect condition for worry-free mobility.