Maintenance and Repair of 12V Auxiliary Batteries
What is the Purpose of Auxiliary Batteries in Hybrid and Electric Vehicles?
Auxiliary batteries in hybrid and electric vehicles power essential low-voltage components. These batteries are needed for powering vehicle computers, infotainment, lighting, power windows, and many other electrical systems.
The auxiliary battery is also responsible for engaging the main high voltage relays, which powers up the high voltage system into “Ready” or “Drive” mode by connecting the traction battery. If the auxiliary battery is flat or faulty, the vehicle will not power up!
Unlike conventional lead-acid starting batteries, auxiliary batteries are generally of AGM (Absorbent Glass Mat) or EFB (Enhanced Flooded Battery) types due to the need for high discharge/charge cycle durability.
Signs of a Faulty Auxiliary Battery
If you notice any of the following signs, it is important to resolve them quickly to avoid any further issues:
- Error codes or messages on the dashboard or infotainment system.
- Weak lighting or slow operation of windows, sunroofs, and power tailgates.
- Unusual or non-function of any electrical system accessories.
If your vehicle displays any of the above symptoms, we recommend that you have your auxiliary battery tested or replaced by a NexDrive technician and that you have the charging system verified. This requires professional equipment, as the high-voltage section of the vehicle must be accessed (defined by the orange cables in the engine compartment).
Replacing the Auxiliary Battery
12V auxiliary batteries have a useful lifespan of 3 to 5 years. However, battery longevity is affected by:
- Battery quality - not all auxiliary batteries are created equal.
- Driving habits (short trips vs highway driving).
- Climate and environmental conditions (heat accelerates battery degradation).
- Battery and vehicle maintenance.
Auxiliary Battery Maintenance
Here are the main points to consider for maintaining and extending the life cycle of your auxiliary battery:
- Drive or charge your vehicle regularly. The auxiliary battery is charged automatically when the high voltage system is powered up by driving or charging your vehicle.
- Consider using a maintenance charger or backup charger to keep the auxiliary battery charged if your vehicle will be left inactive for an extended period.
- Have your auxiliary battery’s State of Health (SoH) checked regularly with a digital battery analyser suitable for testing AGM & EFB type batteries.
Can I Start an Electric Vehicle With a 12-Volt Battery?
The answer may surprise you, but yes! As with vehicles with internal combustion engines, it may be possible to jump start your electric vehicle and drive away in peace. Here are a few tips:
- Don’t try to start your electric vehicle if you don’t know exactly what you’re doing. It’s best to contact a professional to avoid damage to the vehicle.
- An emergency start is always performed when the vehicle is not recharging.
- Please refer to your vehicle owner’s manual, as starter terminals may already be available on your vehicle.
- Never approach high-voltage orange cables. Do not touch or disconnect them.
- The use of an emergency starting device is highly recommended, as it features safety systems in the event of reversed polarity and can prevent a major disaster for the vehicle electronics.
- Verify the battery and charging system as soon as possible. Your local Nexdrive repair centre can help, and it can usually be done quickly.