12V AUXILIARY LITHIUM BATTERIES

What Does the 12V Auxiliary Battery Do?

Separate from the main high voltage pack, the 12V auxiliary battery runs the everyday stuff: dashboard, infotainment, lights, windows, airbags, ABS. More importantly, it powers the relay that closes the contactors and connects the high voltage battery to the rest of the car.

That’s why a dead 12V battery is more serious in a hybrid or EV than in a normal car. It doesn’t just stop the engine turning over, it can leave a fully charged EV completely unable to move, because the high voltage system never gets the signal to switch on.

There’s no alternator charging this one either. A DC/DC converter steps the high voltage down to 12V and tops up the battery as you drive. Increasingly, manufacturers are also moving away from lead-acid (AGM) toward lithium-ion for this battery, mainly for the weight saving and longer cycle life.

Below you’ll find new, used and refurbished OEM 12V auxiliary batteries and individual modules for your make and model, tested for state of health before shipping and covered by warranty.

Signs of a Failing 12V Auxiliary Battery

• Car won’t enter “Ready” mode, or won’t start at all, even though the high voltage battery is full
• Battery or charging system warning light on the dash
• Interior lights dimming or flickering, sluggish infotainment
• Slower cranking than usual on hybrids that use the 12V system to start the engine
• Contactors not engaging, so the high voltage system can’t switch on

New, Used & Refurbished OEM Units & Modules

These batteries are available as complete units or as individual modules, in new, used and refurbished condition depending on what’s available for your vehicle. Every one is tested for capacity and health before it ships, and covered by a 12-month warranty.

Compatible Makes & Models

Filter by make below, or search directly by part number.

Testing, Warranty & Exchange Service

Each 12V auxiliary battery or module is tested for capacity and health before leaving our warehouse and comes with a 12-month warranty. On exchange parts, we hold a refundable deposit until we receive your old unit back.

Frequently Asked Questions

Can I jump-start a hybrid or EV using the 12V battery?

Yes, that’s the one to use, never the high voltage pack. Check your owner’s manual first though, since connection points vary by model.

What are the warning signs of a failing 12V battery?

Usually a battery or check-engine light, the car refusing to enter Ready mode, glitchy infotainment, or a no-start despite a fully charged main battery.

Why do some hybrids and EVs now use lithium-ion instead of lead-acid for the 12V battery?

Mainly weight and lifespan. Lithium-ion packs are lighter and hold up better under repeated cycling than the older AGM lead-acid batteries.