EV’s Second Battery

Here’s something that surprises people outside the industry. Almost every electric vehicle on sale today carries two batteries. The big one, typically 400 or 800 volts of lithium, drives the wheels. The small one is a low-voltage battery, usually 12 volts, and on most models it’s a lead-based AGM battery much like the one that sat in petrol cars for decades.

Why it’s still there

It’s not there out of habit. The low-voltage battery powers the contactor, the safety switch that connects and disconnects the high voltage pack. In a collision, that’s the component that isolates hundreds of volts from the passengers. It also runs the locks, lights, screens and safety systems, because those sit close to the people in the car, and powering them directly from the traction pack would require layer upon layer of extra protection. If the 12 volt battery dies, the car won’t start, even with a full traction battery.

Who owns the position

Most EV models on the road, including most from Ford, General Motors, Hyundai, Kia, Rivian and Volkswagen, use AGM lead batteries in that position. Being honest, the picture is shifting at the top: Tesla has moved many models to lithium low-voltage batteries, and BYD uses lithium in some of its models too. But across the market as a whole, the low-voltage position still belongs mostly to lead, and the companies that own it are the low-voltage specialists. Clarios, which says its batteries sit in one of every three cars on the road, has gone further and is investing in sodium-ion low-voltage batteries with Altris, a sign the 12 volt specialists intend to own whatever the position becomes next. Banner, GS Yuasa and Exide supply the same market in Europe and Asia.

The regulation agrees

The EU’s Batteries Regulation gives SLI batteries their own category, with a minimum of 85 per cent recycled lead content from 2031, the highest of the four materials covered by Article 8’s targets. You don’t write a dedicated target for a product you expect to disappear.

The 12 volt battery survived the death of the starter motor, which was its whole original job. What do you think the low-voltage position looks like in 2035: lead, lithium, sodium, or gone?