Tesla designed the Cybercab’s battery pack with spare space so it can later use cheaper lithium iron phosphate (LFP) cells, battery engineer Robert Sumpf told Munro Live. The robotaxi now uses Tesla’s 4680 cells. Tesla also said the Cybercab line can build cars faster than it deploys them.

Tesla designed the battery pack in its Cybercab robotaxi so it can later switch to cheaper lithium iron phosphate (LFP) cells. A Tesla engineer said so on the YouTube channel Munro Live, InsideEVs reported. The pack has spare room next to and under its modules.

Robert Sumpf leads mechanical design for Tesla’s battery modules and packs.

“So, we protected this pack to go to an even lower energy dense chemistry as we scale and need to bring LFP into the platform,” he said.

For now, the Cybercab uses Tesla’s own 4680 cells with a nickel-based chemistry. LFP cells store less energy, so the same number of cells would cut range, but Tesla could fill the spare space with more of them.

LFP cells are cheaper, more stable and last more charging cycles, which matters for a car Tesla says is built to run 500,000 miles. LFP became the world’s most used EV battery chemistry last year.

Tesla vice president Lars Moravy said the extra room was also there because “we didn’t need as many batteries as we thought we did.” Each module is sealed on its own, so one that fails can be swapped, unlike in the Model Y’s glued pack.

Moravy also said the Cybercab factory line can build cars faster than Tesla can put them on the road.

“We don’t run every day because the line can run so fast, it’s currently outpacing our deployments,” he said, Tesla North reported.

Every Cybercab built so far goes into Tesla’s own fleet, and Tesla said last week that Cybercab rides would start in Dallas in November. In August, Nevada approved just 10 of the 5,000 robotaxis Tesla asked for in Las Vegas.

The Cybercab has no steering wheel or pedals. In September, US regulators opened an investigation into how Tesla certified the car.