• The battery in the pre-facelift Tesla Model S can be upgraded to a larger capacity.
• One owner swapped a 100 kWh pack in his 10-year-old EV that had a 70 kWh battery originally.

A used Tesla Model S can be a bargain if you’re willing to live with the fact that its high-voltage battery may be on its last legs. First-generation models can be had for around $10,000, which is a great value for a roomy and comfortable EV, but if the battery goes, a refurbished one from Tesla will set you back roughly $20,000. 

But there’s a solution that’s likely to be cheaper, and more importantly, could make an old Model S better than when it was new. In short, the battery pack can be upgraded to one with a higher capacity, which will, in turn, lead to more driving range.

This can be done on cars built until 2021, when Tesla discontinued what it called the Rapid Mate System, and it’s a rather straightforward job, if you know what you’re doing. That’s what Alex from Out of Spec Renew did with his 2015 Tesla Model S 70D.

The car had over 470,000 miles on the clock, and the battery pack was changed at around 250,000 miles, but it was the same 70 kilowatt-hour model that was available when the car was new. Now, though, Alex sourced a 100 kWh pack from a newer car that was wrecked, and decided to swap it into his 10-year-old EV.

A car lift is indispensable, and some small bits and bobs, such as a replacement high-voltage connector ring, are needed. A good understanding of how Teslas work is also important, as Alex found out after installing the new battery.

With the larger pack installed, the car threw a bunch of error messages. Moreover, one of the software update procedures failed at one point, which could be a bit unnerving for someone who’s not as well-versed as Alex.

One of the issues was a version mismatch between the battery pack and the car. But even after another reinstall, there were still several errors popping up on the display, so the owner let the car sit overnight, and the next day, he discovered that the issue was actually caused by a firmware misalignment. That was fixed by tricking the car into thinking it was a non-Performance model, and then, another software reinstall later, everything was all good.

The owner said he was “hoping to go double the distance” with the new pack, but stopped short of giving an actual figure. A comparison between the old 70 kWh pack and the new one will come soon in a new video, he said.

In any case, the larger battery is sure to improve the road-tripping abilities of this old Model S, which has nearly half a million miles on the clock and still works fine. When new, the 2015 Tesla Model S 70D had an EPA-rated range of 240 miles. By contrast, the 2019 Model S 100D was rated for 335 miles. That’s a big difference, and in this particular case, it could be even bigger, seeing how the car’s old pack had roughly 250,000 miles on it, so it could have been quite degraded. This inevitably leads to some range loss, which goes on top of the range loss caused by the pack’s age.

Meanwhile, the battery that was swapped in was made in 2022, so it’s just three years old. This means degradation is minimal, so the real-world range of this aging Model S could be over 300 miles. 

That’s impressive for a 10-year-old car, but what’s even more impressive is that this sort of thing is possible to begin with. Earlier this month, we wrote about Nissan Leaf owners swapping in larger batteries for their old EVs, and now we find out that the same can be done on the venerable Tesla Model S.