Electric car batteries should not, generally, be charged to 100%. Long-term, this reduces the battery’s longevity, and Tesla cars actually charge up to 90% by default.
But if you’re pressed for range, should you change this and charge up to 100%? Well, unless you absolutely must squeeze every bit of range out of your battery, the answer is still no.
It’s not just about battery degradation. In a recent Twitter exchange, Tesla CEO Elon Musk explained that regenerative braking does not kick in at full charge, meaning the car is less energy efficient.
A Tesla Model 3 owner asked Musk whether she should charge up to 100%, given her commute is a total of 160 miles, which leaves little wiggle room to do much else with the car without a recharge. Her Model 3 is the Standard Range Plus variety, which has 240 miles of range at full battery capacity, but this drops to about 216 miles at the default 90% charge setting.
Musk’s answer is that she should still charge to 90% or 95%, to reap the full benefit of regenerative braking.
It’s not a big deal. Charge to 90% to 95% & you’ll be fine. At 100% state of charge, regen braking doesn’t work, because the battery is full, so car is less energy efficient.
— Elon Musk (@elonmusk) April 16, 2019
Regenerative braking is the tech that turns braking energy into electricity, extending the car’s battery range. Its effectiveness varies by a number of factors, but there are reports of it extending a Tesla’s range by as much as 30%. So charging the battery to 95% might actually be almost as good, range-wise, as charging to 100%.
To know exactly how close the numbers get, one would have to know when, exactly, regenerative braking kicks in. I’ve pinged Musk for the answer and will update the article if I get it, but anecdotal evidence from Tesla forums suggests that it happens when the battery is anywhere from 84% to 94% capacity, so roughly in line with what Musk had said — but ambient temperature is also a factor, so your mileage (literally) may vary.
These types of tricks will likely become common knowledge as electric cars get more popular, but now they’re still exotic to many users who are used to filling the car up to the max. But electric battery-powered cars offer many advantages that ICE cars don’t — regenerative braking being one of them — and the sooner we learn to reap the full benefits, the better.