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You lose about 5% capacity in the first 45k miles, then it's essentially flat- 3% in 120k miles. It seems like keeping your charge level at 100% has some impac
by hwillis 9y ago
You lose about 5% capacity in the first 45k miles, then it's essentially flat- 3% in 120k miles. It seems like keeping your charge level at 100% has some impact on lifetime, but lower than 90% looks to have very limited returns. I'll be interested to see how the cycle graph evolves, but right now it looks like batteries will on average make it to 2500-3000 cycles, which is great.
There are a number of early outliers that had more significant capacity loss. They're all from the US- Europe & Asia have over 800 reports compared to 170 in the US, but the lowest reading there is 88% compared to 85% in the US. All with ~<35k miles, <4 years old, mostly 60 kWh models. I'm not quite ready to call fake, but the numbers from the US are definitely unlike other countries.
Those cars weren't driven nearly as hard as their counterparts in other countries. The only real explanation other than false reporting is heat, but unfortunately there is no indication of location besides one guy in Michigan. Keep that in mind when looking at all the graphs- the lowest data points are almost exclusively very strange outliers from the US that weren't driven particularly hard.
- ProfessorLayton 9y agoIIRC no high voltage car batteries are actually charged/discharged 0-100%, even if it reads so from the user's perspective. This is due to significantly increased wear on the batteries when fully charged/discharged, and why a cellphone battery only lasts a few years. The batteries need to be significantly over-provisioned to extend their lifespan. A Prius, for example, will keep the battery's SOC between 40-80%, and is one of the most reliable hybrids out there. The same is true for EVs, so charging it till it reads 100% does not mean the battery is at capacity. The same is true when it reads empty.
- mikeash 9y agoI don't think any lithium ion battery is ever truly used at 0-100%. True 100% would be just before it explodes, and true 0% would be just before it completely bricks. You get horrible degradation near those areas so they're always avoided. I'm sure consumer electronics push it farther than cars do, though.
- hwillis 9y agoThe "sticker" capacity on a Tesla is usually ~3% lower than the real capacity (the one in EPA filings), but the car lets you chose any charge level up to the sticker rating. That's the one I'm talking about- I just mean as relevant to an owner.