New battery research

New battery research

I’m intrigued by an article on Electrek today about a new Tesla battery design.
What I found particularly interesting is a graph, showing what I assume is the current battery used, having much better longevity when charged to 60% instead of 80-90%. Am I reading this right? Should I charge between 40-60% if I can?

derotam | 8 september 2019

From a technical perfection standpoint, yes 60/70% is better for the battery. But in practicality it doesn't matter if you go to 80/90%.

jordanrichard | 8 september 2019

I haven’t seen the article, but what new design. Tesla only uses 2 batteries, the 18650’s in the S and X and the 2170’s in the 3.

As for what charge level to go to, I will chime in with my experience over the past 5 1/2 years of owning my MS85. I routinely charge to 80% in the warner months and 90% in the colder months. I have 165,000 miles and have only loss 5% of range. The problem with only charging to 60% routinely is over time the algorithms for calculating available range start to get wonky because all it has to go by is your usage up to 60%. In other words, if you only charge to 60%, running it down to say 40% before charging back to 60%, the algorithms are only looking at 20% of how you drive. You need to think of your battery as a rubber band. If you only stretch it to “x” amount, as time goes by you forget just how far it can be stretched.

Lastly, if you only charge to 60% and you have an unexpected trip that you need to make, sitting at 60 or less %, may not be ideal.

kevin_rf | 8 september 2019

Unexpected trips are why I keep it at 70% in the summer, 80% in the winter. That said, when they do crop up, more often than one would think, no shame in stopping at an SC for 5 minutes to get you enough range to roll home. I would rather do that than charging to 90% each night.

HairyPiano | 8 september 2019

Article is here.

It’s entirely possible I misunderstand the chart but it appears they are benchmarking the new design vs the current battery. The chart seems to suggest a lot better longevity charging to 60. What am I missing?

vishious911 | 8 september 2019

The key IMO is #Equivalent full cycles.

If someone charges weekly (25 - 75%) -- this is ~150 miles per week, translating to ~8K miles a year. And this 25-75% utilization seems to retain 90% battery after 1000 cycles. 1000 such cycles imply a ~20 years of battery ownership. Most people _might_ replace their cars before 10 years.

But IMO, you are reading it correctly. Just have to _read_ the X-axis (full cycles) differently.

gmr6415 | 9 september 2019

@HairyPiano, I believe you are correct in that they are talking about a new battery design. Tesla recently patented a new battery using a new electrolyte composition.

Feb. 1st 2019

Tesla patents new battery cell for faster charge, better longevity, and lower cost

"Two-additive electrolyte systems that enhance performance and lifetime of Li-ion batteries, while reducing costs from other systems that rely on more additives. This disclosure also discloses effective positive electrodes and negative electrodes that work with the disclosed two-additive electrolyte systems to provide further systematic enhancements.”

jjgunn | 9 september 2019

@jordanrichard -- thx for the experience w/18650's. I have 36,000 miles on mine & been charging from 20% - 90%

It's my understanding the chemical composition of the 2170's are different. However, I'm wondering if the same rules apply.