Can I charge my i3 always on DC up to 80%?

[frooby]

Hello, I have just gotten my BMW i3 2016 model and I have been wondering what my best strategy is to charging it. I have been reading that DC charging is bad for the battery's health and so is charging it to 100%. Therefore, is it "ok" to always charge my car with DC if it's just up to 80%? If not, how often can I charge with DC?

 

[JohnKelly]

Do not worry about managing your charging. The car does it for you. It has a buffer at the top and will not let you charge to a true 100%. Just plug it in and leave it. DC fast charging every day for years might cause some degradation, but it is not worth worrying about in my opinion. The advice you have received is for Teslas with giant batteries and a different battery management system, not i3s. It is kind to others who are waiting to charge to vacate a DC station if you have reached the point where the charge rate is slowing down.. about 80-85%... otherwise, charge on!

 

[eNate]

The i3 is the only EV I'm aware of that doesn't offer ways to limit charge cutoff or warm against excess DCFC. I used to say "BMW is the only..." but that's changed with the i4 and iX offering watts to cut off and modify charging.

The top buffer is in the 5% to 7% range, meaning 100% indicated is still 93-95% full. This buffer is not uncommon. Other EVs offer buffers of various sizes as protection. Buffers have been shrinking as battery management systems become more advanced in newer cars.

With and battery the enemy is heat. i3 batteries aren't anything special. They're plate cooled but still get hot during charging, and DCFC crates in more heat than charging at a lower rate. There's no getting around that.

I mention all that only to finish with this: BMW didn't reinvent the battery for the i3 — it uses what everybody else uses. The BMS is old tech. I have no reason to not subscribe to industry best practices and limit DCFC and try to maintain my state of charge in the 20 to 80 range.

If I need to run to zero (also buffer protected), I will. If I need to charge to 100, I will. If I need to DC charge to 100, I will. And if I "accidentally" charge past 80 I don't sweat it. The BMS will do what it can to manage temps and limit charge.

But 2014 BMW didn't know something that 2021 BMW and other EV and battery manufacturers do not. In fact, maybe 2021 BMW learned something.