Comment by tantony | Hacker News Reader

Comment by tantony | Hacker News Reader

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I have owned a Model 3 in Iowa while living in an apartment with no garage. This was at the beginning of the Covid lockdown where it stayed unused for extended periods of time. The battery was cold-soaked in temps below 20F. Whenever I drove the car, I had almost zero regen-braking, reduced acceleration and the range was decreased by about 30%. For short commutes, that would persist throughout. But whenever I went on longer trips, a one hour drive would get it back to its original performance. The range would stay a bit lower due to higher energy use (~330 Wh/mi instead of 240 Wh/mi in the summer). The navigation would account for this when planning trips and also pre-condition the batteries prior to going to superchargers. On average it added maybe one extra charging stop during road-trips.

> almost zero regen-braking

This is interesting. I wonder if large capacitors could alleviate this: somewhere to quickly dump the regen energy, and charge the battery with it at some slow rate equivalent to the long-term average regen load. Not only would it help in cold situations where the battery can't be charged quickly, but also situations where the battery would be healthier if not charged quickly, which is always.

While not giving any energy back, Teslas can now detect when regen breaking is limited, and blend in the regular brakes for you, so that you don't have to change your driving style. It has only come out in the past couple of weeks, but I cannot tell the difference when regen is supposedly limited after enabling the feature. Before it was a little dangerous to have to modify your driving style and watch out for how much regen your car uses compared to its normal amount, since after a week of driving an EV in the summer you don't ever really touch the break pedal.

> almost zero regen-braking

Are you sure this is related to the cold, and not just that the batteries were fully charged so that regen had nowhere to put the energy?

[Edited to add]: I say this because I see this in all types of weather: I live on the top of a hill, and if the car is fully charge there will be no regenerative braking when heading down the hill.

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