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Regen Braking - Charge Dependent?

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Recent M3 purchase.

I understand varieties, regen, etc are effected by weather.

Our weather has been 30-35 recently. I have noticed that even after the car sits for 8h, then warmed up for 10m that if the battery is above 55% I get limited regen braking messages. However if the battery is less then 55% I constantly get full regen braking.

Any ideas? Is that by intention or? Trying to figure this out as even if I turn the climate on for 30m when the battery is above 55% it doesn’t matter which leads me to think it’s my understanding of regen braking or software.
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Regen decreases when battery is cold, when battery is full, or both. Depending how cold the battery (and ambient temp) is, how much you need to heat the battery for proper regen. If no regen, you might need to heat it more... but reportedly it's not worth to waste energy doing that, unless you're going on a long trip. But I'm still learning all the details of EV ownership :).
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Yes, the amount of regen available is directly related to how full your battery is, and how cold it is (and potentially how cold the motors and inverters are - though I don't know that for certain). I'm sure someone at Tesla has an exact mapping of battery temp, SoC (State of Charge), etc... but for the rest of us, the colder it gets, or the fuller the battery is (or both), the less regen you have. Also, if you bought the single motor M3, you're starting off with about half the regen capacity of the dual motor.

I don't like giving advice on anything related to cold weather seeing as how we are having a 85-90 degree weekend here in Murrieta, CA. But my experiences (and it DOES drop into the low 20's here at night) tell me that preheating the car for the purposes of gaining more regen is not worth it. You'll use far more power than you save via regen. I only pre-heat or pre-cool for the occupants of the car. I'm going to mirror the advice I've heard others say on this forum, let the car worry about the battery temp.

Plus, it is important that you use your brakes occasionally anyhow. Keeping them clean and moving freely is vital given how little use they'll get compared to an ICE car.
Why does it have to used for anything? The power output could just be switched off.
Then there would be no resistance in the motor to slow you down. For instance, when they don't want to store the power on large electric/diesel trains they simply dump the power into a huge resistance heater and blow the heat out of the top of the train. :)
Why does it have to used for anything? The power output could just be switched off.
Why? Physics. The whole point of regenerative braking is to slow down. If a generator is running with no load, it's very easy to spin. Like a bike going downhill is easy to pedal. In order to make it harder to spin, the load on the generator has to be increased, like trying to pedal uphill. So no load, no slow. High load, high slow. Thus, in order to have a braking effect, there must be a load on the generator. In EVs, that load is the battery. In diesel electric trains the load is a giant bank of resistors that get very very hot. In either case, the energy generated must be absorbed by something, else there is little braking effect. If the battery cannot take a charge, or the resistors are too hot, then friction braking must be used, as there is no slowing effect otherwise. See Dynamic braking - Wikipedia
It seems to me that regen doesn't have to be limited in any situation. Regen doesn't provide that much juice anyway but I'd think Tesla could have had the regen power not charge the battery at all, if the battery was at a high state of charge.

This comment is totally not true. The reason why regen IS limited in low temperatures and/or state of charge above 80% is regenerative braking from the motors is a lot of KWs.

If you had the Scan My Tesla tool, you can see the regen power limit at anytime. When regen braking the power can be in the 100KW+ range. So if the battery is cold or full, the regen has to be limited just like how they limit charging speed.
I wish the car had a bank of resistors that could be used for resistive braking when the battery is cold. The resistors could heat the battery coolant to warm up the battery quicker while applying braking until it's ready for regen.