regen braking power indication wrong?

I've noticed this as well, and have assumed what the car shows when that number goes negative is just a simple regen calculation based on motor speed, ignoring any energy being spent to make it spin faster (feathering the accelerator for a more gradual deceleration).

 

Yeah it's a mess. It rises to as high as 20 in the coasting zone, but then flips to -20 if it just barely goes into regen and then tends toward 0 the more you regen. My Fiat 500e has a much better display that simply displays instantaneous power draw which goes to 0 when coasting and negative in regen

 

I’ve wondered about this as well.
In fact; I was wondering if there was brake blending going on, thus wasting energy, if you go too deep into the regen zone…

 

It's counter-intuitive, but the smaller the negative number, the greater the amount of energy you are recuperating.

• When the number is positive, it's showing you how many miles you can travel for every 1kWh of energy you're using.
• When the number is negative, it's showing you the distance (in miles) it would take you to regain 1kWh of energy.

So the shorter the distance it takes to regain 1kWh of energy, the more energy you are recuperating.

• At maximum recuperation, it would take just 0.8 miles to regain 1kWh of energy.
• If you're barely recuperating, it would take 20 miles (or more) to regain 1kWh of energy.

 

That’s why distance-per-unit (mpg, mi/KWh) isn’t as friendly as unit-per-distance (l/100 km, kWh/100 km).

 

The regen display is correct.
The Mini is set to regenerate at a constant declaration rate. While the power will vary with speed, the energy per distance at a constant deceleration does not.
If you are over around 50mph, the regen power is too high for the battery to accept, so you get less energy recuperated. You also slow down at a lesser rate, no wasted energy. If you have a very high charge, the car will simulate regen braking with the real brakes. That is wasted energy. I haven't worked out how to turn that off.

 

Anything other than Wh/mi (or Wh/km) is fine with me!

 

I did some checking today and that display doesn't seem to be what it seems it should be. When my SE was in neutral position it showed 20 mi/kWh. This was true regardless of the speed, and even when I shifted into neutral gear it showed 20 mi/kWh. As you accelerate the value drops quickly from 20 mi/kWh to under 2 mi/kWh, but then doesn't really go much below that even when you floor it. Going into regen the 20 mi/kWh immediately goes to -20 mi/kWh and then drops down to about -1.3 mi/kWh at maximum regen. When the SE stops moving the number changes to no value ("--").

I did find if you switch to kWh/100 km units it makes a lot more sense, with near 0 being the value at neutral and the number getting more extremely negative as the regen braking gets stronger. I'm not sure if the scale is something like a logarithmic scale, or if it's designed around kWh/100 km and so seeing it as mi/kWh is an inverted value.

 

You should be seeing -0.8mi/kWh maximum regen. This is only below about 50mph, owing to charging power limit.
If you are in a frigid wasteland, then the max speed for maximum regen will drop, but you should still see -0.8 at some speed if the battery temp isn't really extreme.

 

That's exactly what I see when set to mi/kWh.

 

Did you mean kWh/100 km? Otherwise, I am totally confused.

 

Assuming motion remains constant, say going down a grade, it would take just 4/5 of a mile to regenerate 1 kWh. It is confusing to think of it that way. Yes, the maximum regen I normally see using the less-arcane SI-derived unit is -77 kWh/100 km.

 

I see -0.8 mi/kWh max regen when I'm set to mi/kWh units.

 

In post 10, you said -1.3mi/kWh

 

So I did, I wonder what that's about. I know I see -0.8 mi/kWh pop up, so I'll have to do more observations.

 

Do you ever use the low regen setting? That could explain the higher value.

 

I just checked and it does peak at -0.8 mi/kWh, but you have to be going fast enough for the regen efficiency to get to that value. The higher value I initially said I received must have been at a lower initial speed with the SE coming to a stop before reaching maximum regen value.

(I almost never use low regen, for what it's worth.)

-0.8 mi/kWh is around -77.7 kWh/100 km, you can also see the inverse relationship between various mi/kWh and kWh/100 km values at this converter: Miles per Kilowatt-Hour to Kilowatt-Hours per 100 Kilometers Converter (Mi/kWh to KWh/100km).
if you could run at full-regen for 100 km you could easily completely recharge the SE! Would towing the SE (foot off the accelerator) work for regen?

 

No
No
Yes?