The Regen Instant Consumption (Negative mi/kWh)

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Ssbg58

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I swear I searched around and I couldn't find a proper explanation (F56).

What does the negative miles per kilowatt actually represent? I know it's regen, but I am confused by the units, specifically, it seems to me that least amount of regen is applied (not releasing accelerator pedal all the way) recoups more power (reading is usually closed to
-20mi/kWh) than a sudden abrupt regen (value closer to "-1mi/kWh").

If the unit was kWh/mi, negative values makes sense (can we switch that?). Ultimately, I am curios does it make a difference - smoother regen vs fast and strong regen. Thanks.
 
Just drive your SE the way you want and have fun! The BMW i3 could get 8+ mi/kWh and nobody cared. Now auto reviewers are fawning over 3 mi/kWh.

As for braking, the limit is really how much the motor (~135kW) can run in reverse before the rest is lost as entropy via tires/drag/brakes. So the real difference is how much one pedal driving you can actually do.
 
The search isn't always great. It took me a few tries to find my response in the regen braking power indication wrong? thread from last year:
MichaelC said:
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.
Click to expand...
 
That's why SI for vehicle fuel economy (etc) is so much better. It's quantity consumed per set distance, so for EVs it's kWh/100 km when drawing juice, and negative kWh/100 km when regenerating
 
SameGuy said:
That's why SI for vehicle fuel economy (etc) is so much better. It's quantity consumed per set distance, so for EVs it's kWh/100 km when drawing juice, and negative kWh/100 km when regenerating
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While I don't really disagree with your point, energy/distance isn't an SI convention, is it?
 
Should've said "SI-based.":cool: The common format in metric countries is "fuel consumption" (consumable per unit of distance) while in places that use US or imperial units it's the reciprocal "fuel economy" (distance per unit of consumable).
 
SameGuy said:
Should've said "SI-based.":cool:
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Quibbling only in fun, I'm not sure even that statement stands up. The SI unit for energy is the joule (J), not kilowatt-hour (kWh).

Hmm. 1 kWh = 3.6 MJ, or about the same as a kilogram of apples. So, our 32.64 (gross) kWh battery packs store about as much energy as 33 kg as apples, but weigh, what, about 5 times as much?
 
I believe 1 calorie = 0.0001163 kWh and an apple is somewhere from 50 to 150 calories depending on the size and density.

Let's say 100 calories per apple so the 32.64kWh gross battery pack would need about 2,800 apples (~500kg) before the anode/cathode/electrolyte and cell casing material. Now if you have discovered some super energy dense apple, I'd like to solve world food hunger.
 
teslarati97 said:
I believe 1 calorie = 0.0001163 kWh and an apple is somewhere from 50 to 150 calories depending on the size and density.

Let's say 100 calories per apple so the 32.64kWh gross battery pack would need about 2,800 apples (~500kg) before the anode/cathode/electrolyte and cell casing material. Now if you have discovered some super energy dense apple, I'd like to solve world food hunger.
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There are 239 kilocalories in a MJ. That's only 239 Calories. 239 x 32.64 = 7801 Calories. At 100 Calories per apple, that would be only 78 apples, not 2800.
 
Yes there are 238.85 kilocalories in a MJ (MW) and there are 859,850 calories in a MWh. Since I suck at maths...32.64kWh * 1MWh/1,000kWh * 859,850 kilocalories/1MWh * 1000 gramcalories / 1 kilocalorie = 28,065,504 gramcalories.

28,065,504 gramcalories dividend by 100 gramcalories per apple would take about 280,655 apples.
 
teslarati97 said:
Yes there are 238.85 kilocalories in a MJ (MW) and there are 859,850 calories in a MWh. Since I suck at maths...32.64kWh * 1MWh/1,000kWh * 859,850 kilocalories/1MWh * 1000 gramcalories / 1 kilocalorie = 28,065,504 gramcalories.

28,065,504 gramcalories dividend by 100 gramcalories per apple would take about 280,655 apples.
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You're right, I forgot the 3600 seconds per hour in my second post.

Still, it would seem that the point stands: the energy density of apples is much greater than that of our battery packs. (Of course, that's because we complete "burn" the apples, but only discharge/recharge batteries.)
 
Puppethead said:
"My car gets forty rods to the hogshead"

Click to expand...

As I’m reading all comments about BTU’s kWh jule(J)kcal Mwh &apples this is out of many people knolage without PhD or a little lower education as a high schoolers can’t do a simple math as 25 % of a $ 1 as you see shopping in grocery stories !!!
 
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