Charging (In)Efficiency

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Zim said:
50 MPG sounds great in theory, but those average figures, especially in the winter, are far from 50. A 20-25% hit isn't unheard of, we saw such a hit with the Malibu below 20F. If such a vehicle is a hybrid, expect a slightly larger hit with hybrid battery inefficiency. And an overall larger hit if one has a habit of pre-warming at idle before setting off.

Winters are tough on transportation.
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Remember, as @Carsten Haase pointed out, using the EPA's formula of a gallon of gas being equal to 33.7 kWh, the gasoline-equivalent of a fully charged MINI Cooper SE battery is only 0.88 gallons of gas. How many ICE cars can go 177.65 miles on 0.88 gallons of gas?
 
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Zim said:
And an overall larger hit if one has a habit of pre-warming at idle before setting off.

Winters are tough on transportation.
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It's brutal if you have a foot of snow on your vehicle parked outdoors in -35F weather. The vehicle literally has to idle for 30 minutes to clear off the entire vehicle. Lazy drivers rather get fined by the police because they can't clear the roof on their 3rd row SUV. Mileage can drop 50%+ during a snowstorm.
 
insightman said:
Remember, as @Carsten Haase pointed out, using the EPA's formula of a gallon of gas being equal to 33.7 kWh, the gasoline-equivalent of a fully charged MINI Cooper SE battery is only 0.88 gallons of gas. How many ICE cars can go 177.65 miles on 0.88 gallons of gas?
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If 40% is lost due to charging, then you have to compare to 1.4 gallons. So that's 127 mpg equivalent. I wish I could get that. I think average good-conditions range for this car is around 120 miles, not 178.

Anyway, the EPA formula is nonsense. The correct way to assess this is miles/$. At 60% charging efficiency, it costs me $6 to fill the battery at standard electric rates. That buys around 2 gallons of gasoline. There are plenty of cars that can go over 100 miles on 2 gallons of gasoline.
 
JZ99 said:
If 40% is lost due to charging, then you have to compare to 1.4 gallons. So that's 127 mpg equivalent. I wish I could get that. I think average good-conditions range for this car is around 120 miles, not 178.

Anyway, the EPA formula is nonsense. The correct way to assess this is miles/$. At 60% charging efficiency, it costs me $6 to fill the battery at standard electric rates. That buys around 2 gallons of gasoline. There are plenty of cars that can go over 100 miles on 2 gallons of gasoline.
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I'm getting ~85% charging efficiency with my L2 EVSE... If you are really getting 60% it sounds like something is wrong (or maybe the stock MINI charger just sucks?). My long term average in good conditions and more highway than city is 136mi. Not 178 but more than 120.

Miles/$ may be good for an individual but because the cost of gas/electricity and mpg is so variable it does not make any sense as a published figure. It costs me $3.20 to fully charge my SE which would buy 0.86 gallons of gas. Quite a bit different than you.
 
There must be more factors involved beyond the level 1 charging from the OP. Is it an older home (and older wires) with a detached garage far away from the main panel?
 
How are you all getting your charging efficiency? It is the reported kWh from the Mini Charging Sessions app vs what your EVSE shows as going into the Mini?
 
I just calculated the charging efficiency on a few trips (I looked at the longest charges in my history) and show 60-66% efficiency. Anyone want to loan me a L2 charger to do a comparison? :p

The house itself is old, but I ran all the wiring to the detached garage a couple years ago so it's all new wire back to the main panel. The previous owners upgraded to 200A service, and I installed a 60A subpanel in the garage. It's only about 30 feet between the main panel and the garage so I wouldn't think line loss would be that bad.
 
teslarati97 said:
There must be more factors involved beyond the level 1 charging from the OP. Is it an older home (and older wires) with a detached garage far away from the main panel?
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I'm measuring the kWh coming out of the wall, so the house wiring is irrelevant. It happens to be a modern house, anyway. The charging load is pulling voltage down from 123V to 121V at 10A. But Watts is Watts. Power Factor is 0.99.
 
chrunck said:
I just calculated the charging efficiency on a few trips (I looked at the longest charges in my history) and show 60-66% efficiency. Anyone want to loan me a L2 charger to do a comparison? :p

The house itself is old, but I ran all the wiring to the detached garage a couple years ago so it's all new wire back to the main panel. The previous owners upgraded to 200A service, and I installed a 60A subpanel in the garage. It's only about 30 feet between the main panel and the garage so I wouldn't think line loss would be that bad.
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Surely, someone with an L2 charger can post some data.
 
GvilleGuy said:
How are you all getting your charging efficiency? It is the reported kWh from the Mini Charging Sessions app vs what your EVSE shows as going into the Mini?
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It's mostly being indirectly calculated. Some are including the entire battery (usable + buffer) and others are calculating on the usable 28.9kWh such as AndysComputer.

chrunck said:
The house itself is old, but I ran all the wiring to the detached garage a couple years ago so it's all new wire back to the main panel. The previous owners upgraded to 200A service, and I installed a 60A subpanel in the garage. It's only about 30 feet between the main panel and the garage so I wouldn't think line loss would be that bad.
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The losses will be nominal if it's all new (copper) wire and a relatively short distance from the main panel. You could read up the 2017 BMW MiniE tests on bi-directional charge/discharge losses:
https://www.sciencedirect.com/science/article/pii/S0360544217303730#sec3
 
Carsten Haase said:
I'm getting ~85% charging efficiency with my L2 EVSE... If you are really getting 60% it sounds like something is wrong (or maybe the stock MINI charger just sucks?). My long term average in good conditions and more highway than city is 136mi. Not 178 but more than 120.

Miles/$ may be good for an individual but because the cost of gas/electricity and mpg is so variable it does not make any sense as a published figure. It costs me $3.20 to fully charge my SE which would buy 0.86 gallons of gas. Quite a bit different than you.
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Thanks, good to know.
 
chrunck said:
I used the formula AndysComputer used on page 2. Percent charged x 28.9kwh / kwh from the charging history.
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I still can't understand how this is being calculated. Maybe someone can illustrate with actual numbers? Here's my last (level 2) charge session (outdoors, temperature -3 ºF).

level2charge.webp
 
Puppethead said:
I still can't understand how this is being calculated. Maybe someone can illustrate with actual numbers? Here's my last (level 2) charge session (outdoors, temperature -3 ºF).

View attachment 14944
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Sure, you charged 14% of the battery (66% - 52%), and it used 4 kWh of juice. 14% of the total battery is 4.046 (0.14 x 28.9). The efficiency is 4.046 / 4 = 101% efficiency. Your house is magic!
 
Who was the person on here that received two different chargers with their MINI? I'd be curious to see how the other charger is performing.
 
Puppethead said:
I still can't understand how this is being calculated. Maybe someone can illustrate with actual numbers? Here's my last (level 2) charge session (outdoors, temperature -3 ºF).

View attachment 14944
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Hey, I'm in Twin Cities too (Victoria). How's your mileage in these sub-zero conditions? Yesterday, my wife got a whopping 2 miles/kWh (1.3 measured at the wall).
 
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