EPA Range, MPGe and Battery Capacity

[Roy2001]

I am surprised that no one questioned the EPA range and MPGe numbers.

The math is pretty straight forward, MPGe number is the range that EV can drive with 33.7kWh. So, if an EV can drive 2 miles per kWh, MPGe is 67.4 miles.

So, SR Lightning has 98kWh usable capacity, with 68 MPGe, you can get 2 miles per kWh, so 98 kWh battery could not privde more than 200 miles range. This is true to all Lightning models.

If 230 miles range for 98kWh battery is real, the MPGe would be 79 miles, which could not be true.

How can Ford rate it as 230/320 miles range? Is there any magic?

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[vandy1981]

It's not magic. MPGe includes charging losses in the calculation. Here's an explanation I posted on another forum.

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This is how I understand this issue. Someone please correct me if they insight in how MPGe is calculated.

The EPA efficiency formula incorporates charging losses. They generally hover around 10-15%. So using 15%:

0.85*51kWh/100mi=43.35 kWh/100mi
320 mi/[43.35 kWh/100mi]=138.72 kWh which is pretty darn close to the advertised battery capacity of 131 kWh.

If you want to back-calculate to get the Lightning ER's charging efficiency:

131 kWh/320 mi=0.409 kWh/mi
.409 kWh/mi*100 mi=40.9 kWh
40.9 kWh/51 kWh=0.802

So only 80.2% of the total energy coming from the wall 240 volt outlet gets stored in the battery pack as potential energy. The rest is loss to heat in the AC-to-DC converters, the battery cells themselves, and the cooling system needed to maintain a healthy battery pack temperature.

Keep in mind that this is calculated from a full 0% to 100% charge. there's going to a less entropy (and more efficiency) if you maintain charges below 80 percent because filling up the top of the pack requires more energy.
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[LightningShow]

Yeah, this has been discussed. MPGe is designed to determine energy cost to operate the vehicle. Range and mi/kwh ratings are related to driving efficiency. They don’t line up unless you know what the assumptions for energy losses are.

 

[Roy2001]

Yeah, this has been discussed. MPGe is designed to determine energy cost to operate the vehicle. Range and mi/kwh ratings are related to driving efficiency. They don’t line up unless you know what the assumptions for energy losses are.

That is NOT true.

MPGe calculation is based on how many kWh Lightnings draw from wall, not how many saved in battery.

Let's see when people get their trucks.

 

[LightningShow]

That is NOT true.

MPGe calculation is based on how many kWh Lightnings draw from wall, not how many saved in battery.

Let's see when people get their trucks.

That's exactly what I said. You pay for the electricity that comes out of the wall...so MPGe is designed to tell you how much the electricity costs to drive the a given distance.

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