True power consumption

I have an I3 REX in its 4th year with 42,000 miles of which 32,000 electric

The computer dash tell me that I get 3.8 miles to the Kwh. If i look at actual Kwh required to restore the range (increase in reported range/kwh) back to 100% I get 3.4 miles to the Kwh and if I look at actual miles travelled the consumption is some 2.9 miles to the Kwh.

Not quite the save over petrol that BMW are claiming and not yet 50% through the promised battery life.

That said, apart from the engine mount issue fixed FOC by BMW, the only service costs have been tyres. Brake pads are just 50% worn !

I am using the "occasional" use charger all the time. Not sure if the efficiency differs from the heavy duty charging system?

dorowe said:

The computer dash tell me that I get 3.8 miles to the Kwh. If i look at actual Kwh required to restore the range (increase in reported range/kwh) back to 100% I get 3.4 miles to the Kwh and if I look at actual miles travelled the consumption is some 2.9 miles to the Kwh.

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dorowe said:

I am using the "occasional" use charger all the time. Not sure if the efficiency differs from the heavy duty charging system?

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You don't specify your location in your profile, but from your spelling, you're likely either British (230 V Occasional Use Cable) or maybe Canadian (120 V Occasional Use Cable).

A U.S. government lab tested the i3 charging efficiency at different AC charging voltages and currents. The most efficient, 93.8%, was 240 V at 30.1 A which is essentially the maximum charge rate the i3 internal charger supports. This is about 3 times the maximum current of the 230 V Occasional Use Cable (the charger is in the car, not in the cable). The least efficient, 84.1%, was 120 V at 5.6 A which is about half of the maximum current of the 120 V Occasional Use Cable. So regardless of the charging voltage and current, more energy is consumed to charge than had been consumed. Your charging appears to be ~90% efficient which is the explanation between the difference of 3.8 mi/kWh while driving and 3.4 mi/kWh while charging.

I don't understand the difference between your 2.9 mi/kWh and the 3.8 mi/kWh consumption figures. The dash displays the total consumption including climate control, accessory usage, and driving. I don't know of a way to display the consumption of driving only which would be less than the total consumption, especially when using resistance rather than heat pump heating.

Interesting as I'm running a BMW 225xe with a 30k battery milage average and not 41k as per BMW says. The car has travel 20,000k and 14,000k of the 20,000k is on battery. I'm very happy with the battery milage.

I would have though your i3 would have had a lower use of your petrol engine. You must not have many battery chargers close to where you travel.

Correct on location guess. I am based in the UK.

I have carried out the range tests by measuring the KwH required to return the battery back to 100% charge

My miles per kwh calculation is based on the following:

1) Miles per kwh as reported in the BMW app
2) Kwh required to get back to 100%/ change in range - ie. range at 100% charge less range at discharge point
3) Kwh required to get back to 100%/actual miles travelled

No surprise 3) is by far the lowest

Petrol mileage reflects use of I3 on long distance runs. No range limitation as far as I am concerned apart from having to stop every hour for more fuel.

dorowe said:

Not quite the save over petrol that BMW are claiming and not yet 50% through the promised battery life.

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Petrol gave away you are British.

We Canadians don't use that term. It's still gasoline/gas or fuel for us.