Highway efficiency?

[Tomasz]

So I have my i3 for a little over a week now and I'm using it to commute, which is a 40% of rural road (driven at 60mph) and 60% of highway (cruise control set at 70mph) with very little city driving on both ends (less than a mile total). My over all efficiency shown by trip computer is 2.9 miles/kWh.

I see people mentioning that they can drive all day at 70mph on Rex, Tom just did his trip where he posts overall stats showing 4.3 miles/kWh (and claims he was driving 70mph). I can sustain 65 at most, 62 seems to be my sweet spot. Also full tank of gas lasts only about 50 miles.

So far winter in Iowa wasn't particularly bad, temperatures stay around freezing point. I was driving in Ecopro mode with climate control temp set to 68F (how I like it, not to save electricity). My tires are set to 36psi front and 42psi back (according to TPMS).

Heck, I drove my Leaf the same road yesterday and got 3.2 miles/kWh (according to it's meter)

So what gives? What am I doing wrong that my i3 is so inefficient?

 

[i3atl]

So I have my i3 for a little over a week now and I'm using it to commute, which is a 40% of rural road (driven at 60mph) and 60% of highway (cruise control set at 70mph) with very little city driving on both ends (less than a mile total). My over all efficiency shown by trip computer is 2.9 miles/kWh.

I see people mentioning that they can drive all day at 70mph on Rex, Tom just did his trip where he posts overall stats showing 4.3 miles/kWh (and claims he was driving 70mph). I can sustain 65 at most, 62 seems to be my sweet spot. Also full tank of gas lasts only about 50 miles.

So far winter in Iowa wasn't particularly bad, temperatures stay around freezing point. I was driving in Ecopro mode with climate control temp set to 68F (how I like it, not to save electricity). My tires are set to 36psi front and 42psi back (according to TPMS).

Heck, I drove my Leaf the same road yesterday and got 3.2 miles/kWh (according to it's meter)

So what gives? What am I doing wrong that my i3 is so inefficient?

Partially the cold weather, but that still doesn't make sense. I just did a trip with the temp at 35F, climate set to 70, and after 77 miles @ 75mph the average was 2.9mi/kWh. This was with lots of hills, and in a heavily loaded i3 REx.

I've done several 60+ mile highway stretches at 70mph in a REx, including continuous hills, without any speed reductions. You should be able to sustain more than 62-65 unless there's significant elevation change involved.

Tire pressures on this REx were 38 all around, but I don't think your pressures are an issue.

 

[websterize]

Average speed, average wind speed, elevation change, average air temperature — there are so many additional variables. And only a week's worth of data. In other words, one size doesn't fit all.

 

[Sparky]

You may find the excellent speed control can drive more efficiently than you can. I use it as soon as I start driving.

 

[Tomasz]

I am lucky enough that I commute against traffic (from bigger city to smaller) so both of my morning and afternoon drives are on virtually empty roads. I hit cruise control about 100 yards from home and turn it off about 1 mile from work, return trip in reverse order. Average speed for my commute is between 59 and 60mph (I reset trip computer every time I leave the house, numbers are very repeatable)

I understand temperatures, wind, elevation changes. I get all that very well after driving the Leaf for over a year. But all that does not explain the fact that Leaf got 3.2 (vs. 2.9) on the same road, during the same weather and with the same load.

 

[i3MK]

I understand temperatures, wind, elevation changes. I get all that very well after driving the Leaf for over a year. But all that does not explain the fact that Leaf got 3.2 (vs. 2.9) on the same road, during the same weather and with the same load.

I hope BMW are taking note. There's no way a premium "luxury" electric car should be technically worse off than the mass market value end - which is what the Leaf represents in EV's.

 

[WoodlandHills]

How accurate are the respective meters and do they have their readings modified by an algorithm? If so they may both be just another Guess-O-Meter. Have you tried doing your own calculations to check them, or is that even possible without special equipment?

 

[mindmachine]

I am lucky enough that I commute against traffic (from bigger city to smaller) so both of my morning and afternoon drives are on virtually empty roads. I hit cruise control about 100 yards from home and turn it off about 1 mile from work, return trip in reverse order. Average speed for my commute is between 59 and 60mph (I reset trip computer every time I leave the house, numbers are very repeatable)

I understand temperatures, wind, elevation changes. I get all that very well after driving the Leaf for over a year. But all that does not explain the fact that Leaf got 3.2 (vs. 2.9) on the same road, during the same weather and with the same load.

You should be doing better then that at those speeds, at least based on my experience. I drive however on state routes and at speeds more like 50 to 60 with slowing down and speeding up with the traffic and in temperatures of 25 F to 40 F lately and am still getting 3.6 to 4.3 miles per kwh and I have a Rex with the extra weight. I would see what happens over a little longer time, but contact my dealer too. My lifetime average over 4 months (Sept to Dec this year) is 4.3 miles/kwh. Have you tried the ecopro + analyzer in the nav system.

 

[Tomasz]

How accurate are the respective meters and do they have their readings modified by an algorithm? If so they may both be just another Guess-O-Meter. Have you tried doing your own calculations to check them, or is that even possible without special equipment?

It is partially possible to test by measuring off the wall power used and drive with climate control set to off to make the results more comparable. But I'm not splitting hair here, I'm talking about usage way above what it should use. E.g. EPA lists Leaf as using 33kWh to get 100 miles, that is about 3.03 miles/kWh and that number is slightly below what I'm getting in my Leaf. On the other hand same EPA lists i3 as using only 30kWh per 100 miles on highway which should result in about 3.3 miles/kWh, yet my i3 is getting only 2.9 (and that is also confirmed by the range - my life time max. range on battery is 66.3 miles and average is about 60). And we have temps around freezing point right now. Can't wait to see when they drop to more typical this time of the year single digits.

 

[mindmachine]

How accurate are the respective meters and do they have their readings modified by an algorithm? If so they may both be just another Guess-O-Meter. Have you tried doing your own calculations to check them, or is that even possible without special equipment?

What other meters are you talking about, I don't see any reason why the miles/kwh would be altered by an algorithm. I mean it is what it is miles/kwh?

 

[I33t]

How accurate are the respective meters and do they have their readings modified by an algorithm? If so they may both be just another Guess-O-Meter. Have you tried doing your own calculations to check them, or is that even possible without special equipment?

What other meters are you talking about, I don't see any reason why the miles/kwh would be altered by an algorithm. I mean it is what it is miles/kwh?

My guess is that the best way to independently check would be to measure the power consumed at the plug and work out the miles per kWh from there. That would eliminate the guessometer etc and would be directly comparable between vehicles.

 

[jadnashuanh]

You put more through the EVSE than gets to the batteries, so while if everyone did that, it would be apples to apples, but it is not based on the car's indication verses the power it takes to recharge, which will always be more. It's worse if you are using level 1 verses level 2. I have not seen a comparison on the efficiency when using a DC fast charge, which has the potential of being more efficient IF you could measure the output of the DC fast charge verses what goes into it, since then the power conversion is shifted from the car back to the DC fast charger's power supply.