protonic
Posts: 23
Joined: Mon Aug 31, 2020 7:52 pm

What does your "miles to empty" show when full?

Wed Sep 09, 2020 3:51 pm

I just bought a 2017 REX model a couple of weeks ago. My range will show 141 miles when full (comfort mode). I'm surprised it is much more than the 114 advertised. I realize this is based on driving habits, so I'm curious what everyone else shows for range after a "fill up". I don't drive like a grandma so I'm curious why the range is longer. I would've expected it to be shorter than advertised based on my driving style. Do you find that the estimated miles is a close estimate to actual miles driven?

I'm guessing hard acceleration reduces the range, but what other things are factors? My daily routine consists of a 5 minute drive to the highway, another 15 minutes on the highway (all at speed limit during this pandemic), then another 5 min to my building. I would think this is a typical commute. I have zero knowledge of how these electric cars work with respect to "MPG's". Does 30 minutes at 30 miles per hour drain the same amount of battery as 30 minutes at 60 mph? Does 15 miles at 30 mph drain the same as 15 miles at 60 mph?

Also, just to avoid making another post, do you need to go into "park" before shutting off the i3 or can you just push the "off" button? I'm lazy. LOL.

alohart
Posts: 2401
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: What does your "miles to empty" show when full?

Wed Sep 09, 2020 4:24 pm

It's even worse than that. The EPA range rating for the 94 Ah i3 REx is only 97 miles. 114 miles is for the lighter BEV that can use 6% more of its battery capacity than the REx before the REx engine starts.

The EPA range rating for 94 Ah i3's has always seemed low. The 72 mile EPA range rating for a 60 Ah i3 REx seems about right. The usable 94 Ah battery pack capacity is ~50% greater than that of the 60 Ah battery pack yet the EPA range rating is only ~35% greater. A slightly greater weight might be a small part of the explanation. So I think that the range that many 94 Ah i3 owners experience typically exceeds the EPA rating.

Aerodynamic drag is a significant force that reduces range, so range would be significantly less at 60 mph vs. 30 mph. Put another way, the battery pack's charge level would decrease considerably faster at 60 mph vs. 30 mph.

Rapid acceleration doesn't increase EV energy consumption as much as it does with an internal combustion engine. The additional electrical current required during rapid acceleration would result in an increase in waste heat because electrical resistance increases with current. However, it does increase the rear tire wear rate considerably.

If you're really lazy, park the car, pull up the emergency brake, exit the car, and lock the doors. That will automatically shut off an i3 and will shift to park (P).
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

protonic
Posts: 23
Joined: Mon Aug 31, 2020 7:52 pm

Re: What does your "miles to empty" show when full?

Wed Sep 09, 2020 4:34 pm

Wow, then I'm showing a 40% increase on my estimated miles to empty. I'll have to set my trip meter and see if I'm getting anything near that. I'm guessing it's not that accurate. I would assume the EPA estimates are almost unrealistic best-case scenarios.

alohart
Posts: 2401
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: What does your "miles to empty" show when full?

Wed Sep 09, 2020 5:19 pm

protonic wrote:
Wed Sep 09, 2020 4:34 pm
I would assume the EPA estimates are almost unrealistic best-case scenarios.
Not really. Even having lost ~20% of the new range of our 2014 BEV, our i3 consistently exceeds its 81-mile EPA range. When new, the predicted and actual range was ~105 miles, but that's driving a 100-mile loop without climate control, mostly flat but with one 1000 foot ascent and descent, at speeds mostly at 40 mph with less than 10 miles at 65 mph, at temperatures 75º F - 85º F, and with tires inflated 10 psi over the recommended pressure (lower rolling resistance and probability of pothole damage to the wheels). The average lifetime energy consumption rate reported by the BMW Connected app is 5.2 mi/kWh which is above average due to our ideal driving conditions.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

Pahaska
Posts: 77
Joined: Thu Jul 30, 2020 11:49 am

Re: What does your "miles to empty" show when full?

Wed Sep 09, 2020 9:24 pm

In my 2018 Rex, I get fully-charged readings around 140 most of the time. I have had several readings in the low 150s and a high of 155. It seems that after every charge, I get something different, although my daily driving is pretty consistent. The Rex mileage is a lot more constant and has been indicating 70 after a couple of test runs of a few miles since I coded it to allow maintaining the charge.

Now that our outdoor peak temperatures have dropped from over 100, I have been getting a lot better range.

Total mileage on the car is about 24,500 miles.

jadnashuanh
Posts: 5196
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: What does your "miles to empty" show when full?

Thu Sep 10, 2020 10:40 am

Probably your worst situation is lots of short trips where the car is parked in the sun, and you have the a/c set to a generally comfortable range. Well, on the REx, in the cold, heating is all via resistance heat, which is a lot less efficient than the cooling or heat pump on the BEV. It takes a lot of energy to cool the interior of the i3 with the large front windscreen. If you live in an area where they allow tinting the front windows, you might consider something like 3M's crystalline tint...even in the lightest tint, it blocks a significant amount of IR and UV light with the 200-layers of coatings on it. Then, running fast and not anticipating stops and using regeneration while actually using the friction brakes often messes up range. Not holding a steady speed, where you're constantly speeding up and slowing down (regen is never 100%) messes things up as does climbing a grade. Recently, I sat in a long line to get a COVID test (luckily, came out negative) and my efficiency for that trip was like 1-mile/kw...pretty dismal, but it was hot out, and was essentially not moving for most of the trip.

So, given the rolling average, some little things can combine to show either really good or really bad efficiency
Jim DeBruycker
2014 i3 BEV, 2021 X5 45e
(The i3 will be sold soon, <17K-miles, interested?)

protonic
Posts: 23
Joined: Mon Aug 31, 2020 7:52 pm

Re: What does your "miles to empty" show when full?

Fri Sep 11, 2020 1:52 am

Thanks for the replies!

How much does extra passengers effect your range? My other vehicle is in the shop and I'm going on a trip with the whole family this weekend in the i3 for the first time. Total weight would be about 500 lbs (me, wife and 2 small kids).

The trip is 80 miles so it's close to the 97 mile range. It also has a little elevation, starting at about 200 ft above sea level, climbing to 1600 ft half way there, and ending at sea level.

You think this can be done on battery alone? There would be no additional luggage (wouldn't fit anyway, lol).

jadnashuanh
Posts: 5196
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: What does your "miles to empty" show when full?

Fri Sep 11, 2020 4:14 pm

Once the vehicle is up to speed on the level, extra weight isn't a huge hit on efficiency, but climbing a grade, that weight becomes a factor. Going down, OTOH, you'll have more inertia, and be able to regenerate a little stronger with more weight in the vehicle. Your biggest potential range hit will be your speed, and how much stop and go you need to do during the trip. More people in the vehicle can also mean the a/c may need to work harder. If you want to maximize your range, consider slowing down a little while climbing the grade. Using one of the ECO modes, depending on the climatic conditions, should help your range, too. BMW says that running with the windows open above 25-mph uses more energy because of the drag versus using the a/c, so keep that in mind.
Jim DeBruycker
2014 i3 BEV, 2021 X5 45e
(The i3 will be sold soon, <17K-miles, interested?)

protonic
Posts: 23
Joined: Mon Aug 31, 2020 7:52 pm

Re: What does your "miles to empty" show when full?

Fri Sep 11, 2020 6:16 pm

Cool, thanks! Going to be leaving in an hour or so...

richs
Posts: 64
Joined: Sat Apr 04, 2020 5:09 am

Re: What does your "miles to empty" show when full?

Sun Sep 13, 2020 10:44 am

protonic wrote:
Wed Sep 09, 2020 3:51 pm
I just bought a 2017 REX model a couple of weeks ago. My range will show 141 miles when full (comfort mode). I'm surprised it is much more than the 114 advertised. I realize this is based on driving habits, so I'm curious what everyone else shows for range after a "fill up".
Wow. I have a 2017 REx (22k miles) and have never seen anything close to 141 miles of GOM range when battery full in comfort mode. Maybe 120 at most, and 110-115 more usually. Of course, my situation is probably different from yours. I have something of a worst-case heat scenario for an EV. I live in Texas, where it's routinely hot AND humid, I drive at 75 MPH a lot to keep up with traffic, and I don't have home charging, so pre-cooling the car generally reduces range for me instead of increasing it.

I'm interested to see how my GOM range will change as we head into fall/winter, which will ease my need for A/C considerably. I should, theoretically at least, see higher GOM ranges in winter than I do in summer (opposite of people in cold climates).

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