REX is underrated!

[agzand]

This week I did an 820 mile round trip in span of 1.5 days in my 2018 94ah i3 REX. On second day (480 miles) I was caught in California atmospheric river torrential rain on multiple occasions. I was able to complete the 405 mile return trip in 7hr 45min thanks to REX. I could even shave another half hour if I had forgone two 20%-85% fast charging sessions.

I also drive a VW iD4 and have done the same trip with VW, and I am not sure I could have done it in the same time despite much larger battery.

The REX worked surprisingly well, even climbing Tejon pass at 65-70 mph I lost maybe 10% battery charge. I don’t use my REX too often but recently had an oil change and did the fuel additive/injector cleaner thing that the dealership recommended. Not sure if it had something to do with it.

One thing that I noticed is that once conditions are not ideal (rain, cold etc.) REX miles somehow appear longer than battery miles. I think I got around 45 mpg on REX.

I think it is a shame that BMW abandoned this technology in favor of larger and larger batteries. I for one would be willing to buy another REX if BMW or someone else (Mazda maybe?) comes up with an up with a compelling model.

Two things that I would improve is slightly larger gas tank (3 usable gallons instead of 2) and using engine heat for cabin heating.

 

[iCJ]

I agree, if our second car was not an ICE I would have the Rex. Been a few times where I said to myself I should have bought the Rex, but on those longer trips not having the lane centering (auto steer) I end up saying the the i3 needs this before I consider the Rex.

On your trip did you use the adaptive cruise? Also did you use it in the heavy rain? I love the i3 adaptive cruise, and depending on how I set it find it very smooth. I don't use it in bad conditions only because other drivers are just bad so feel more comfortable when I am in full control.

Another question with the REX and how you use it, what is the battery buffer you like to keep on long trips or do you just kick it in at 75% and just roll on dead dino carcass juice from there on out?

 

[agzand]

Yes, I used adaptive cruise for the most part, particularly on day 1 with better weather. It reduces the stress on driver. I did not use it in heavy rain (you should not use adaptive cruise in heavy rain in general). It works very well for such a simple hardware. It did disengage on two occasions, so you need to be alert to take over quickly, because once it disengages the regen kicks in. Another quirk of i3 (regular not the i3s) is that it is sensitive to cross winds, so I had to be careful on two sections to keep the car between lanes.

I typically engaged the REX around 60-65% SOC, then disengaged once gas range was around 2-3 miles, it takes a minute or so for engine to shut off, so by that time gas range drops to 1 or 0 miles. I guess the gas tank has some buffer, so it shouldn't matter if gas range drops to zero. Once you are at 0 mile range it takes about 2.1 gallons before the pump clicks (I wish it could take 3 gallons). I know this route (Orange County to San Francisco Bay) pretty well in terms of charging stations, slopes etc., so I did all the calcs in my head, where to stop for charging, where start the REX etc. With REX you have a "get out of jail" card, so it is not as critical as a BEV.

I set the AC to 66-68 and put on a sweater, the rex was able to maintain battery level at 75 mph (outside temp around 50-55 F). I guess I had some tailwind on my way back which helped. Going up the Tejon pass at 65 mph (about 4000 ft elevation gain) I lost some SOC, I guess 8 to 10 percent.

Overall i3 is pretty good at maintaining efficiency at highway speeds. Most EVs lose more efficiency going from city to highway speeds.

 

[iCJ]

Hvac at 66f, I don’t think I’ve set mine below 72. I like things toasty, and on long drive to take jacket off.

Have you done a trip where you just did gas? I guess with elevation gain you probably need both if keeping 75 mph. Even in my previous supercharger car I would set cruise at 65 and chill in the right lane. Letting all the people fly by. Now with the electric car I get the stares, before nobody cared.

Surprisingly the i3 has seats that fit me perfectly. How are you finding it on long trips?

 

[agzand]

On longer uphills sections you will lose battery charge even when hold state of charge is enabled. As mentioned I lost about 10% SOC climbing about 4,000 ft at Tejon pass, and I was doing 65-70 mph only.

The i3 seats are comfortable for me, and the expansive driver space reduces fatigue, but the twitchy steering and short wheelbase are not very well suited to long drives. It is OK as long as it is not windy. At high winds you need too much steering correction to be a comfortable drive.

 

[tomsupernerd]

We did a road trip from MN to DE last fall with our 2016 i3 with REX. We used gas most of the way, keeping the battery over 25% for peace of mind. We also had the Wavian NATO Jerry can in the frunk, and used it mostly at the end of the day when we pulled into a campsite. Having to stop every 75 mins or so for fuel was not a problem, actually made me feel much better getting up and moving more often. I was a little worried when we started out, but wouldn't hesitate to do another road trip. We also found several free chargers along the way. The best one was Shenandoah Nat'l Park, getting a charge while we went for a nice long hike. Most unusual was a public library in some small town in Kentucky, with wi-fi so we could both work on our laptops while the car charged. Our average mpg was 42, with about 500 miles on electric with free chargers, and about 1000 miles on gas.

 

[agzand]

I agree that fueling up every hour or so is not that bad. It is still much faster than charging a long range EV. You can practically fuel up in the time that it takes to start a charging session.

The engine on 2017+ models is 38 hp (28 kW). Assuming 75% efficiency it can generate 21 kW electricity. If the car consume at 3.6 miles per kWh (0.286 kWh per mile), the engine should be able to maintain 75 mph.

If you are going uphill consumption could drop to 2.0 miles per kWh or even lower, so the engine can maintain 42 mph only, if you go faster the SOC will drop. But if you have hold sate of charge enabled and drive at reasonable speed, you should still be able to climb a sizable mountain pass (like 8000 ft or so). The engine becomes noisier than typical highway driving when you do this though.

 

[BLINGMW]

Wish I could take it out when autocrossing, but other than that, love my REX too! People ask me about public charging stations in our area and I'm like, dunno, never used one.

 

[PaulineJensen]

This week I did an 820 mile round trip in span of 1.5 days in my 2018 94ah i3 REX. On second day (480 miles) I was caught in California atmospheric river torrential rain on multiple occasions. I was able to complete the 405 mile return trip in 7hr 45min thanks to REX. I could even shave another half hour if I had forgone two 20%-85% fast charging sessions.

I also drive a VW iD4 and have done the same trip with VW, and I am not sure I could have done it in the same time despite much larger battery.

The REX worked surprisingly well, even climbing Tejon pass at 65-70 mph I lost maybe 10% battery charge. I don’t use my REX too often but recently had an oil change and how to get rid of moobs did the fuel additive/injector cleaner thing that the dealership recommended. Not sure if it had something to do with it.

One thing that I noticed is that once conditions are not ideal (rain, cold etc.) REX miles somehow appear longer than battery miles. I think I got around 45 mpg on REX.

I think it is a shame that BMW abandoned this technology in favor of larger and larger batteries. I for one would be willing to buy another REX if BMW or someone else (Mazda maybe?) comes up with an up with a compelling model.

Two things that I would improve is slightly larger gas tank (3 usable gallons instead of 2) and using engine heat for cabin heating.

Yeah REX works well mostly in Emergency situations. I am also not a regular user of it I use my REX very rarely and it never disappoint me.
I also noticed that I got approx 45mpg on REX.

 

[Arm]

This week I did an 820 mile round trip in span of 1.5 days in my 2018 94ah i3 REX. On second day (480 miles) I was caught in California atmospheric river torrential rain on multiple occasions. I was able to complete the 405 mile return trip in 7hr 45min thanks to REX. I could even shave another half hour if I had forgone two 20%-85% fast charging sessions.

I also drive a VW iD4 and have done the same trip with VW, and I am not sure I could have done it in the same time despite much larger battery.

The REX worked surprisingly well, even climbing Tejon pass at 65-70 mph I lost maybe 10% battery charge. I don’t use my REX too often but recently had an oil change and did the fuel additive/injector cleaner thing that the dealership recommended. Not sure if it had something to do with it.

One thing that I noticed is that once conditions are not ideal (rain, cold etc.) REX miles somehow appear longer than battery miles. I think I got around 45 mpg on REX.

I think it is a shame that BMW abandoned this technology in favor of larger and larger batteries. I for one would be willing to buy another REX if BMW or someone else (Mazda maybe?) comes up with an up with a compelling model.

Two things that I would improve is slightly larger gas tank (3 usable gallons instead of 2) and using engine heat for cabin heating.

Frankly I would have rented a car and not worried about it. 99.8% of the rest of the time I'd drive a pure EV. I don't see the point of lugging around a dead-weight almost all the time for that "occasional" need. But that's just my opinion. After having driven EVs for over 8 years now (and one plug-in hybrid...Volt), I am very happy with the fact that I don't have an engine to worry about...the oil, plugs, emissions, belts, gas station visits...etc.

 

[alohart]

Frankly I would have rented a car and not worried about it. 99.8% of the rest of the time I'd drive a pure EV. I don't see the point of lugging around a dead-weight almost all the time for that "occasional" need. But that's just my opinion. After having driven EVs for over 8 years now (and one plug-in hybrid...Volt), I am very happy with the fact that I don't have an engine to worry about...the oil, plugs, emissions, belts, gas station visits...etc.

I totally agree! I try to do all of the scheduled maintenance on my cars. I haven't owned a car with an ICE engine in the U.S. since 2012 and love not having to perform engine oil changes. I did have a Honda Insight hybrid at our apartment in Sweden until 2017, so I've been totally ICE-free for just over 5 years and will never buy a car with an ICE again.

 

[arodi3]

For me, the point of the REX is to allow the i3 to work as a fully capable car without a massive battery. I don't want to rent a car to go see a friend in a city a few hundred miles away.  I'd also like to bring my dog on those trips, which makes it more difficult to rent.  I think there are valid use cases for the REX and it annoys me that it is so often seen as an unholy copout.  There are environmental costs associated with these li-ion batteries.  While I am knowledgeable about the tradeoffs at the moment, I seem to recall that BMW looked into this when designing the i3, and was one of the reasons the i3 has such a limited range.  At about 280 lbs, the REX is not light, but it seems to me that a second rev could be lighter, especially if it was a ground-up redesign.  I think an "EV" with a built-in gas charger would be a great way to get people that need a car that "just works" to dip a toe in the EV world.  Many would never go back.  I think it is a shame that the series hybrid approach is so looked down upon.  

 

[agzand]

Frankly I would have rented a car and not worried about it. 99.8% of the rest of the time I'd drive a pure EV. I don't see the point of lugging around a dead-weight almost all the time for that "occasional" need. But that's just my opinion. After having driven EVs for over 8 years now (and one plug-in hybrid...Volt), I am very happy with the fact that I don't have an engine to worry about...the oil, plugs, emissions, belts, gas station visits...etc.

This was a paid business trip, so by driving my car I will get paid for the mileage (~$600). If I rent I won't get paid for the mileage and half a day that it takes to pick up/drop off the rental. So this one trip will pay for a few years of oil changes.

I have never had anxiety visiting a gas station. I actually enjoy the occasional break. These days when I visit a charging station in my other car (VW iD4) I have anxiety, how long I have to wait in line? Are all chargers broken? etc.

Ideally I would prefer a BEV with the same level of functionality as the REX, but unfortunately it doesn't exist yet, at least in sub $100k price point.

The other reason for having the REX is that the i3 and iD4 are our only cars and we live a in disaster prone area (earthquake). If there is an earthquake and power cuts off it will be easier to find gas than a charging station.

If we had an ICE car backup I would definitely pick the BEV.

 

[agzand]

For me, the point of the REX is to allow the i3 to work as a fully capable car without a massive battery. I don't want to rent a car to go see a friend in a city a few hundred miles away.  I'd also like to bring my dog on those trips, which makes it more difficult to rent.  I think there are valid use cases for the REX and it annoys me that it is so often seen as an unholy copout.  There are environmental costs associated with these li-ion batteries.  While I am knowledgeable about the tradeoffs at the moment, I seem to recall that BMW looked into this when designing the i3, and was one of the reasons the i3 has such a limited range.  At about 280 lbs, the REX is not light, but it seems to me that a second rev could be lighter, especially if it was a ground-up redesign.  I think an "EV" with a built-in gas charger would be a great way to get people that need a car that "just works" to dip a toe in the EV world.  Many would never go back.  I think it is a shame that the series hybrid approach is so looked down upon.  

I fully agree, and I expect in a year or two purist EV supporters will have to concede that we are long way (like two generation of cars) off from the technology and infrastructure that allows us to ditch ICE.

 

[Arm]

For me, the point of the REX is to allow the i3 to work as a fully capable car without a massive battery. I don't want to rent a car to go see a friend in a city a few hundred miles away.  I'd also like to bring my dog on those trips, which makes it more difficult to rent.  I think there are valid use cases for the REX and it annoys me that it is so often seen as an unholy copout.  There are environmental costs associated with these li-ion batteries.  While I am knowledgeable about the tradeoffs at the moment, I seem to recall that BMW looked into this when designing the i3, and was one of the reasons the i3 has such a limited range.  At about 280 lbs, the REX is not light, but it seems to me that a second rev could be lighter, especially if it was a ground-up redesign.  I think an "EV" with a built-in gas charger would be a great way to get people that need a car that "just works" to dip a toe in the EV world.  Many would never go back.  I think it is a shame that the series hybrid approach is so looked down upon.  

I fully agree, and I expect in a year or two purist EV supporters will have to concede that we are long way (like two generation of cars) off from the technology and infrastructure that allows us to ditch ICE.

Well I'm not a purist...I'm a realist. Many of you forget that almost ALL EV drivers...purists or not...drove ICE vehicles prior to owning EVS. The issue is many don't understand or can't bring themselves to change in the right way in order to use EVs properly.

It's a matter of the right tool for the right job. If I'm going to be hauling around a lot of things and need to tow or need a lot of space or need to go off-road, then yeah, an EV may not be the right tool for the job.

If I'm going out of town a few times a year and don't want to deal with crappy infrastructure, yeah I'll rent a car. It's simple enough for me and not a hassle.

But the advantages are huge the rest of time when driving my pure EV around. There are so many positives that those few negatives don't even register...for me.

I won't bring up the environmental issues because almost no one ever compares the cost of environmental damage the oil industry causes compared to the Li-Ion harvesting.