Rex Owners - Miles before auto REX in UK

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uktechie

Well-known member
Joined
Mar 23, 2014
Messages
113
Location
UK
Can any actual owners tell us what on average miles they are getting before the REX automatically switches on? From what I have read it is when battery is 5% so am I correct to assume you are getting 60-70 miles on electric before auto extender kicks in?
 
I recognize that this is difficult to answer. However, my commute is about 76 miles. If I were to purchase an i3 REX, will I have to fill up the tank all the time since REX will kick in every day? Or will it just kick in on some days depending on traffic, weather, etc?

I know there are a lot of variables, but should I just avoid buying the i3 REX or is it a viable solution for a 76 mile commute without having to fill the tank twice a week?

Any recommendations about how I can make a decision?
 
At 76-miles, unless you can charge while at work, or are willing to spend the time to charge on the way home, means that a REx is your more viable option. Personally, I think you are on the edge of range where the i3 is a viable option. But, on a 'good' day, you may not engage the REx, but it would be there should you need more heat or a/c or get stuck in traffic to get you home without stopping. It might be viable to keep say a 5-gallon can of gasoline at home, and that would mean you may not need to actually stop at a gas station for a week or more.
 
RJBarry said:
I recognize that this is difficult to answer. However, my commute is about 76 miles. If I were to purchase an i3 REX, will I have to fill up the tank all the time since REX will kick in every day? Or will it just kick in on some days depending on traffic, weather, etc?

I know there are a lot of variables, but should I just avoid buying the i3 REX or is it a viable solution for a 76 mile commute without having to fill the tank twice a week?

Any recommendations about how I can make a decision?

I can share what we made our decision on. We have not received our i3 yet and made the decision to buy a REX based on 2 test drives covering our round-trip work commute.

Our daily commute is 72 miles round trip. (edit: this is 35 miles motorway/highway and 37 miles secondary roads; at commuter times, we average just 32 mph for the entire trip due to traffic; on the motorway/highway, we never really exceed 60mph due to traffic) On our first test drive, I explored the capabilities of the car and was not frugal at all. Even so, I managed to get 1 mile away from home before the REX turned on. For the 2nd test drive, I arrived home with an estimated 11 miles battery range remaining with no REX used. This was with driving how I would normally on a daily basis, at commuter speeds.

We decided on the REX over BEV based on the above because even 11 miles range remaining on the 2nd trip invoked a bit of "range anxiety". The reality of our lives is that 2-3 times per week need to go an additional 5-10 miles in the evenings (meet friends for dinner, go to the gym/pool, etc.). I sometimes run an errand or two during my lunch break at work, as well. That kind of mileage means we needed more range--and the REX is how we achieve that with the i3. At about 40 mpg efficiency on the REX, we were OK with that as >90% of our mileage will still be electric.

If the i3 could have delivered a solid 100 mile battery range, we would have gone with BEV. As it can't, REX is the way to go for us.

edit: I added in what our mileage looks like in-line above.
 
I have an i3 REx. Mostly driving country roads with 50 mph and urban. Lots of mountains. My max. range so far was 151km ( 94 miles ) with 29km ( 18 miles ) remaining. More would be possible when driving longer distances and fewer mountains. I am sure I can always drive at least 100 miles in the summer before the REx kicks in. This will be less if speed is higher.

Frank
 
Thanks everyone for the feedback!
elptex said:
Our daily commute is 72 miles round trip. (edit: this is 35 miles motorway/highway and 37 miles secondary roads; at commuter times, we average just 32 mph for the entire trip due to traffic; on the motorway/highway, we never really exceed 60mph due to traffic) On our first test drive, I explored the capabilities of the car and was not frugal at all. Even so, I managed to get 1 mile away from home before the REX turned on. For the 2nd test drive, I arrived home with an estimated 11 miles battery range remaining with no REX used. This was with driving how I would normally on a daily basis, at commuter speeds.
Thanks elptex, this is very similiar to my commute. If I am reading this right, you are able to reliably complete a 72 mile round trip without REX turning on. So you don't use a lot of gas, but have it when you need it. Which is what I am looking for. During the school year, my commute is about 6 miles shorter, which is 72 miles. I agree that I would only consider the REX, the BEV is not going to work for my situation. I'm just trying to figure out if even the REX would work for me or I should settle for a hybrid (which would make me sad since I really like the i3 :))

How are you arranging these "test drives"? I asked my dealership whether I could take the car on my normal commute and they balked. No dice so far.

fdl1409 said:
I have an i3 REx. Mostly driving country roads with 50 mph and urban. Lots of mountains. My max. range so far was 151km ( 94 miles ) with 29km ( 18 miles ) remaining. More would be possible when driving longer distances and fewer mountains. I am sure I can always drive at least 100 miles in the summer before the REx kicks in. This will be less if speed is higher.
Frank
To be clear, Frank, you are saying that you went 94 miles before REX kicked in? With mountains! That makes me feel a little better.

I forgot to add earlier that I live in Southern California (so nice weather) but have 2 mountain grades on my commute. Given that it is near Los Angeles, when the highway is moving, it is moving fast (70+ mph) but often it isn't moving much at all, LOL! I'm reading between the lines above that I would be better off driving slowly and I would get more mileage. I don't mind adjusting my driving style if it means being pure electric.
 
RJBarry said:
Thanks everyone for the feedback!

How are you arranging these "test drives"? I asked my dealership whether I could take the car on my normal commute and they balked. No dice so far.

I'm in the UK and have simply asked our local dealer (Reading Cooper BMW). They have been great, I highly recommend them. They noted with me that the majority of their customers want to do extended/overnight test drives to double-check the real-world viability of them having the i3 as their primary vehicle. If it sells a car, its worth it and they understand that.
 
We placed an order with Dick Lovett Bristol on the day we took the test drive - we only went there to see the new motorcycle range! I got home and thought "what have I done, I don't do electric vehicles!" We regularly drive to Plymouth using a Golf GTi or 330Ci and I was concerned that the i3 would not be up to the journey, or that I would have to limit my speed, which I was not prepared to do. The i3 is to replace the brilliant but ageing Golf. I asked the dealer (Scott Martin - a really knowledgeable and helpful guy) if I could borrow a Rex for a run to Devon. It is a little more complicated than usual because the car belongs to BMW, not the dealer, but he very quickly checked it out and arranged for us to have one from Saturday afternoon until Monday morning. We actually only went as far as my father's in Newton Abbott but it showed that the car is more than capable of handling the journey, albeit mainly on Rex and at "normal" motorway speeds. The drive wiped out all of my concerns and we even upgraded the order. We placed the order in mid March (missing the free Professional upgrade - damn it) and were told it would be a September delivery, which slipped to October and then (after the spec upgrade) to November but, partly thanks to Scott, is now showing late August, but we hope to get it on 1 September. If BMW can get people to drive the car they will sell more, so I don't see why they would say no. I was ready to cancel if I did not get the extended test.
 
@RJBarry,

yes, I drove 94 miles.
No, REx did not kick in. I could have gone approximately another 10 miles before the REx would have started.

With present charge I have 81.8km ( 51 miles ) with 54% SOC remaining.

Frank
 
All of this feedback is great! The data points here are great.

I'm annoyed with my BMW dealership, after multiple requests they are still saying I can't have an extended test drive. :evil:

However, based on feedback here I'm still leaning towards getting the i3+REX.

Please tell me if you think I'm crazy.

Summary of assumptions:

0. Given a 72-88 mile commute with hills in nice weather:
1. It is most likely that I will be able to go at least 1-2 weeks between fill-ups
2. There is a low probability (hard to estimate exactly) that I would have multiple fill-ups a week
3. There is also a probability (also hard to estimate) that I would have to fill-up less

Additional observations:

A. My commute range is within the abilities of the i3, it will be my driving style and max speed that most affect how often I have to fill-up
B. Living in a warm climate is significantly in my favor
C. The two moderate mountain grades in my way are not great, but not the end of the world either
D. The recommendation to keep a 5 gallon gas can in my garage to even things out is a great idea

Let me know if I'm missing something obvious... and thanks again for all the feedback!
 
RJBarry said:
Let me know if I'm missing something obvious...
Recommend you factor in a loss of ~20% battery (range) capacity over the course of 8 years and 100,000 miles of driving. BMW warranties the battery pack for a 30% loss at that point, and engineers predictably design for failure at 150% load.
 
ultraturtle said:
Recommend you factor in a loss of ~20% battery (range) capacity over the course of 8 years and 100,000 miles of driving. BMW warranties the battery pack for a 30% loss at that point, and engineers predictably design for failure at 150% load.
Ouch! :shock:

So if the REX was kicking in at between 70 and 90 miles, after 100,000 miles it might kick in between 56 and 72 miles. That is a big hit.

This commute is about 18,000 mi/yr, so I'll hit 100,000 in closer to 5 years. My fuzzy math predicts that I'll be filling up approx. every 3 days given those numbers.

Dang, you may have ruined my weekend. Thanks for the food for thought. I think I'll have to wait on getting an EV until there are just more charging options at my places of employment. Round trip just isn't seeming feasible. :cry:

Edit:
Just found this online... boy this is like gambling isn't it? Maybe I'm just not the earler adopter type. We'll have to see if I have the guts.
http://www.designnews.com/document.asp?doc_id=261882 said:
If managed properly, and if the car’s manufacturer incorporates a good, active cooling system, lithium-ion EV batteries should operate much more than eight years before finally losing more than 20 percent of their original power. The truth won’t be known, however, until lithium cells have been on the road for a couple decades, Cugnet said.
Edit 2:

Or I just factor in that the gas savings will pay for a new battery, but in the meanwhile I put out significantly less carbon emissions. We'll have to see how altruistic I am as well, LOL
 
The batteries in the Prius have been lasting much longer than originally prophesied. It really depends, I think, on your particular situation, the local weather conditions, and your use patterns. BMW's warranty is probably written so that they do not need to honor it for most people, otherwise, they'd be losing lots of money. IOW, it is a conservative, worst-case situation...most people should never need it.
 
RJBarry said:
Dang, you may have ruined my weekend. Thanks for the food for thought. I think I'll have to wait on getting an EV until there are just more charging options at my places of employment. Round trip just isn't seeming feasible. :cry:
Please don't put off the decision to purchase an EV based on a simple 20% fudge factor! Think it through. Every 72-88 miles you drive using gasoline for the next umpteen years until you commit to an EV are miles of opportunity lost. Wish I knew where you lived (please update your profile), because most of Europe and bits of Southern California are taking charging infrastructure seriously.

Worst kept secret of environmental responsibility is that battery electricity is a fantastic way to move people around for short distances, and a horrible way to move them over long distances. Similarly, gasoline is an incredibly stupid fuel for short distances, but actually makes sense for longer hauls. It'll take us all a few decades to figure it out, but we'll get there.
 
While I do occasionally drive further than the i3 can take me easily, for 90% of my daily (if that) driving, it is more than sufficient, and actually better, since on my other ICE, in my typical daily use, it never gets fully warmed up. Now, I don't worry about short hops since the biggest hit on economy is conditioning the battery and interior, and that can be done without the wear and issues with idling an ICE, and doesn't hurt the range, if done while on the EVSE.
 
ultraturtle said:
Wish I knew where you lived (please update your profile), because most of Europe and bits of Southern California are taking charging infrastructure seriously.
Updated. I'm commuting from Ventura County to Los Angeles. My commute varies based on whether I'm dropping off my son and if I'm trying to avoid traffic, thus the 75-88 mi range (yes, sometimes it is worth it to go 10 miles out of my way to avoid gridlock.)

The part of LA where my office is has 0 charge points at the moment. Closest one is a BMW dealership 5 miles away, and the rest are much further.
ultraturtle said:
Worst kept secret of environmental responsibility is that battery electricity is a fantastic way to move people around for short distances, and a horrible way to move them over long distances. Similarly, gasoline is an incredibly stupid fuel for short distances, but actually makes sense for longer hauls. It'll take us all a few decades to figure it out, but we'll get there.
Agreed, but the question at hand is just how long "short distances" are. Specifically for the i3 with REX, does 75-88 miles qualify? I know it can do it, but I don't want to be stopping for gas every 2-3 days.
 
RJBarry said:
Agreed, but the question at hand is just how long "short distances" are. Specifically for the i3 with REX, does 75-88 miles qualify? I know it can do it, but I don't want to be stopping for gas every 2-3 days.
Doesn't really matter that much. Say you get only 70 miles EV and 12 miles of gasoline range per trip. You'd have to refuel every 6 days, but you would be driving 420 miles on electricity rather than gasoline over the course of those days, saving a tremendous amount of both greenhouse gasses and pollutants, considering California's relatively clean electricity grid.
 
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