Surge
Posts: 256
Joined: Fri Apr 25, 2014 5:11 pm
Location: Toronto, ON

Re: Why would anyone get the REx in the US?

Fri May 16, 2014 8:41 pm

Here's the big problem with the REx - at least in my case, I realized I'm only going to need it when driving on the highway.
When do I drive more than 80 miles in the city in a day?? Never.

And it's on the highway that the REx reportedly doesn't do very well. I'm referencing the Telegraph UK article:
"I thrummed along at 70mph, but it soon became clear that at this kind of speed our comfortable range between fill-ups was more like 40-50 miles."

It's not an option for me to drive below 70 mph - and I think doing so, at least here in the north-east, or west coast, is dangerous. No one really drives 55 mph! So cruising at 70-80 mph is the norm that the i3 needs to maintain.

At this speed, and then adding cold weather (0F) - which by others' estimates will reduce range by over 50% - you are looking at 20 (winter) - 50 miles of highway range on the REx.

So if you need to drive 70-80 mph on the highway, you're not going to get more than 20-50 miles on the REx tank. You'll need to fill-up - at best - every 30 minutes!

So that's a real bummer…. And compounding this, for US/Canada, the REx only comes on when SOC is 6%. So here's what the Telegraph article said about that:
"...but once the charge runs down to five or six per cent and the range extender cuts in, if you keep driving at 75-80mph it can’t maintain the charge.”

So now you must reduce speed below avg highway cruising speed…

Putting this all together, if you're in the US/Canada, the REx will give you +40-50 highway miles, if you drive < 75mph… and maybe not uphill.

To me, it's just not worth buying the REx in that case, and lugging it around everywhere you go, and reducing the battery's effective useable range by 10-30% (depending on how you look at the efficiency advantages of the BEV).

I just don't know if the BEV alone will work either… in very cold weather I'm worried the range will be something like 20-30 miles.

Hmmm…. I love the i3 but living in cold climates and needing it for highway driving may not be a good fit, REx or no REx. :o
NOT- Soon to be ordered:
i3 • Lodge interior • Tech package • DC fast charge • gray or white

fdl1409
Posts: 154
Joined: Sun Feb 23, 2014 1:37 am
Location: Germany

Re: Why would anyone get the REx in the US?

Fri May 16, 2014 11:45 pm

Your estimates are all too pessimistic. With the REx, you can reportedly drive 120 km/h ( 75 mph ) on the motorway while holding charge. In the winter, you need heating. But in comparison to driving more slowly, the heating will eat up a smaller percentage of power, because heating at 75 mph is not that much more than at 40 mph. Lets assume heating needs 3 kW, that leaves 20 kw for the motor, which is still enough for 70 mph. Battery is warm, because you have preheated this and emptied it in a comparatively short time, so why should the range drop as dramatically as you have suspected? Most of the reduced winter range is due to heating and cold battery. Battery won`t get cold on a long fast trip, and heating alone reduces range less if you drive faster.

The REx can only empty the tank in a certain time which is the same in hot and cold weather. It can produce 23 kW, and that will be the same in cold conditions. The time in which the tank will be drained at max power is the same, only maximum speed and range covered will be reduced, but not anywhere near as much as you believe.

Frank
Germany
BMW i3 REx

Surge
Posts: 256
Joined: Fri Apr 25, 2014 5:11 pm
Location: Toronto, ON

Re: Why would anyone get the REx in the US?

Sat May 17, 2014 5:58 am

Thanks Frank. It makes sense, what you wrote; but I got my information from others… so some people really believe those very pessimistic numbers.

This is causing some frustration -- widely varying reports on what the range is and is not.
NOT- Soon to be ordered:
i3 • Lodge interior • Tech package • DC fast charge • gray or white

bxb40
Posts: 51
Joined: Tue Mar 18, 2014 8:00 pm

Re: Why would anyone get the REx in the US?

Sat May 17, 2014 6:17 am

[quote="fdl1409"]"Battery is warm, because you have preheated this and emptied it in a comparatively short time, so why should the range drop as dramatically as you have suspected? Most of the reduced winter range is due to heating and cold battery. Battery won`t get cold on a long fast trip, and heating alone reduces range less if you drive faster."

Actually, the worst case is when trying to get back home at the end of the day - the battery is cold at -25C and has about 60% SOC from getting to work in the morning (unless you have a charger at work that most in US do not, the wind is blowing snow, the roads are icy so you cannot do any speeds above 40mpg (the only good thing in this scenario). It takes you 3-4 hours to get home instead of 40 minutes - most stop-and-go, but you need to run the heater all the time. The battery never warms up due to stop-and-go plus the low temps outside. And yes, you have 2 extra people in the car (because you have such a cool and efficient car, that will start at very low temps and drive well in the snow (on Blizacks), everybody wants to carpool with you :) )

[quote="fdl1409"]"The REx can only empty the tank in a certain time which is the same in hot and cold weather. It can produce 23 kW, and that will be the same in cold conditions. The time in which the tank will be drained at max power is the same, only maximum speed and range covered will be reduced, but not anywhere near as much as you believe. "

True - but the ratio of energy used for propulsion vs heating and losses on the cold battery will make for a shorter REX range in winter, like you say. However, the energy consumption being higher, the REX will work at the highest RPMs where it is not as efficient, so you are losing some mpg because of that - experience will say how much, no way of estimating yet for US (in EU one will activate the REX sooner, i.e. at 40% SOC, so it does not have to run at max RPMs while allowing for SOC to slowly drop...). But you can top the REX off using an emergency gas can of 2 gl. you keep in the frunk for such conditions :) Try that with the BEV...

bwilson4web
Forum Supporter
Posts: 533
Joined: Fri Apr 29, 2016 11:59 pm
Location: Huntsville, AL

Re: Why would anyone get the REx in the US?

Sun Apr 15, 2018 1:53 am

tiburonh wrote:The REx in the US now seems to me to be pretty much a waste of money. A waste of $3,850 (plus tax) to be exact. Things going against it:
. . .


1. CARB credits and HOV stickers - not really a problem in Alabama.

2. CA HOV stickers - ditto.

3. Enabling REX - there are at least three known coding systems to code the BMW i3-REx to tailor to my needs in Alabama.

4. Usable gas tank - coding solves the problem although I've only seen 2.3 gallons.

5. Increases 0-60 time - my other car is a Prius.

6. REx noise - use it on the highway and it blends in with the road noise.

Surge wrote:I feel quite strongly about this, . . .


1) 81 mile BEV EV range.

2) 72 mile REx EV range - (81-72) / 81 = 11.1% loss of EV range

3) The EPA measures the EV range so the 72 miles is a hard metric.

4) The EPA measures and reports the range as 150 miles, a hard metric.

5) Freezing weather performance - my other car is a Prius Prime and has worse problems at temperatures under 50F. The problem being the ICE will start for a number of poorly defined conditions. In contrast, a coded BMW i3-REx has reproducible behavior. The REx is my first choice in cold weather.

"if you don't drive on the highway" - bought mine 463 miles away and was home without charger delays.

"if you don't drive in cold (below freezing) temperatures" - it is our first choice below 50F because our other car is a Prius Prime.

"if your daily commute/travels are more than 80 miles but less than 120 miles" - retired, not my problem.

Coding to EU standards solves a lot of problems. Living in Alabama, we're relaxed about such things.

Bob Wilson
20k/27k mi 2014 BMW i3-REx
10k/10k mi 2017 Prius Prime

viking79
Posts: 29
Joined: Wed Apr 16, 2014 3:04 pm

Re: Why would anyone get the REx in the US?

Sun Apr 15, 2018 5:31 am

I agree Bob, also, from what I noticed when I bought my used i3 REx, they were selling for maybe $3,000 more at 3 years old, so buyers would get most of their money back on that feature. That feature seemed to have better payback than the trim levels or tech package.

ultraturtle
Posts: 439
Joined: Sun Dec 30, 2012 11:17 am
Location: Peachtree City, Georgia USA

Re: Why would anyone get the REx in the US?

Sun Apr 15, 2018 6:34 am

Funny how 4 years have passed, and nothing much has changed. The i3 REx, along with the Volt and PiP, remain the only serious EVs with unlimited range.

Unlike vehicles limited to their battery range, a range extended EV can serve as your only vehicle. The embedded energy and associated environmental impact of a second vehicle to carry you on trips a mile or more beyond your battery range (no matter what that range may be) is a massive waste. Add to that the fact that the first 120 miles or so of any such trip can be powered by electricity in a REx. Not so much in a dinosaur powered vehicle.

bwilson4web
Forum Supporter
Posts: 533
Joined: Fri Apr 29, 2016 11:59 pm
Location: Huntsville, AL

Re: Why would anyone get the REx in the US?

Sun Apr 15, 2018 1:49 pm

ultraturtle wrote:Funny how 4 years have passed, and nothing much has changed. The i3 REx, along with the Volt and PiP, remain the only serious EVs with unlimited range. . . .

A minor technical point, the EPA web site lists 31 plug-in hybrids: https://www.fueleconomy.gov/feg/PowerSe ... 0&pageno=1

Just I get the impression some are marginal. Now I'm not a fan but Hyundai and Honda appear to have serious plugin hybrids.

ultraturtle wrote:Unlike vehicles limited to their battery range, a range extended EV can serve as your only vehicle. The embedded energy and associated environmental impact of a second vehicle to carry you on trips a mile or more beyond your battery range (no matter what that range may be) is a massive waste. Add to that the fact that the first 120 miles or so of any such trip can be powered by electricity in a REx. Not so much in a dinosaur powered vehicle.

Excellent point about having by whatever means, purchase or rental, of a second gas vehicle just for long distance trips. As our BMW i3-REx shows, a small ICE and its generator have a really modest impact on vehicle EV performance.

Bob Wilson
20k/27k mi 2014 BMW i3-REx
10k/10k mi 2017 Prius Prime

jadnashuanh
Posts: 3761
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Why would anyone get the REx in the US?

Mon Apr 16, 2018 4:56 pm

viking79 wrote:I agree Bob, also, from what I noticed when I bought my used i3 REx, they were selling for maybe $3,000 more at 3 years old, so buyers would get most of their money back on that feature. That feature seemed to have better payback than the trim levels or tech package.

The REx's retail cost is over $3K ($3850 on MY2018), so the vehicle's depreciation is about the same if the BEV is about $3K less...
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

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