Use of REx engine

[Jeremy]

The reason I'm "beating it to death" is - it seems I'm only likely to get a test drive on a Bev in a couple of weeks and I'm pretty sure the dealer will be pressuring me to confirm my REx order and lock in the deposit.

I don't want to be left with a car which won't do the job I need it for - so I'm just trying to pick the brains of the more informed folk here to make a judgement.

Tom - do you agree with WT's opinion above that the REx motor, after efficiency losses, will only kick around 17kW into the battery and a 70mph highway cruise is likely to need about 20kW?

That's not a game changer for me since I still think that could make a round trip of up to 200/300 miles possible - as even 50% battery capacity could supply the 3kw shortfall for around 3 hours or 200 miles (with a refuel of course).

I'm just trying to get a feel for the likely limitations.

 

[williamtell]

Jeremy,

Please don't view my post as damning the REX option, but having read about some of the intricacies around the Chevrolet Volt solution I just wanted to share my thoughts on what limitations there might be.

Not having owed an electric vehicle or even a plug-in Hybrid, other members such as Tom has valuable experience to share, and it would also be highly unlikely that high ranking members of BMW would make statements which are untrue.

The proof will be in the pudding once the REX versions are available in general, and motoring publications and enthusiasts do extended runs in them.
I have a sneaky suspicion that if you leave the vehicle to its own devices, and only let the REX kick in at 20% - that you'll then might face some slight performance fall-off and overall limited range.
However, as others has stated there seems to be an option to let REX kick in at 80% - which means that 200-400 mile journeys at motorway speeds should be no problem.
I'll be really impressed if someone manages to do a 1000 mile roadtrip in 1 day in one of these though - but I guess that's missing the point.

Unless you really really need one right now, don't let a dealer pressurise you into a deposit until you have all the facts confirmed for yourself.
Or, you can always just ask the dealer in question to confirm on paper that you'll be able to do 200/300 mile journeys no problem

I just wish that it came with a 15-20l tank instead of a 9l one. Having to fill up every 160 miles will be a pain!
Can't wait to be able to view the car next Friday at my local dealer!

 

[Jeremy]

WT

No - I didn't think you were knocking it, your figures were useful & seemed realistic.

I'm just trying to build up my knowledge bank.

I've already put a deposit down - I'm just wondering whether to insist on a REx test drive.

I saw some tweets today from journalists driving the REx at the Silverstone press launch- so there are obviously some around in the UK.

 

[Sranger]

Here is the only thing I can say right now. My EV has the aerodynamics of a brick (literally). It can sustain 65mph on level ground at around 200amps at 120VDC or about 24Kwh. 70mph in my car requires about 280 amps. I think that the REx might be able to hold the state of charge in the 65-70mph since it is significantly more aerodynamic. A hilly area might cause some issues with the REx depending on the state of charge before it kicks in....

However, there is simply no way to know until more test results are in....

 

[ultraturtle]

I just wish that it came with a 15-20l tank instead of a 9l one. Having to fill up every 160 miles will be a pain!

If you are talking about highway speeds (70-75mph) my guess would be a fill up every 70 to 95 miles. I can't imagine the REx doing better than 40mpg at those speeds.

 

[TomMoloughney]

The reason I'm "beating it to death" is - it seems I'm only likely to get a test drive on a Bev in a couple of weeks and I'm pretty sure the dealer will be pressuring me to confirm my REx order and lock in the deposit.

I don't want to be left with a car which won't do the job I need it for - so I'm just trying to pick the brains of the more informed folk here to make a judgement.

Tom - do you agree with WT's opinion above that the REx motor, after efficiency losses, will only kick around 17kW into the battery and a 70mph highway cruise is likely to need about 20kW?

That's not a game changer for me since I still think that could make a round trip of up to 200/300 miles possible - as even 50% battery capacity could supply the 3kw shortfall for around 3 hours or 200 miles (with a refuel of course).

I'm just trying to get a feel for the likely limitations.

I have talked to people that have driven the REx at highway speeds for extended periods of time and I have spoken with i3 product managers. You can make a trip of 200/300 miles with it without worry. Now if you had three passengers, 200+lbs of cargo and needed to drive 50 miles up an 8% grade you may have difficulty. The range extender is in no way an "emergency only, limp mode generator" and I believe you will get proof of that soon.

 

[Sranger]

There is absolutely no new information in it, but here is an article about the i3 with a REx..

http://www.autocar.co.uk/car-review/bmw/i3/first-drives/bmw-i3-range-extender-first-drive-review

 

[Jeremy]

That's a very reassuring review for those of us who've ordered the REx version.

I was talking today to a BMW rep who has just returned from Leipzig and he said their technical people told him the REx motor was set up to maintain the state of charge at the time of engagement - but not to improve on it. He said this was to stop people charging from the engine rather than a power outlet. I guess this is a sop to the green lobby.

He also said the motor was barley audible from inside the car and could be used indefinitely.


So i think it's all looking positive for the REx.

 

[williamtell]

http://www.telegraph.co.uk/motoring/car-manufacturers/bmw/10440292/BMW-i3-Range-Extender-review.html

Seems like you do need to take a bit of precaution and engage REX long before the battery runs flat if you're going to be traveling long distances.
Otherwise you might end up crawling along at 45-50mph.

Went to the launch on Friday, impressed with the design and look of the car.
Will be going on a test drive on a all electric version tomorrow.

 

[russtyjames]

Having just driven the REX around 100 miles on a flat battery (<3 mile range) it didn't once restrict my speed. Maybe I wasn't driving fast enough, I was doing slow motorway/ city driving into London. The noise was definitely audible at slow/high speeds when and if the engine was working hard,for my drive around 10%-20% of the time. The Rex also uses stop/start technology and will switch the engine off below 10mph or when you stop at traffic lights etc.

 

[williamtell]

Thanks for the info James, I'm sure situations like in the review would be the exception, rather than the rule!

 

[Bmachine]

The Rex also uses stop/start technology and will switch the engine off below 10mph or when you stop at traffic lights etc.

That is odd. In this case the engine is used to charge the battery so why would it need to use start/stop ? Just for noise?

 

[Jeremy]

So what a dealer told me is true - you can't build up charge by driving carefully with the REx on.

Therefore if you're using a motorway between two urban journeys, you need to fire up the REx at around 50% to keep some power in reserve for the last all-electric urban stretch.

Sounds good.

 

[russtyjames]

I found you could add maybe 2 miles to the range with the rex running by using the re-gen brakes, this can then be used to the pull the car away silently at traffic lights. I guess they have implemented stop start technology to further improve the emissions and also reduce the noise.

 

[Jeremy]

I'm slightly alarmed by this Telegraph review which seems to be the only one for a journey of well over 100, mainly motorway, miles.

http://www.telegraph.co.uk/motor...w/10440292/BMW-i3-Range-Extender-review.html

Admittedly, the guy seems a bit of a wally for running it straight down to 5% on his outbound journey, rather than running the REx at 50% or so - but it does seem a bit alarming that he had to slow down to 40mph on the return journey.

Seems that my regular 300 mile return journey to London may be impractical.

I had almost convinced myself I wouldn't need to keep another car.

 

[Sranger]

I'm slightly alarmed by this Telegraph review which seems to be the only one for a journey of well over 100, mainly motorway, miles.

http://www.telegraph.co.uk/motor...w/10440292/BMW-i3-Range-Extender-review.html

Admittedly, the guy seems a bit of a wally for running it straight down to 5% on his outbound journey, rather than running the REx at 50% or so - but it does seem a bit alarming that he had to slow down to 40mph on the return journey.

Seems that my regular 300 mile return journey to London may be impractical.

I had almost convinced myself I wouldn't need to keep another car.

I am not sure I completely believe this review. The author is NOT an EV fan and this review seems to contradict all other reviews I have seen. He admitted that he was driving 70+ mph much of the time. It reminds me of the New York Times report of the Tesla Model S. I do think that you can drive these cars in a manner to cause issues with the REx power generation. I am just not convinced that these would be real world issues that an educated driver would have.

I think he had to work hard to get the results of his pre-conceived notions of the car...

 

[m11wlk]

The Telegraph journalist mentions that his electric range is 49 miles when he sets off on the 60 mile journey to Folkestone to see if he can make it... then he hits the AC in November, turns on the headlights during the day and hopes for rain (where's my raised eyebrow emoticon?)

Still, I enjoyed another video

 

[kentheteaman]

I do think that you can drive these cars in a manner to cause issues with the REx power generation. I am just not convinced that these would be real world issues that an educated driver would have.

I think he had to work hard to get the results of his pre-conceived notions of the car...

I agree.
I took it for a test drive down the motorway. Rex performed very well and I was able to reach 75miles/hour and no trouble.

Having said so I have not tried a sustained 75mls/h for a long time. But for real world driving I never drive 75mls/hour or more speed for a long time. 60 or 65mls/h is my comfort level and I can not see any issues with Rex for that kind of speed.

regards,
ken