Chrisn
Posts: 136
Joined: Wed Aug 13, 2014 3:16 pm

US i3 Rex dangerous when climbing hills

Wed Aug 13, 2014 3:39 pm

Hello.

I picked up my BMW i3 REX yesterday. I live in the SF Bay Area (North-east corner). I frequently travel to the beach near Santa Cruz, CA via Highway 17 (for those who may be familiar with the area). I feared that this could be a challenge for the i3 as the base of the hill over to the beach is about 60 miles away from home (meaning battery could run out before climbing the hill).

Let me start by saying I knew that REX mode has some power limitations, and I don't expect to use the REX in daily commuting. But this is a trip I make every couple of weeks. I saw no definitive info from BMW on the nature of the REX limitations, but had read online that you could cruise at 75MPH on flat ground and that it would maintain 45-50MPH on grades. The speed limit on Highway 17 is 50 MPH, so I felt like even the worst case would be tolerable. I was wrong.

After the ICE kicked on, the car maintained speed for maybe 5 minutes, then began to feel very weak. On the next uphill section, my speed fell quickly from 50MPH down to 25MPH and was falling (this while at WOT). Cars backed up behind me and I needed to put on the hazard blinkers and crawl to the next turn out.

I waited on side of road while the engine continued to run (but seemingly not at full load). I did not know how long to wait. After 3-5 minutes, I attempted to merge back into traffic (I was still on an uphill section). The car initially had good power, accelerated to ~40MPH, then crapped out and fell back to 25MPH. I crawled to next turnout and waited 10 mins. That was enough to get me over the next hill and get me on my way.

This wasn't just annoying. It was dangerous.

Is there any way for US owners to force on the REX early to preserve charge? The Chevy Volt has this even though the ICE by itself can still maintain speed.

Any advice (beyond finding a charging station at the base of the hill and wasting a couple of hours)? Perhaps when the DC fast charge network is built, a 15-20 minute coffee break wouldn't be too bad. But for now I am at a loss.

jadnashuanh
Posts: 4470
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: US i3 Rex dangerous when climbing hills

Wed Aug 13, 2014 4:21 pm

There is no currently available way to force the REx on earlier in the NA market (at least in the USA and Canada...not even sure if they are selling it elsewhere in NA yet).

The car will go into battery preservation mode at (if I remember correctly) 1.9% on the REx, and the REx won't come on until it's around 6.5%, so if you are stressing things (i.e., using more power than the REx can provide), you will continue to draw down the battery reserve and eventually hit that brick wall.

The only way around this is to either find a charging station to top off, forego some of the creature comforts - switch to Eco Pro or Eco Pro+ mode earlier on in the trip, and maybe take advantage of all of the prompts to help you go more economically, or, take a different vehicle or route.

I'm been saying this on this forum for awhile...it really depends on where and how you drive whether the car, BEV or REx will work out for you. It is designed as a city, commuter car, and at that, it does well.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

Zzzoom3
Posts: 214
Joined: Thu Jul 10, 2014 1:39 pm
Location: Ventura, CA

Re: US i3 Rex dangerous when climbing hills

Wed Aug 13, 2014 4:30 pm

There has been much debate about such a scenario on this forum in recent weeks. Much of it centered about just how much power the REx really delivers and how it affects performance when you get into this very low SOC battery scenario. Yours is the 1st post from someone, as far as I know, that has actually encountered it.

BMW has limited when the REx will operate in the U.S. so it meets the guidelines which qualifies it to CAFE standards and obtains the most credit even though it has a range extender. I think the category is BEVx or something similar.

Next time you know you'll need to arrive at the hill with a higher SOC prior to ascending. It will be interesting to find out just how much SOC you need to have available in order to make it at "normal" speed.
  • - I'm curious if you had the vehicle in Comfort Mode while you were traveling to and up the hill?
    - What was your SOC was when you got to the beginning of the climb?
    - Did you expect to arrive with little or no charge and that the REx would get you up the hill or were you sort of experimenting?
    - What was the SOC at the start of the climb?
Last edited by Zzzoom3 on Wed Aug 13, 2014 5:08 pm, edited 2 times in total.
Lou Perez
2005 E46 M3 Dinan Titanium Silver
2012 Volt Diamond White Tricoat
2014 i3 BEV Giga Laurel Grey Electronaut

jadnashuanh
Posts: 4470
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: US i3 Rex dangerous when climbing hills

Wed Aug 13, 2014 4:37 pm

FWIW, even if you could turn the REx on earlier, if you drive far enough under those circumstances, you could run into the same problem. With your total distance being fairly reasonable, if you could have turned it on early like they can outside of NA, you may not have run into this situation, but it's always there if you're stressing the thing once the SOC gets low enough. THe car has a strong will to survive! It will not let you dangerously discharge the batteries beyond a certain point, and that's true with both the BEV and the REx - you'll hit the same brick wall, it's just that the levels are different, and if you then can drop your load, the REx can recover on its own, the BEV cannot without a stop to recharge somewhere. This can be critical, but the results are not a secret.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

Zzzoom3
Posts: 214
Joined: Thu Jul 10, 2014 1:39 pm
Location: Ventura, CA

Re: US i3 Rex dangerous when climbing hills

Wed Aug 13, 2014 5:22 pm

jadnashuanh wrote:and if you then can drop your load, the REx can recover on its own
What do you mean "drop your load". Keep it clean man! :lol:

Seriously though, what electrical load would you be dropping? The car has already dropped whatever load it can. There ain't anymore to shed? It's not Apollo 13 with Mission Control coming up with some workaround for you behind the scenes! And by "recover on its own" I presume you mean running the motor in order to recover some SOC but that only works until you run out of gas!

Best course of action is to make sure you've got enough juice in that high voltage battery pack before you get going up the climb me thinks ;)
Lou Perez
2005 E46 M3 Dinan Titanium Silver
2012 Volt Diamond White Tricoat
2014 i3 BEV Giga Laurel Grey Electronaut

jadnashuanh
Posts: 4470
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: US i3 Rex dangerous when climbing hills

Wed Aug 13, 2014 5:49 pm

Load, as in draw on the battery, as in shut off things that aren't keeping the vehicle moving such as the a/c, fans, radio, etc. - anything you can that will reduce the load/draw on the batteries, that will keep you going further.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

RJBarry
Posts: 42
Joined: Wed Jul 16, 2014 3:09 pm
Location: Ventura County, CA

Re: US i3 Rex dangerous when climbing hills

Wed Aug 13, 2014 6:02 pm

Same exact thing happened to me. I was do a fairly long round trip and ran out of electric just about the midway point. On the way back I had 3 long grades. Admittedly, I wasn't really paying attention and, though the car was in ECO mode, I was probably going a little over 70 maybe and had the AC on.

On the first grade I noticed that the high-end blue and grey bars started to disappear from the "performance display" in my console. Once they caught up with the white indicator of my current performance, the car started to drastically loose power. When all of the bars on the right hand side had disappeared, the car had exactly NO power. I had it floored and it just kept loosing speed. Just as the original poster, I had my flashers on, but felt that I had to pull over once my speed got too low.

I noticed on the blue charge bar there is a little triangle that indicates just a little bit of charge. The bar was showing no charge at all when I pulled over. However the REX continued to chug and once the charge in the blue bar built back to the little triangle, then the bars on the performance bar started to come back. Once all the performance bars were back, I managed to pull back into traffic and get up and over the hill.

On the next two hills, as I approached them I proactively put it in ECO pro+ mode, turned off the AC altogether and started the grade at 55 (to the annoyance of other drivers since the speed limit is 65) and while some of the performance display bars started to disappear, they never caught up to my white indicator, so I never lost any power/speed. I just got a little warm since there was no AC.

That first hill was pretty scary though.

Zzzoom3
Posts: 214
Joined: Thu Jul 10, 2014 1:39 pm
Location: Ventura, CA

Re: US i3 Rex dangerous when climbing hills

Wed Aug 13, 2014 6:30 pm

jadnashuanh wrote:Load, as in draw on the battery, as in shut off things that aren't keeping the vehicle moving such as the a/c, fans, radio, etc. - anything you can that will reduce the load/draw on the batteries, that will keep you going further.
The car does this whether you want it to or not below 1.9% relative SOC ...
Lou Perez
2005 E46 M3 Dinan Titanium Silver
2012 Volt Diamond White Tricoat
2014 i3 BEV Giga Laurel Grey Electronaut

MarkN
Posts: 89
Joined: Thu Oct 31, 2013 12:45 pm
Location: Fort Collins, CO USA

Re: US i3 Rex dangerous when climbing hills

Wed Aug 13, 2014 6:34 pm

Chrisn wrote: ...
Is there any way for US owners to force on the REX early to preserve charge? The Chevy Volt has this even though the ICE by itself can still maintain speed.

Any advice (beyond finding a charging station at the base of the hill and wasting a couple of hours)? Perhaps when the DC fast charge network is built, a 15-20 minute coffee break wouldn't be too bad. But for now I am at a loss.
At http://www.mybmwi3.com/forum/viewtopic. ... 6&start=40 I posted instructions on how to turn on "Exhaust-gas test mode" that will force the REx to run for up to 20 minutes with the important limitations that the rear hatch has to be open and the car must be stopped. You could try this and see if it lets you charge the battery enough to complete the hill.
2015 i3 REx

Zzzoom3
Posts: 214
Joined: Thu Jul 10, 2014 1:39 pm
Location: Ventura, CA

Re: US i3 Rex dangerous when climbing hills

Wed Aug 13, 2014 6:35 pm

RJBarry wrote:I noticed on the blue charge bar there is a little triangle that indicates just a little bit of charge. The bar was showing no charge at all when I pulled over. However the REX continued to chug and once the charge in the blue bar built back to the little triangle, then the bars on the performance bar started to come back. Once all the performance bars were back, I managed to pull back into traffic and get up and over the hill.
I'm wondering if you ever got any range warnings?
Lou Perez
2005 E46 M3 Dinan Titanium Silver
2012 Volt Diamond White Tricoat
2014 i3 BEV Giga Laurel Grey Electronaut

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