REX Reduced Power Mode

BMW i3 Forum

Help Support BMW i3 Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

shellzj

Member
Joined
Dec 12, 2017
Messages
7
Yesterday I took my 2017 i3 REX 94ah for an impromptu road trip from Houston to Austin, Texas. The drive is about 160 miles one way and includes both interstate and highways with speed limits as high as 75 mph. The highway becomes very hilly about 60 miles south of Austin, which is also when my battery was depleted and the REX kicked in.

The i3 could not keep up. With battery power, I was going about 85mph. Going up a hill, this speed bled off to as low as 55mph. It was just me in the car along with negligible belongings. It was about 60 degrees outside, but I had the climate control turned off.

Coming back with a full charge, I was able to get past the hilly highways on battery. The REX kicked on Interstate 10, which was mostly flat outside of Houston. Whereas I was normally going about 80mph on battery, the REX only managed about 70 to 75mph.

This is my second i3 but first REX. I had a 2015 BEV before taking delivery of the REX in October. I had seen some brief mentions about reduced power mode before but assumed it was under rare, extreme circumstances.

My cursory research says that this reduced power mode could be US-specific, as the REX only kicks on at 5% state of charge. And that it is possible to have the dealer have the REX kick on earlier.

Clearly I will not be taking the i3 on another road trip anytime soon. But this trip came up so suddenly my local BMW dealer didn't have any loaners, and the local car rental place was out of cars too.

It's a rare but realistic situation. I still love the car (it was surprisingly enjoyable to drive on the twisty roads outside Austin before the power loss) but wish I had been made more aware of this significant limitation. Although, if I had been made more aware, I'm not sure it would've altered my buying decision significantly since a) my lease payments are only $1 more versus the 2015 REX and b) there were no BEVs available.

Any advice? Has anybody had the dealer program the REX to turn on earlier?
 
It's my understanding the dealer will not do anything about it. You need to take things into your own hands and code it or find a non dealer to do the coding for you. You can increase it higher then the 6%, or just have the hold mode enabled so you can decide when you need to use the REx like non-us i3's do. In the non-US versions anytime under 75% you can tell it to maintain that level of charge and have all the power you need for hills and such. When you don't need it you can let it run down to the 6% and get more electric range with out using gas.
 
shellzj said:
My cursory research says that this reduced power mode could be US-specific, as the REX only kicks on at 5% state of charge. And that it is possible to have the dealer have the REX kick on earlier.
Minor nit: your i3 has a 94 Ah battery pack, not 90 Ah. 2014-2016 i3's have 60 Ah battery packs which was also an option on 2017 models.

BMW dealers won't change the settings on a REx to allow the driver to start the REx engine manually whenever the battery pack's charge level is <75% which is standard behavior in all markets in the world except North America. But you can change these settings yourself if you have an iPhone or Android phone.

• Download the BimmerCode smartphone app from your phone's app store.
• Pay ~$27 to its developer in an in-app purchase to allow the app to save the changes you make.
• Buy a Vgate iCar 2 or 3 OBD-WiFi dongle (~$12-$22 from Amazon, any color).
• Follow these instructions. Since these instructions were written, an Android version of BimmerCode has been released should you have an Android phone.

You would enable REx Hold Mode to do what you want. There are many other changes unrelated to the REx operation that many of us have made to make driving an i3 more convenient.

Dealer-installed system software updates can return the settings to their default values, but with BimmerCode, you could restore the settings that you prefer at no additional cost.
 
Thanks, I thought it looked weird when I typed 90ah - anyhow, I'm glad BMW is switching to the industry standard of quoting in kWh instead.

I just downloaded the app and ordered a vgate. Maybe I will try another road trip in a couple of weeks...

But I have to admit, I can see why the 2016 class-action law suit came about. I was thinking about how some states have minimum speed limits, and I wasn't able to keep up. On the way back, I was content to follow a Chevy Aveo because I couldn't get the power to pass...
 
For a car designed as a city/commuter car...extended trips at 85mph were not in the design parameters otherwise, they would have used both a larger generator (REx) and gas tank. But, then the car would not be as efficient as it is for what it was designed for. If your trip requires the use of the REx, rather than it being a backup in case it's close, is, IMHO, using the wrong tool for the job. Use a pair of pliers when a wrench is better, then complain that the pliers don't work perfectly all of the time...give me a break.

What I do fault BMW for is educating the new user on exactly what and how and when this protection mode works. FWIW, even if you can tell the REx to start earlier, if you don't stop to recharge and refuel on a long trip, you'll run into the same problem. About 70mph on the level is about the best the REx can hold the battery charge...faster or throw in a long grade, depending on how long and when it might recover going down later, you could still end up with the same problem.

From what I've read, the original designers did not want to include the REx, but marketing felt people would feel more comfortable, and thus sales would increase, if it was offered. There's only so much you can do and keep the weight down and the efficiency up, which was the primary goal.

Yes, I know there will be pushback on this opinion, so no need to respond...it is an opinion.
 
I think your opinion is completely valid, and I mostly agree.

The i3 is a fantastic city car, and had I a need for a single car that could do it all - including regular 150+ mile road trips - I would've stuck with a Volt. But as it is, I drive less than 5k miles a year, and this trip was spontaneous and happens about 2x a year. In October, the leases on both my cars expired (i3 and ELR). I only re-upped on the i3 since I thought it was wasteful to have a second car for the 2x a year I might need more range, plus my dealer participates in flexible mobility so as long as they have 24 hours notice.

And I also agree that the i3 would be better offered as a battery only vehicle. I think the blame does lie with the marketing department and the folks at CARB for giving us the underpowered REX.

Imagine the REX marketing conundrum - the sales guy says, "this car will take you wherever gas is available" but the engineering department puts a red sticker on the window that says, "max sustained speed is 70mph on flat terrain with 0 headwind at 70 degrees."

I'd love to see more batteries fill the space used by the REX. I'm sure there are other restrictions like crash-worthiness, but imagine if you could put more batteries in the scooter engine cavity and in the frunk - wouldn't that get the i3 easily pass the 200 mile range?

More range and better charging infrastructure - the old EV dreamer's refrain.

However my bigger concern at the moment is the bifurcation of the US ev market between CARB and non-CARB states. A big reason I went with the i3 over a Bolt was that Chevy doesn't stock and incentivize the Bolt well in Texas. But I understand that the financial case isn't there for non-CARB states.
 
Just think what will happen when CA, if it passes, prohibits ANY new ICE sales in their state after the proposed 2040 timeframe! And, what are the US manufacturers that want to sell cars overseas going to have to do if they decide to take advantage of the laxer emissions standards being talked about by our President and EPA, when none of them would be able to be sold overseas. How is having to design for multiple markets really going to make us great again? There was talk, but certainly not action, on trying to set one standard, or at least allow one country's vehicles to be sold in anothers, as long as it met the local requirements for where it was made. This made some sense when the rules started to merge on both safety and emissions...but, that never came to pass, and now, probably never will. While some vehicles sold elsewhere would never appeal to a typical US buyer, there are some that would, but having to make a special version for the USA just makes it uneconomical. That part would have gone away if the standards continued to merge, as there would not have to be changes made to certify it for sale outside of their normal market.

The CA market is huge in comparison to any other single state in the union.

Way back when emissions requirements first became a thing, many of the manufacturers, at least US based ones, made two completely different emissions systems...one for sale in CA, then another for the rest of the country...it was a major pain. China is the single largest purchaser of new vehicles in the world...but, ICE vehicles and efficiency doesn't matter, at least if you listen to our administration. No need for the kick start for EV's, either...trash the tax credit.

Sorry, this is devolving into political issues, and I should stop.
 
I had my 2014 REX re-coded by DVD in Motion so I can manually kick on the REX at 75% (plus now I get AM radio too). Anytime I make a long trip on the interstate, I fire up the REX at 50% and drive 75 MPH max. The REX then can charge the battery even if the battery level drops 5-10% due to hills, the REX will stay on until the 50% SOC is achieved at 75 MPH. Once I get back into city driving then I'll turn off the REX and go back to BEV mode. BTW, the REX gets about 45 MPG so stopping every hour or so for a 5-minute pit stop is recommended. The drive from Houston to Austin is then easy-peasy
 
Once the REx is enabled at 75%, continue to drive at any speed. Speeds above 70 mph with the REx will eventually drain both the battery and the fuel tank:
  • gas out - refuel or the battery will quickly drain at high speeds
  • battery out - continue at 70 mph until out of gas (not recommended)
Monitor the gas level and refuel frequently. My 2014 BMW i3-REx experiments suggest that at 75 mph the battery will lose ~25% with each tank or 3 tanks. The problem is refueling means slowing down to reach a gas station, refueling, and accelerating back to highway speed. This impacts block-to-block speed.

If you have dynamic cruise control, follow a high-balling truck at 70 mph. Each tank will give about 70-75 miles easily. One refueling will easily cover 150 miles.

BTW, there are several alternatives to the Volt. But reviewing requirements is best handed in another thread. We also have a 2017 Prius Prime and it has a gas range greater than 600 miles and comes with dynamic cruise control.

Bob Wilson
 
Back
Top