From the first word that the North American version of the
I even have had people ask me if I could conduct specific tests with my car to confirm it can do what they need it to. The reason being is the 34hp REx engine can only deliver about 25kWs (although some reports say BMW upped it to 28kWs) of power. That is plenty of power for nearly all normal driving needs, but not enough for continued high speed or long upgrade driving. The problem then arises if you continue to consume more energy than the REx can deliver.
This creates a problem when the driver needs to drive for an extended period which demands an energy draw of more than 25kWs. The meager 6.5% battery reserve can quickly deplete in these conditions. When this happens, the car goes into a reduced power mode and can only maintain a speed of about 40mph. To make matter eve worse, the driver gets no warning and the car just slows down. This is not what you want happening to you when you are on a highway and cars are whizzing by you at 70mph. This is a real issue, and compounded by the problem that most BMW client advisers didn’t know how to communicate this to the customers and sold them the cars without informing them how to properly operate the vehicle in REx mode. I’ve had people contact me that were completely unaware of how the range extender worked and said they were told by their client adviser that “the car can do anything in range extender mode as it can in all electric mode, it just doesn’t have quite as much power.” That isn’t true, and many early i3 REx customers were disappointed when they found out they couldn’t drive up that mountain to their summer home, for example. In fact,
All that said, I now have over 10,000 miles on my i3 REx and not once have I ever gone into reduced power mode, and I’ve actually tried to make it happen! The “problem” I’m having is the highways are relatively flat here in New Jersey and the REx can basically handle anything I give it. The times I have tried to make it happen the flow of traffic wasn’t fast enough for me to maintain a speed of over 75mph for a long enough period. 75 mph on relatively flat ground seems to be the upper limit the REx can handle for continued driving. There is plenty of energy to go up and down the hills I routinely drive over, and also to have short bursts of power well past 80 mph for passing if needed in REx mode, so for me the car works perfectly and I really don’t need a modification. However my friends in California and other areas of the country that have long, steep inclines to negotiate disagree, and want to see some kind of modification to allow the range extender to turn on at a higher state of charge so the vehicle has a larger electric buffer. In fact, there will soon be a two-part post here by an i3 Rex owner in California that has been obsessing a bit over this very topic. (well, I call it obsessing, he calls it studying – I’ll let you be the judge when you read his post next week!)
So now that we understand the problem, what is the solution. Should BMW simply give up the value of the BEVx designation and allow the driver to initiate Hold Mode as the European i3 REx owners can? That isn’t happening as far as I can tell. What I do believe is going to happen? Well for starters there will be software updates that include better indicators that the car may be headed to reduced power mode if you don’t take action to alleviate it. Perhaps by slowing down 5-10 mph you can completely avoid having a problem at all. I also expect there will be a better state of charge display so the driver has more accurate display of how much power they have left. I would also love if BMW could add a display that would show the actual power draw you are using, so the driver can see if they are drawing more energy than the REx is producing. That would be an awesome tool for the driver to use in these situations and I do hope the BMW engineers consider adding it.. However I’m saving the best for last. It is my belief that BMW is working on an update that will indeed allow the range extender to turn on much earlier than the 6.5% threshold if the car determines you will need the extra power. This will work with the navigation system which accounts for topography. Once a destination is entered, the car will determine how early the REx will need to be turned on so it avoids reduced power while climbing an upgrade at the end of the journey.