There are still many unanswered questions about the i3. What will the EPA range rating be? How will is fare in NHTSA and IICA crash tests, will it cost more to repair, and so on. However there is one particular feature of the i3 that continues to dominate the discussion boards and forums: What can and can't you do with the REx?
Back in June before the i3 was officially introduced, I did a blog post on this very topic which turned out to be very popular. In fact, it's one of my top viewed posts and has been viewed over 5,000 times so far. We now know a few more details since then so I thought it was a good time to give an update here. While I have driven in REx i3's, unfortunately I haven't had the chance to thoroughly test on while it was in range extender mode. That wasn't a coincidence. BMW has still be fine tuning the software for the REx and hasn't allowed the press access to them for complete testing. However, somehow over in the UK The Telegraph got hold of one and was able to take to for a long drive and use the range extender. Overall the review was pretty favorable and the author gave the i3 four out of five stars. However that's not the whole story. The real "story" within this story is that the author reported this about the range extender and it's caused a but of a stir:
"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. Still, it was impressive how, even when it says it’s flat, the car maintains enough battery power to give an instant shove of torque. Only if you really run it down, which you’ll have to try pretty hard to do (or so I’d been told), would you compromise the performance. Which is what happened next.
I’d just come through a heavy but localised rain storm on the M20 when the i3 started to slow. It was a gradual process, from motorway cruising speed all the way down to 44mph. By this time I was travelling up a slight incline and had effectively become a slow-moving obstacle. Lorries were catching me with quite frankly terrifying closing speeds. It was three or four minutes - which was long enough to make me consider pulling over - before the i3 recovered; just as slowly as it had lost speed, so it crept up. “It’s not a limp-home mode as such,” a BMW spokesman later told me, “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.” Rather than damage the battery by running it completely flat, the i3 had restricted our performance."
This Telegraph video above doesn't mention the difficulty they experienced with the car slowing down at all even though they show it driving along on the M20 while it was raining like they printed version said. That's strange to me since the article seemed to make a big deal out of it. I would have like to have seen video of the car during the explained "slow down" event.
|The i3 REx Engine|
|i3 Product manager Oliver Walter|
|Of course a robust network of DC quick chargers like the one pictured here would render the range extender irrelevant. But are they coming?|