BMW is hedging its bets with the i3 electric city car.

You can buy it not only as a pure electric vehicle, but also as a range-extended electric car. And if the extra price and curiously stunted extra range hadn't put you off so far, perhaps reviews of the range-extended model might dissuade you.

First impressions from The Telegraph (via Transport Evolved) are positive on some counts, not so happy on others--and it's largely down to that range-extending component and the compromises it brings to an otherwise impressive package.

The 2014 BMW i3 remains impressive overall. Just as we discovered in our first-drive review, the i3 is a talented little car with cutting-edge styling, largely excellent interior design and some impressive technology. It drives well too, if not in quite the same way as more traditional BMWs.

Still, some people may need that extra 80 miles or so of range the range-extending model supplies.

This is where the car falls down--as The Telegraph discovered.

First, a 70-mile journey (no problem for the range-extender, of course) turned out to use the car's full 65 miles of electric range. Some of that might have been down to the weather, and the route between London and their Folkestone destination isn't the flattest of trips either. All this can eat into range.

However, it's apparently little better in range-extending mode. The car's fuel tank is tiny--around 2.3 gallons, limited to keep California's regulatory bodies happy.

At the UK motorway speed limit of 70 mph, it appeared to offer added range of only 40 to 50 miles--for a combined range of no more than 115 total miles on that particular test.

Push it longer--to the point where battery capacity really declines--and performance starts to suffer in an alarming way.

According to the reviewer, the car slowed to just 44 mph or so heading up an incline, proving an impediment to even heavy commercial trucks that are limited to 56 mph in the UK.

Once it return to flat roads, the car crept slowly back up to motorway speeds.

2014 BMW i3 Electric Car: Connectivity, Navigation Highlights

2014 BMW i3 Electric Car: Connectivity, Navigation Highlights

The reason is simple, as BMW explains. When charge in the battery pack falls too low, the car prioritizes boosting the battery during range-extended mode, rather than maintaining performance.

But that may be little consolation if you're attempting a longer journey.

What the journalist should have done, says BMW, is engage the range-extender when there's still 30 to 40 percent of the charge left in the battery. That way, it's always kept topped-up and consistent performance is maintained for longer.

That's all very well, but what you end up with is a zero-emission electric car whose electric range is compromised by the need to use the range extender much earlier if the i3's performance is to stay consistent.

And that's a pity--because the i3 is still described as "a delight" to drive.

The moral of the story: Unless you're convinced you'll need the modest extra range of the i3 REx, the regular, all-electric car may be the better (and cheaper) choice.

And if you do use the range extender, make very sure you understand how it works--and under what circumstances it will limit road speed.


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