Available with or without a range-extending engine, the 2014 BMW i3 has proven itself to be one of the most popular new cars of 2014, with strong sales around the world.
The all-electric i3, with an EPA-approved range of 81 miles per charge is currently the most efficient car on the market today, achieving a combined fuel economy rating of 124 MPGe. Its sibling, the BMW i3 REx, manages just 72 miles per charge, thanks to the additional weight of the gasoline tank and range-extending two-cylinder engine.
Unlike the i3, which requires recharging when its battery runs flat, the BMW i3 REx has been sold to appeal to those who suffer from range anxiety, with the promise that the small gasoline engine will provide enough range-extending capabilities to get you out of a sticky situation should you run flat.
But as we first covered last year and again a few months back, the BMW i3 REx — which like the all-electric i3 can be rapid charged from empty to 80 percent full when equipped with a Combo DC quick charging port — can suffer reduced performance when running in range-extended mode with an almost-empty battery pack.
So far, how the battery pack and car will behave when near a low battery has been a bit of a mystery, but a the folks over at InsideEVs have revealed, a leaked BMW training manual worksheet shows exactly when BMW i3 REx drivers will start to notice reduced performance.
What’s more, the site explains, many dealers don’t share this information with buyers, leading to confusion and misunderstood expectations of what the car can and cannot do.
In a moment, we’ll detail some of the salient points of this BMW-produced guide, but in the interests of clarity, we’re going to point out the problem of reduced power output is more of a problem among U.S. BMW i3 owners than it is anywhere else.
That’s because European owners can manually put their BMW i3 REx into gasoline range-extending mode long before their car’s battery pack is depleted, thus slowing down the drain from the battery pack and avoiding any performance problems. In order to comply with various emissions regulations (namely those in California,) U.S. market BMW i3 REx models can’t switch their gasoline engine on until 6.5 percent of the battery’s charge is left. What’s more, U.S. customers can’t put their cars into ‘hold’ mode either, where the battery pack is kept at a certain charge level for later in the trip.
This means that if you’re planning on driving a BMW i3 REx long distance beyond the range of the electric-only mode and you’re in the U.S., you should expect reduced performance at some point.
As the BMW training manual explains, the BMW i3 REx operates with full power in electric-only mode until the battery is 93.5 percent empty. Depending on conditions, that equates to as little as 45 miles in electric mode in cold, unfavourable weather to as much as 100 miles in warm, favourable weather. With those readings at extreme ends of the spectrum, BMW quotes more ‘usual’ readings of 50 miles in sub-zero temperatures, and 70 miles in ‘warmer’ conditions.
Regardless of how many miles you can drive in EV-only mode, BMW i3 REx’s two-cylinder range-extending 600cc engine will start to kick in when the on-board battery pack has reached 6.5 percent. At this stage, the gasoline engine will only switch on when extra power is needed, and doesn’t actually run continuously until the battery pack has been further depleted to just 3.5 percent of the battery pack’s state of charge.
From full until this point, BMW details, it’s possible to drive the car in full-power mode without suffering any performance loss.
At a state of charge below 1.9 percent, BMW notes that “Driving with restricted power and reduced speeds may be experienced (e.g. during hill climbs or high-speed driving.)”
When the battery pack’s state of charge drops below 1.5 percent full, the small blue bars in the BMW i3 REx’s power reduction display start to fade away, and power begins to be more thoroughly depleted. At a state of charge of less than 0.5 percent, the car works in full power reduction mode, using only power from the on-board generator.
On paper, the BMW i3 REx can drive up to 150 miles on a full, 1.9 gallon tank of gasoline and a full charge, As we’ve detailed above however, it’s clear that beyond 72 miles of travel, you’re likely to notice a performance degradation if you’re driving at high speed on hilly terrain on have a lead foot.
Does this make the BMW i3 REx a poor choice? No, but anyone considering the BMW i3 REx should accept that the range-extending engine isn’t any more suited to longer-distance, no-stop trips than a large Range Rover SUV is suited to life as a delivery vehicle in Manhattan.
You can do it, but it isn’t exactly the best vehicle for the task.
As BMW has said many times in the past, the BMW i3 REx’s gasoline range-extending engine isn’t meant to be a replacement for the on-board battery pack: it’s meant to help you get to the next charging station in an emergency. Given the number of problems that many charging networks around the globe have with reliability, that feature is a welcome one for many would-be electric car owners.
But if you’re looking for a car that can run in electric-only mode for most of the week and travel long-distance at the weekend without power restrictions on gasoline, you may want to look at other options like the Chevrolet Volt, Mistubishi Outlander PHEV, or Ford C-Max Energi instead.
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