2014 Mercedes-Benz B-Class Electric Drive
  • 2014 Mercedes-Benz B-Class Electric Drive
  • 2014 Mercedes-Benz B-Class Electric Drive

  • 2014 Mercedes-Benz B-Class Electric Drive
  • 2014 Mercedes-Benz B-Class Electric Drive

  • 2014 Mercedes-Benz B-Class Electric Drive
  • 2014 Mercedes-Benz B-Class Electric Drive

  • 2014 Mercedes-Benz B-Class Electric Drive
  • 2014 Mercedes-Benz B-Class Electric Drive

  • 2014 Mercedes-Benz B-Class Electric Drive
  • 2014 Mercedes-Benz B-Class Electric Drive

  • 2014 Mercedes-Benz B-Class Electric Drive
  • 2014 Mercedes-Benz B-Class Electric Drive

  • 2014 Mercedes-Benz B-Class Electric Drive
  • 2014 Mercedes-Benz B-Class Electric Drive

  • 2014 Mercedes-Benz B-Class Electric Drive
  • 2014 Mercedes-Benz B-Class Electric Drive

  • 2014 Mercedes-Benz B-Class Electric Drive
  • 2014 Mercedes-Benz B-Class Electric Drive

  • 2014 Mercedes-Benz B-Class Electric Drive
  • 2014 Mercedes-Benz B-Class Electric Drive

  • 2014 Mercedes-Benz B-Class Electric Drive
  • 2014 Mercedes-Benz B-Class Electric Drive

There was something unexpected hiding in the new configurator for the 2014 Mercedes-Benz B-Class Electric Drive: a $600 "Temporary range extender." Since we've never heard of such a thing, we had to click through for more.

The official explanation runs like this:

A suite of options to further increase your driving range includes added insulation of the doors and roof for to increase climate-control efficiency, along with an electrically heated windshield and a range-extending charge function. By pressing a button on the console prior to charging, the maximum charge level for battery will increased for the next charge cycle. The higher-capacity charge can provide up to 17 additional miles of range.

The passive features that increase range should be standard in all models, we think. But we were more curious about the battery charge situation. How do you increase a maximum? And is it a good idea to do so? The configurator includes this disclaimer, after all:

Range extender should only be used on a limited basis, and could shorten battery life if used excessively.

How much is excessive? We investigate below.

Mercedes-Benz B-Class ED Configurator

The B-Class ED has, according to the specs, a 28-kWh battery.

First, let's understand what this "temporary range extender" is all about. The B-Class ED has, according to the specs, a 28-kWh battery. But Terry Wei, from the Mercedes-Benz USA product and technology communications department, confirmed to AutoblogGreen that the B-Class ED is actually hiding a 36-kWh battery, but the automaker is calling it a 28-kWh battery because that's how much energy capacity is used in day-to-day use. Most automakers publicly claim the actual capacity and then admit they use a percentage of it. The Chevy Volt, for example, has a 16.5-kWh battery pack, but a "full charge" only fills up around 65 percent of that.

In the B-Class ED, the 28 kWh of useable energy provides an EPA-certified 87 miles of range. But, since there are eight kWh of reserve, the temporary range extender (we think of it as a software update accessed by a button) can access some of that and offer the aforementioned 17 miles. Now that we know what we're dealing with, this reminds us of an evolved version of the "remote wireless charging" feature that was touted in the Reva EV.

Wei said that the reason the feature is optional is because Mercedes doesn't think most people will need it. Eighty-seven miles is plenty for your average EV driver, but when you want to have 100+ in the tank, you can. It will take an extra 1.5 to two hours to charge to the new "full" on an EVSE with between 24-40 amps, Wei said, adding that, "Basically what you are doing is using, early in life, any excess capacity in the battery," so the efficacy of the temporary range extender may change over time. For all these reasons and more (the EPA tests EV range using default settings, for example) the car's official range will remain at 87 miles.

Now, is this a good idea? Apparently, yes. The "limited basis" mentioned in the disclaimer might even be more than you think. "We don't recommend that folks do this all the time," Wei said, "and we can't really make a suggestion as to how often." But it sounds like using this feature pretty regularly, even once a week, will not be all that damaging to the battery pack. So, in our mind, if you're already paying $41,450 for the B-Class ED, then another $600 for some extra range when you need it seems like a easy addition to the options list.

Head on over to the configurator to see for yourself. The range extender is in the Performance & Safety section.


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  • 29 Comments
      Phlegming Liberal
      • 8 Months Ago
      I don't get 10.5kw out of my Volt, so it's less than 65%, however it is enough to get me 44 miles/charge.
      Koenigsegg
      • 8 Months Ago
      Smart ED over this
      2 wheeled menace
      • 8 Months Ago
      That's kind of an odd way of setting things up. But by running a ~77% state of charge window in the battery, the battery will last a hell of a long time. I know a few people in the ebike community that have stretched a 300 cycle chemistry to 600 cycles by running an 80% state of charge window. Running a very conservative state of charge window does tend to benefit the majority of batteries! One great example is the Prius's NiMH pack, which runs at a ~50% SOC window but lasts easily ~30,000-100,000 cycles before it poops out. But... how are they only getting 87 miles of range out of 28kw-hrs? this car could certainly be more efficient per watt, considering it's size. Either battery sag + heat due to using a low discharge, high energy capacity battery, poor aero, using a substandard motor, or some combination of these factors are probably to blame. I think Mercedes can definitely do better, but this is a good early attempt..
      Greg
      • 8 Months Ago
      Seriously? I thought it was common knowledge that charging/discharging these batteries all the way to their capacity shortened their life. Other EVs have this same feature--you can 'overfill' them if you need that extra mileage, but in doing so, you risk harming the battery; thus, by default it stays in the zone of greatest battery durability.
      Collin
      • 8 Months Ago
      I would recommend never shortening Electric Drive to ED. Reminds me of Bob Dole in the old Viagra Commercials.
      BipDBo
      • 8 Months Ago
      This is a great deal considering you are buying a Mercedes. Sure, you can compare it's price to a Leaf, but normally, you wouldn't dare compare a Nissan offering like a Versa with anything from Mercedes. You wouldn't even dare compare a Cruze to a C-class. And this is far superior to the Leaf going deeper than the hood emblem. It has more power, more range, nier interior, and they have obviously done more work to protect the batter from age and degradation, likely giving the car double the useful lifespan compared to a Leaf. This is almost Mercedes cheapest offering. The C-class MSRP starts at $35,800. If you calculate total cost to own and rebates, it's the cheapest by far.
        Joey
        • 8 Months Ago
        @BipDBo
        CLA is cheapest Mercedes at $29K.
      James
      • 8 Months Ago
      No need to get all scientific and theoretical on us. It is exactly the same thing Tesla has. Makes sense because it is a Tesla supplied battery pack. What is the big deal?
        MTN RANGER
        • 8 Months Ago
        @James
        I think it is kind of sneaky of Mercedes to charge $600 just to do a 100% versus 80% charge. I know they are adding so-called enhancements like insulation and heated windshield, but that still seems overpriced.
          Greg
          • 8 Months Ago
          @MTN RANGER
          They are a German car company. All their options are overpriced.
      Exooc news
      • 8 Months Ago
      would take fast charging ability over this...
      mustang_sallad
      • 8 Months Ago
      They probably based the $600 on the increased cost in warranty claims due to the select few cases that use this feature all the time and end up needing a battery replacement.
      EVSUPERHERO
      • 8 Months Ago
      Hello, I am happy to say I have 4 kinds of ED. Bob Dole ain't got nothing on me! Some people just don't care about ED and are happy limping to the gas station. We all know Anthony Wiener did not have ED.
      raktmn
      • 8 Months Ago
      This definitely makes for an interesting market test. It will be interesting to see when given the choice, what percent of buyers will spend approx. $35 bucks per mile for access to additional range. $600 for 17 miles? How about $1750 for 50 miles? $3500 for 100 miles more? The BMW i3 REx is right around that price for somewhere just under 100 additional miles of range on gas. $35 bucks a mile sounds like a pretty good deal to me. But the sales numbers will tell the rest of the story. So far it sounds like the BMW i3 is selling a lot of REx's, and $35 bucks a mile for additional range seems to be pretty cheap compared to the roughly $100 per mile price premium that the Tesla 85 carries over the 60kWh (correcting for the additional standard features and supercharger access).
      Winnie Jenkems
      • 8 Months Ago
      "The Mercedes-Benz B-Class Erectile Dysfunction" Yeah, don't even think about selling this here without coming up with a better name.
        Bernard
        • 8 Months Ago
        @Winnie Jenkems
        That's interesting because I would think this model would be the Mercedes least likely used to treat that disorder...
          Cavaron
          • 8 Months Ago
          @Bernard
          Hrhr, you made my day :) But I thought BMW customers have this kind of disorder much more often than MB customers ;)
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