Hi; noluddite; Merc are working on electric units which I think are due out 2010 or 2011; they are based on the current A class and B Class; autocar it an item on them.
It has been well reported that the A Class chassis is being used for the first unit that is to be released; bearing in mind that the A Class has a sandwich chassis that was designed 10 or more years ago....the sandwich is for BATTERIES....that's right.....they designed it all in back then......clever Merc; come on fella catch up!
You will find that GM (if memory) serves started on the Volt about 10 years ago....as a side note; also Ford had an EV Ranger in the USA which people really linked; if you type electric ranger or ev ranger into google you should find a link to Wiki for your homework!
Further you have then the Smart Car electric......so I would say Merc are way ahead of the curve....then also they acquired 10% of Tesla Motors the other month or so.....I think you can rest assured Merc have thought it through!! I cannot wait for this model and I guess it is the first of many with this one being an expression of capability.