Last year and this year see a veritable onslaught of low-volume German plug-in hybrids, both sedans and SUVs.

BMW and Mercedes-Benz have each said they'll offer plug-in hybrid versions of all their high-volume vehicles by 2020.

Those include the Mercedes-Benz S-Class large sedan, GLE-Class SUV (nee ML-Class), and C-Class sedan; for BMW, the first is the X5 xDrive 40e SUV that competes directly against the GLE.

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They will be followed by a plug-in hybrid version of the new 2017 E-Class just introduced last week at the Detroit Auto Show.

But virtually all of those models have electric ranges of no more than 14 to 20 miles, as does the Audi A3 e-Tron compact hatchback that went on sale last month.

Hope is at hand, however, or will be within a couple of years: Mercedes, for one, is planning to boost battery size to give its plug-in hybrids longer range, likely starting in 2018 or so.

2017 Mercedes-Benz E-Class (E350e plug-in hybrid)

2017 Mercedes-Benz E-Class (E350e plug-in hybrid)

That news comes from an interview with Thomas Weber, product chief for Mercedes, published yesterday on the Australian automotive site Motoring.

Weber says that Mercedes will have launched 10 separate plug-in hybrid models by the end of 2017, but that's not the end of the story.

“The next-generation vehicle will overcome the 30-km to 50-km hurdle," he told Motoring, "and then the next generation after that will be 80 to 100 km when they run as pure electric cars.”

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A range of 30 to 50 kilometers (19 to 31 miles) would be a noticeable boost on today's ranges, but likely not enough to ensure running a majority of miles on electric power.

That will come in the second generation after the current models, when 80 to 100 km (50 to 62 miles) would get all models into the range of the current 2016 Chevrolet Volt.

As GM often mentions, nine out of every 10 trips in the new Volt can be done exclusively on battery power recharged from the grid.

2016 Mercedes-Benz S550e Plug-In Hybrid

2016 Mercedes-Benz S550e Plug-In Hybrid

it's worth noting that BMW has already previewed its system to get to that second level, known as Power eDrive.

The system uses a single electric motor for lower-speed travel around town, along with a battery pack large enough to permit Volt-like levels of electric usage.

And given the tendency of German carmakers to follow each other's leads, you can likely expect the same from Audi.

MORE: 2016 Mercedes-Benz C350e Plug-In Hybrid: First Drive

BMW already has its first generation of all-electric cars in the market, while Audi and Mercedes will both launch 200-mile or better electric cars around 2018 or 2019.

But the big question--unanswered by Weber--is when that second generation of Mercedes plug-in hybrids will arrive.

if you assume two- or three-year improvements in lithium-ion cell energy density, that likely won't be until the 2018 or 2019 model years.


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