As each automaker adds urgency to its electric-vehicle business plan and mentions solid-state battery technology as the future, remember this: Solid-state cells are already in use in vehicles, just about every day.
Where are they used? No, not a skunkworks in Sweden, or a closed loop in Japan. Public passenger buses in Wiesbaden, Germany, with the buses purchased as part of a state-backed environmental fund.
These Mercedes-Benz eCitaro buses are offered directly by Mercedes-Benz and have 441 kwh of solid-state LMP cells supplied by France’s Blue Solutions, part of Bolloré—and, seemingly, an evolution of the cells that Bolloré tested in car-sharing vehicles back in 2015.
Blue Solutions LMP solid-state tech
But these are not quite the automotive-grade solid-state cells expected around the middle of the decade—the ones that have the potential to offer more energy density, a reduced charging time, and improved safety. There are definitely some caveats—some that the owner of a personal EV might not be so willing to put up with.
The eCitaro solid-state as it is now really requires a charging depot and a fleet manager to oversee its persnickety demands. It needs to be charged all the way up to a 100% charge and maintained there, at which a balancing procedure takes place “to ensure an optimum performance of the battery,” noted Daimler Trucks’ spokesperson for bus products, Nada Filipovic, to Green Car Reports.
It’s also a chemistry that requires temperatures that, well, aren’t quite in the normal temperature range for vehicle batteries. According to Filipovic, the solid-state cells also need to be maintained at approximately 80 degrees Celsius (176 degrees Fahrenheit), but Mercedes-Benz says that it can be maintained there for three to five days.
VW Power Day - fast-charging for solid-state
To compare this to current automotive-grade lithium-ion cells, I’ve been told by a number of R&D officials that the ideal temperature for such cells is just above 20 degrees C, or about 70 degrees F.
So far, Mercedes-Benz Buses has delivered 40 of these eCitaro models with the solid-state cells, and so far so good. We look forward to a more extensive update from either Blue Solutions or Daimler Trucks—and, of course, to solid-state cells that don’t require such logistical hoops.