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Delta kicks off DOE-sponsored program to develop microgrid-capable solid state transformer-based 400 kW fast chargers for EVs; XFC

Delta, a global provider of power and thermal management solutions, has commenced work on a research program, with 50% cost-share by the US Department of Energy (DOE), to develop a solid-state transformer (SST)-based extreme fast EV charger (XFC) with industry-leading capacity up to 400 kW to provide capable EVs a 180-mile range with less than 10 minutes of charging.

The proposed XFC design is expected to offer grid-to-vehicle efficiency up to 96.5%—four times less weight and half the size of conventional DC fast EV chargers (DCFC), as well as a high voltage direct current (HVDC) port to utilize energy storage and renewable energy systems, minimizing demand on the power grid.

This initiative will be supported and led by a program development team consisting of industry experts based out of Delta’s automotive division, located in the greater Detroit area (Livonia, MI), and researchers from the Delta Power Electronics Laboratory (DPEL), located in North Carolina’s Research Triangle Park.

Delta’s partners for this 3-year, US$7-million project include General Motors LLC, DTE Energy, CPES Virginia Tech, NextEnergy, the Michigan Agency for Energy’s Energy Office and the City of Detroit’s Office of Sustainability.

The novel SST power cell topology directly utilizes medium-voltage alternating current (MVAC) at 4.8-kV or 13.2-kV, eliminating conventional line frequency transformer (LFT) technology, which converts low voltage alternating current to a direct current (DC) to charge the high voltage battery in an EV.

Combined with a new silicon carbide (SiC) MOSFET device, the proposed SST enables a 3.5% improvement in grid-to-vehicle efficiency to industry-leading levels up to 96.5%, a 50% reduction in equipment footprint, and four times less weight than today’s DCFC EV chargers.

Moreover, the 400 kW XFC prototype, which is expected to be ready in 2020, will boast a power level enabling ground-breaking 3C charging speed on tomorrow’s long-range EVs. With this technology, EV drivers will need close to 10 minutes to achieve an additional 50 percent of vehicle range on their vehicle. For example, a 360-mile EV could achieve a 180-mile range in approximately 10 minutes of charging.

Early data and results from the program will arm automotive manufacturers, technology providers, cities and utilities with a greater understanding of how fast-charging will impact demand response efforts within specific circuits. The project will also provide insight into how renewable generation can be integrated to avoid infrastructure strain on the power grid associated with the wide deployment of XFCs.



3 C charging... let's scratch a bit on the back of an envelope.

Suppose you go off on a trip in your 240 mile EV.  You drive 2.5 hours at 70 MPH (65 miles remaining) and take a rest break for 10 minutes while charging at 3 C.  In 10 minutes, the car picks up 120 miles of range for 185 miles total.  You then drive another 2 hours (140 miles) to your lunch break, leaving 45 miles in the battery at the stop.  A 30 minute lunch break tops off the battery to full.  Then you do this again in the afternoon, covering another 315 miles before dinner for a total of 630 miles.  A 30 minute dinner break brings the car back to full charge again, allowing 800 miles of travel with fairly safe margins even with a 240-mile car.

That pretty much gets rid of the case for the ICEV.


Sure, get rid of ICEV ... ruining the battery at the same time because charging with 3C rate will most definitely shorten the battery life.


One more thing: charging efficiency drops substantially at 3C ... well, but who cares.


Yes E-P. A 315+ miles extended range BEV could reduce trip charging from 3 to one (at mid day) and charging rate could be slowed to protect the batteries?


Harvey, you weren't paying attention.  My example was a 240-mile EV, roughly a Tesla Model 3.  3 C charging gives cross-country road trip capability to even such a limited car.

Steven F

"Harvey, you weren't paying attention. My example was a 240-mile EV, roughly a Tesla Model 3. 3 C charging gives cross-country road trip capability to even such a limited car."

Actually any tesla model can do this today. The tesla supper charger network allows this. And surprisingly it doesn't negatively affect battery life. Some tesla's are used as taxis and they daily use tesla supper chargers. These taxis have put on over 200,000 miles with only a 10% capacity loss.


The proposal was to use an extended range BEV or FCEV and charge/refill only once at mid-day during lunch instead of the 3 charges proposed.

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