Tesla Level 2 Charger Teardown

The U.S. Department of Energy says 80 percent of EV charging occurs at home. However, as EV owners increase, many apartment dwellers or people parking on the street use public chargers or chargers at their workplaces to charge their EVs.

 

Image used courtesy of ChargePoint 

 

One of the unique advantages of an electric vehicle (EV) is the ability to charge an EV overnight at home, meaning that, essentially, an EV owner can leave each day with a full “tank” of energy and, under normal circumstances, won’t need to use public charging stations to replace the electrical energy in their vehicle’s battery. 

 

Tesla Wall Connector. Image used courtesy of Tesla 

 

Teardown: Tesla Level 2 Chargers

Michigan-based Munro & Associates has made part of its mission to tear down automotive products, examining innovations and providing benchmarks for technology-based customers. Munro focuses on EVs via videos that teardown Level 2 chargers, describing how they are made and the advantages and innovations they contain. 

The series started with the Tesla Level 2 Wall Connector as a benchmark and compared other charger units with the technology provided in the Tesla unit. 

 

Video used courtesy of Munro & Associates 

 

The Munro team found the Tesla Level 2 device to be well-engineered. According to the video report, it was designed by engineers who were able to make it more compact and easier to manufacture thanks to bespoke circuitry, housings, and a clever wall-mounting system. This is in contrast to other Level 2 devices which sometimes use off-the-shelf components or more generally available generic containers to house their products. 

 

Unexpected Charging Danger

The Munro series on Level 2 chargers only examines the design and components that make up the devices and does not provide any testing of the equipment or its claims. Munro has, however, discovered a potentially dangerous possibility that can occur if a Level 2 charger is attached to 240-voltage through the electrical plug usually used for a dryer or electric stove rather than hard-wired into the household wiring. 

They found that many of the NEMA (National Electrical Manufacturers Association) 240-volt plugs rated for 50 amps are designed for a short-duty cycle at this current rating. This is fine for a dryer that runs for 30 minutes to an hour three or four times a week but can be catastrophic when used at the much longer cycle time an EV requires – as much as 8 hours of continuous charging at full current for 8 hours or more. Because NEMA connectors range from as little as $15 to more than $120, and no markings indicate which are best for continuous duty, even installations done by licensed electricians could overheat and catch fire during the charging process. 

The best answer is hard-wiring the Level 2 charger directly into the house current and avoiding using the NEMA connector. If this isn’t possible, the best NEMA connector with high-temperature resistant Bakelite rather than less resistant plastic materials should be used. 

 

Sorting EV Charging Levels

There are three levels of EV charging:

• Level 1 charging is the slowest and uses a standard household outlet. With just 1-2 kilowatts (kW) of power, it can take up to 24 hours to fully charge an electric vehicle using Level 1 charging. An 8-hour charge using Level 1 provides about 36-40 miles of EV range.

• Level 2 uses a 240-volt outlet like what is used for an electric dryer or stove. With between 3 and 20 kW, it can take 4-8 hours to fully charge an electric vehicle using Level 2. An 8-hour charge using Level 2 can provide as much as 180 miles of travel.

• Level 3 charging is the fastest and uses direct current (DC) to charge an electric vehicle's traction battery in minutes. Level 3 chargers with a capability of between 50 and 400 kW are often called DC fast chargers (DCFC) or superchargers. Level 3 can provide over 200 miles of range in 20-30 minutes.

Level 1 and 2 chargers are typically used at home or work. Level 3 chargers are typically found in public places like shopping malls, parking garages, and rest stops.

 

Electric Vehicle Service Equipment

Technically speaking, Level 1 and 2 aren’t really battery chargers – they are more properly called electric vehicle service equipment (EVSE). That’s because they provide electrical power to the EV’s onboard charger, which converts household AC to DC at the proper voltage to recharge the vehicle’s traction battery. However, the distinction is rarely made, and the industry typically refers to Level 1 and Level 2 equipment as EV chargers. 

Installing a Level 1 charger is as easy as plugging it into a household 120-volt wall socket and plugging the connector into the EV’s charging port. A home’s wiring and circuit breakers will easily handle the low current draw. 

Connecting a Level 2 charger is more complicated as it must be connected to a 240-volt power source and will be hardwired directly into the home's electrical system.