How to charge your electric car from 120 volt power outlets

With careful preparation you can charge an electric car at full speed from 120 volt electrical outlets, making use of ubiquitous the electricity supply, but only if done correctly.

What if the state of charge on your electric car is running low, and the Recargo or Plug Share app's do not show a nearby charging station? Are you out of luck and your only choice is to call a tow company and paying a large towing fee? Electricity is everywhere, but the powers-that-be decided electric cars must be charged through plugs designed for that purpose. The U.S. the ubiquitous outlet offers 120 volts through a plug that's not certified for electric cars, and in any case the low charge rate (1-1.5 kilowatts) on 120 volt outlets means an ultra-long recharge time. Some DIY types are taking matters into their own hands and developing adapters to recharge electric cars, at reasonable speed, through any 120 volt power outlet. But some care must be taken to do this successfully.

The first item to understand is the EVSE, which means Electric Vehicle Service Equipment. The EVSE is the technical name for the "charging station" and is the approved method for charging an electric car. It includes a number of safety features, such as an interlock preventing the car from driving if it is plugged into an EVSE. Obviously a "drive off" from a charging station could be dangerous, and expensive. You'll notice that electric cars do not have a normal power outlet, but instead have a J1772 charging port.

One of the hindrances to electric vehicle adoption is the rate at which EVSE's are being installed around the country. Charging stations aren't always where we need them to be, and some cities are seeing a low rate of EVSE installation. This creates a condition in which it's extremely desirable to work out a method for using normal 120 volt outlets to charge electric cars. This way electric vehicle owners can still charge their cars, even if their local EVSE network is insufficient.

Every electric car comes with a portable EVSE meant to plug into 120 volt outlets. These adapters support a modest charge rate of at most 12 amps, sometimes less. The 12 amp rate corresponds to a 1.4 kilowatt charge rate, which in turn is why charging at 120 volts could take as much as 20 hours for a full recharge. Still, if this is your only choice to charge your car it's what you'll do.

An 120 volt EVSE offers what's called "Level 1 charging". Level 2 charging is what's available at regular EVSE's.

Some electric car owners with short commutes find they can get along without a level 2 EVSE at home, and simply rely on the 120 volt EVSE and a normal power outlet in their garage.

Some of the level 1 120 volt EVSE's can be upgraded (primarily, the one which comes with the Nissan Leaf) to support either 120 volts or 240 volts, and bump the maximum amperage to 16 amps. The 240 volts 16 amps, charge rate is the same as the level 2 EVSE's meaning that one can feasibly skip buying a normal EVSE, get the 120 volt EVSE upgraded to 240 volts, and enjoy the same charge rate. The upgrade service is offered through EVSEupgrade.com. The warranty on your car remains intact, but the upgrade does, of course, void the warranty on the 120 volt EVSE.

Another option is that some of the level 2 EVSE's are small enough to carry with you, and can be plugged into regular 240 volt outlets. For example the Leviton EVB22-3PM has a NEMA 6-20P plug supporting 16 amp charge rates, and is luggably small enough to carry around.

This is great if you have a 240 volt outlet available, but in the U.S. these outlets are rare. This is where the Quick220 gizmo comes into play, as well as some tricky details on the design of the electrical system. Every house in the U.S. has 240 volt service, but rarely has 240 volt outlets. A 240 volt outlet is powered by two 120 volt hot wires that are 180 degrees out of phase. What this means is that by connecting two 120 volt outlets together in the right way, you'll have a 240 volt outlet, but only if done correctly by finding two outlets which are on opposite phases. Do it incorrectly and the results will be messy. The Quick220 gizmo does it correctly. Alternatively, schematics are available in some corners of the Internet to build your own.

The next item to be aware of is the ratings on power outlets, and the quality of some power outlets, especially older ones. Basically, not all electrical circuits are equal, and some power outlets will fail when used to run a high load for many hours at a time. In March, GM started replacing the 120 volt EVSE's partly because of this issue. Some questions to ask are: a) what is the rating on the circuit breaker, b) what is the rating on the power outlet, c) what is the rating of any extension cords being used, d) what is the rating / gauge of the wiring in the walls, e) are there other gizmos plugged into the same circuit?

The non-upgraded 120 volt EVSE's should work well on pretty much any 120 volt electrical outlet, because the 12 amps or less charge rate is much less than the typical 15 amp circuit breaker. But what if the circuit you plug into has old or thin wires? What if the outlet itself is old and corroded? What if there are other devices, like a refrigerator, on the same circuit? The safest result is if the circuit breaker trips, but thin wiring carrying high current might heat, which could have disastrous results.

Likewise you may have an old extension cord lying around, but is that cord rated to handle the current to charge your car? It's best to look for the heaviest duty extension cord you can find, preferably one using 10 gauge wires.

With care one can use the right adapters to enable full power electric car charging even if no level 2 EVSE is available. But as we've seen, one must do this carefully. ALWAYS make sure you plug your electric car into an outlet you know is rated to handle the high current of charging. Where possible, use a real properly installed level 2 EVSE, because it'll be safer and more straight-forward.