Range Confidence: Charge Fast, Drive Far, with your Electric Car

By David Herron

Safely use Extension Cords when charging an electric car or electric motorcycle

Your electric vehicle was supposed to transport you around town and beyond. The problem is range and charging station availability. With enough public charging stations, electric cars can drive any distance. Unfortunately between the 80-120 mile range of most electric cars, and that insufficient public charging, we face serious limitations. But does that mean we must be limited to traveling a short distance from home?

Electricity is everywhere in these modern times. What's lacking is the charging connectors at charging stations that are required for charging.

If we only charge at home, we're limited to driving within a circle around our home. When we charge at public charging stations, our driving range is limited to areas with charging stations. Why should we allow either of these to limit where we can drive? Electricity is everywhere, why not access that electricity to drive anywhere?

Successfully electric car travel over long distances, at this time, means having the flexibility to use any power outlet you find, and the equipment to maximize the charging rate. You must develop the skills understand some simple rules for safely using (and maybe building) extension cords and adapter cables matching any power outlet.

The public charging network, and informal use of power outlets

Currently (2017) the public charging station network isn't enough to let us freely drive our electric vehicles anywhere we want. Most cities have public level 2 and even fast charging, but the inter-city charging network is weak. Even though electricity is everywhere, the electricity has to be adapted into a charging plug for recharging the car. The good news is we don't have to be limited to the public charging station network. There are plenty of high power electrical outlets available, and with the right equipment we can snag a 6 kiloWatt charging rate for a fairly reasonable charging time.

The car manufacturers provide a 120 volts 12 amps (1.2 kilowatts) line cord charger with each car. That unit is better than nothing, since you can always find a compatible power outlet.

The outlet shown to the right, a NEMA 14-50 outlet, is the primary objective for full-speed 6 kiloWatt electric vehicle charging away from both home and the public charging network. This, and other 240 volt 40 amp outlets, will let you charge at 6 kiloWatts continuous power. That's enough for 25 miles of range per hour of charging. (see Understanding charging rates and effective trip speed) Many RV parks have these power outlets, making them potential informal charging locations opening the door to driving into areas lacking public charging infrastructure.

Wait, isn't it dangerous to use an extension cord to charge a vehicle?

Is it safe to use extension cords and adapters to charge an electric car? Yes, with care. Can you charge an electric car from a dryer outlet? Yes, with care. The short answer is to use a good quality extension cord with thick wires and beefy plugs. In the lists below we show several choices for 120 volt 10 gauge extension cords that are safe for use with a line cord charger, and several 240 volt 40 amp extension cords safe for use with higher power charging stations. Further, a J1772 extension cord is completely safe due to cords and connectors built for the purpose.

WARNING: Vehicle manufacturers universally warn against using an extension cord to extend the reach of the supplied line-cord charger. Please, exercise caution in reading what is written here.

The general principles are:

Where does the heat come from in a substandard situation? A skinny cord, frayed wiring, bad power socket, acts like a "resistor" or "heating element". Sending too much current through a bad connection acts like a heater. Say your car is pulling 6 kilowatts, a 10% loss from a bad connection means 600 watts being dissipated as heat, or about the same as a typical hair dryer. That's a common cause of electrical fires.

Avoid violating Electrical codes Smart electricians and electrical engineers have spent decades cooperatively developing the electrical code. Their recommendations were won through hard work and the occasional electrical fire. It's easy to create adapters to connect a 240 volt 50 amp device to a receptacle rated for 120 volts 20 amps. That's obviously not going to work terribly well, because running 6+ kilowatts through a 120 volt 20 amp plug is going to cause a problem. The device for which you create such an adapter must accommodate dual voltages and automatically adjust its power.

Your fate is in your hands - this is for educational purposes. I am offering this for education, and you are responsible for your actions. Applied incorrectly this can cause electrocution or fire. Take care, be smart and educated, and you'll be okay.

Your best bet is using approved charging stations and approved on-board chargers - but we often have to "make do" with whatever electrical outlet we find. The manufacturers have spent megabucks developing a safe charging system. BUT, unfortunately, we cannot always charge through approved charging stations, and we often are faced with normal power outlets. High power portable charging stations do exist, and success with means understanding what kind of power outlet to use.

The need for safety: Done badly, it's possible to cause damage. The warning against extension cords isn't a whimsy, they're rightfully concerned about safety. Carefully done, you can safely ignore that warning, but you must know what you're doing. There have been multiple fires from electric cars being charged through substandard wiring. How? Bad wiring can easily cause enough heat to raise surrounding materials to the ignition point. This isn't a new issue since electrical fires have happened for as long as we've used electricity. Careful use of good quality extension cords and power outlets is the way to avoid an electrical fire.

We bought our electric vehicles to, for example, help the climate. Getting on the evening news by causing an electrical fire negates the gain you might have achieved.

The Electrical Code and power outlet ratings

The electrical code isn't an arbitrary set of nanny-state rules. It was developed through decades of experience and application of electrical engineering principles. Let's have a brief summary, and for many more details see Electric car charging within electrical code and power outlet limits

The "80% rule" says that continuous power through a plug/socket has to be 80% of the rated value. Electric car charging fits the definition of a continuous load, and therefore we must constrain ourselves by this rule. Hence for a "50 amp" power outlet, the charging rate must stay below 40 amps.

Ampacity is the measure of the maximum safe current (amps) we can use in a wire of a given thickness. Generally, the thicker the wire the more current it can carry. Wire thickness is measured in "gauge", and you may have seen this number used. A typical home extension cord is 14 gauge, for example. That wire gauge is completely insufficient and unsafe for the line-cord charger that comes with electric cars.

The 120 volt line-cord charger usually runs at 12 amps, and requires a 10 gauge extension cord. The 6 kiloWatt charging stations run at 32 amps continuous, and requires a 6 gauge extension cord.

General recommendations

The most correct electric car extension cord solution is to extend the J1772 connection. The J1772 extension cords (see the next section) are built to handle the load, with beefy wires and connectors.

That won't always be feasible, however.

With the 120 volt line cord charger it's quite feasible to use a 25 foot or 50 foot length of 10 gauge extension cord. A couple of these are listed below that are excellently built. The bright yellow color helps mitigate any tripping hazard.

For higher power there are several choices meant for 240 volt high power loads. The NEMA 14-50 cords should be used with the 6 kiloWatt charging stations, while the 6-20 and L14-30 cords should be used with lower rate stations. You will almost certainly need adapters - since the 6 kiloWatt charging stations universally use a NEMA 6-50 plug. A couple NEMA 6-50 to 14-50 adapters are listed below.

If you cannot find a suitable manufactured adapter, it's relatively easy to build an adapter.

JLong and De-ICEr - the best choice for an electric car extension cord

A common problem at public charging stations is ICE'ing. This isn't a winter phenomena, but is an acronym: Internal Combustion Engine.

What happens is gasoline car owners, whether unwittingly or on purpose, sometimes park in front of EV charging stations. See Charging station etiquette - effectively sharing limited resources

Rather than get stuck unable to charge, wouldn't it be useful to pull out a J1772 extension cord? That's the thought behind these two products. You'd have a J1772 extension cord, with all the necessary safety features built in (thick wiring and beefy plugs), that you can use to extend the reach of the charging station.

These extension cords can also be used at home. Say your charging station has a prescribed location, but your car has to park far away? The charging station might come with a 25 foot cord that doesn't reach the parking spot. What do you do? Use the J1772 extension cord.

The JLong 40 amp J1772 extension cable, from Quick Charge Power, and the De-ICEr 40 Amp 20 Ft J1772 Extension Cord for EV Charging Stations, from Electric Motor Werks, are both properly designed J1772 extension cords supporting a 40 amp continuous electrical load. Other J1772 extension cords max out at 32 amps, meaning the components aren't as high a quality. By supporting 40 amps, the wires are thicker, and the connectors more robust, making either a safer choice than the others.

I own a JLong, and am impressed with how solid and robust are the connectors. The cable is flexible enough to easily loop into a small bundle that's easy to carry in the trunk. Finally, there's a small but important detail - the charging handle can be locked using a simple padlock. This means your car won't be unplugged unexpectedly or at the very least the JLong won't be stolen.

J1772 extension cords are useful any time the charging cord isn't long enough to reach your car. Maybe you've been blocked from a charging station, but can park a couple stalls down. A J1772 extension cord like the JLong or De-ICEr gives extra reach.

Other extension cord choices for electric cars

The JLong isn't the only electric car extension cord choice. You can also safely extend the other side of the charging situation connection using a more traditional extension cord. This must be done with care, using extension cords meant for heavy duty usage. Fortunately these do exist.

120 volt cords for the line cord charger Every electric car comes with a 120 volt line cord charging station. Generally these run at 12 amps 120 volts, meaning the extension cord must be capable of running that much current continuously. Scroll down to the bottom of this page and you'll find a few such choices. If you're looking at extension cord packages in the store, study the writing carefully. It'll say the cord is rated for 10 amps, 15 amps, whatever, and that the cord is 12 gauge, 14 gauge, or whatever. The smaller the gauge number the thicker the wire - 10 gauge is the minimum recommended for this purpose. Again, scroll down to the bottom of this page and you'll find several extension cords meant for contractors.

240 volt 20 amp extension cords Several 3 kiloWatt charging stations are available in a tiny package that are easy carry around at all times. The Aerovironment TurboCord has the advantage of supporting both 120 volt 12 amp and 240 volt 16 amp. Scroll down to the bottom of the page and you'll find NEMA 6-20 extension cords that will work perfectly with the TurboCord.

240 volt 40 amp extension cords For higher power 6+ kiloWatt charging stations, you'll need a heavier-duty extension cord. Scroll to the bottom and you'll find several NEMA 14-50 or NEMA 6-50 extension cords. These handle 40 amps continuous and will do what you need. Most (all) of the charging stations shown here come with NEMA 6-50 plugs rather than 14-50 plugs. That means buying a NEMA 6-50 to NEMA 14-50 adapter, several of which are shown below, or else replacing the NEMA 6-50 plug from the charging station cord with a NEMA 14-50 plug.

Extension Cords

The following are some useful extension cords.

NOTE CAREFULLY: When in the store looking at extension cords, read the label carefully and look at the thickness of the wire. For charging an EV, we want at least 10 gauge thickness.

Some of these have a molded plug on one end, and bare wire at the other. That makes them excellent starting points for building adapter cords. It's also possible to buy an extension cord, cut off the ends, and attach other plugs, to build a custom adapter.

NEMA 14-50 extension cords

Camco 55195 50 AMP 30' Extension Cord with PowerGrip Handle: This cord is rated for 50 amps, uses 6 gauge wiring, and has NEMA 14-50 connectors on each end. That is an excellent combination that will handle pretty much any current load you can throw at it.

General Electric WX9X35 4-wire Range Cord, 4-foot: 40 Amp, 4 wire, Range power cord This 4 foot cord is rated 40 amps, 125/250 volts, with two 8 gauge wires and two 10 gauge wires. This cord is a useful starting point for building 14-50 adapter cables

PETRA 90-2028 10-Foot 4-Wire Dryer Cord: 40 Amp, 4 wire, Range power cord This 4 foot cord is rated 40 amps, 125/250 volts, with two 8 gauge wires and two 10 gauge wires. This cord is a useful starting point for building 14-50 adapter cables

Coleman Cable 09014 6/2 and 8/1-Gauge SRDT 50-Amp Range Power Supply Cord, 4-Feet, 3-Wire, 125/250V: Coleman Cable 09014 6/2 and 8/1-Gauge SRDT 50-Amp Range Power Supply Cord, 4-Feet, 3-Wire, 125/250V. Right-angle plug allows installation closer to the wall. Has a 3 prong plug. 50-Amp. 4-feet long wire with strain relief bracket to ensure safe installation.

NU-CORD 25 ft. 6/3 8/1 NEMA 14-50 RV Extension Cord: Using 6-gauge wiring and molded plugs, this extension cord has the heft required for the task at hand. The plug/connector ends have built-in handles for easier handling. Home Depot also carries a

Utilitech 6-ft 50-Amp 6-Gauge Black Indoor Extension Cord: This cord is rated for 50 amps, uses 6 gauge wiring, and has a NEMA 14-50 connector on one end. The other end has bare wires apparently meant to wire into some equipment, but of course you can attach another plug on that end. That is an excellent combination that will handle pretty much any current load you can throw at it.

NEMA L14-30 extension cords

Iron Box # IBX-5805-50M - 30 Amp L14-30 Generator Extension Power Cord - 4-Wire, 30A, 125/250V, UL LISTED: Heavy duty UL listed L14-30 generator extension cord rated for outdoor use. 50 foot length, uses a heavy duty flexible SJOOW jacket. For use with generators that feature an L14-30R receptacle. Cable generally extends another L14-30 power cord plug, or connects to a transfer switch or inlet box with a male L14-30P inlet.

Conntek 20602 50-Foot 10/4 30 Amp 125/250 Volt 4 Prong L14-30 Transfer Switch Cord/Generator Extension Cord: Generator Extension Cord, 3 Pole, 4 Wire Grounding, NEMA L14-30P to NEMA L14-30R Max Power: 7500W, Stays flexible in cold weather, Heat Resistant up to 221F Application:Transfer Switches, Generator,...etc. Approval: Plug, Connector, : UL, C-UL Cable: 50FT STW 10/4 rating:30A 125/250V

Coleman Cable 01912 25-Feet 10/3 Generator Power Cord with L5-30P Plug and 3-Outlets: The Coleman Cable 01912 25-foot 30 Amp 10-gauge Tri-Source (locking male) generator cord plugs into 30 Amp locking outlets on a generator. The Tri-Source female end provides three extra 15 Amp standard outlets, while the vinyl jacket protects against moisture, abrasions, and exposure to sunlight. The cord features one male 5-20P plug with three 5-15 female outlets, is rated for rugged outdoor use, and is engineers specially to work with portable generators.

NEMA 6-50 extension cords

Milspec Direct 25-Foot 8-Gauge STW Pro Grip 40A Welding Extension Cord for Portable Welders, Black: Professional quality patented Pro Grip lighted welding extension cords bring power to where you need it. Todays portable welders have power supply cords that are much too short. Rated at 50A-250V (NEMA 6-50), each extension cord features two clear neon lighted ends that allow you to make sure power is flowing through your cord. In addition, the bright neon lit ends illuminate in the dark and visually makes the connects and disconnects easier to do. The specially crafted, high visibility jacket on Pro Grip cords are designed to be Flame Retardant (FT2), Water Resistant (WR), and Cold Weather Resistant (-40F). Patented Pro Grip nylon handles make pulling apart plugs and connectors from each other easier with less effort and stress. Pro Grip handles easily fold away when not in use.

Coleman Cable 1917 8/3 STW 6-50 Welder Extension Cord, Blue, 25-Foot: Coleman Cable 1917 8/3 STW 6-50 Welder Extension Cord, Blue, 25-Foot. 8-Gauge plug. Stw jacket for heavy-duty performance. Lighted receptacle end indicates when power is on. Molded ends offer safety and convenience on the jobsite. Bring portability to welding machines and create convenience. Provide a convenient, safe method to extend the range of welding equipment. Intended for new commercial construction, mro industrial and general welding.

NEMA L6-30 extension cords

NEMA L6-30 Extension Power Cord - 20 Foot, 30A/250V, 10/3 SJOOW - Iron Box Part # IBX-5803-20: NEMA L6-30 extension power cord allows you to extend an L6-30P power cable up to 20 feet. Rated for 30 Amps, 250 Volts. L6-30P plug to L6-30R connector.

L6-30 Extension Power Cord, 15 Foot - 30A, 250V, 10/3 Wire: A 15 foot L6-30P to L6-30R locking extension power cable, rated for 30 amps and 250 volts. Used typically in rackmount PDU's, servers, UPS, and generators.

NEMA 6-20 extension cords

NEMA 6-20 Extension Power Cord - 25 Foot, 20A/250V, 12/3 SJT - Iron Box # IBX-6153-25M: This is a simple 25 foot extension cord with molded plugs for NEMA 6-20. It would be a great companion to the AeroVironment TurboCord shown above.

Stanley 31626 Grounded 250-volt Heavy Duty Appliance Pro Extension Cord, 6-Feet, Gray: This Stanley Appliance Pro heavy duty 6-Foot extension cord will handle most of your appliance needs where the distance to the outlet occurs. It is a 250 volt cord and has a gauge of AWG 12/3 SPT. The Right angle plug will sit flat against the wall. It has a heavy duty vinyl insulation.

NEMA 5-20 extension cords

Yellow Jacket 2806 10/3 Heavy-Duty 15-Amp SJTW Contractor Extension Cord with Lighted End, 100-Feet: Yellow Jacket 2806 10/3 Heavy-Duty 15-Amp SJTW Contractor Extension Cord with Lighted End, 100-Feet. Super flexibility in cold and hot weather. Power Lite power indicator lamp glows through the extra heavy, clear molded plug when the cord has power. Three times as abrasion resistant as standard vinyl, making these cords the toughest on the jobsite. Extra heavy, clear molded plugs are rugged, durable and oversized. Meets OSHA specifications, UL Listed. 10 Gauge.

100 ft. 10/3 SJTW Extension Cord with Lighted Plug: Meant for heavy-duty applications, this 10 gauge cord is also light-weight and easy to roll into a compact unit.

Utilitech 50-ft 20-Amp 110-Volt 10-Gauge Yellow Outdoor Extension Cord: This cord is rated for 20 amps, uses 10 gauge wiring, and has a NEMA 5-20 connectors on each ends. The connectors light up when powered, and the bright yellow color should mitigate tripping hazards. That is an excellent combination that will handle your line cord charger with ease.

Commercially built adapters

NEMA 14-50 to TT-30

Camco 55185 PowerGrip 30M/50F AMP 18 inch Dogbone Electrical Adapter with Handles 3750W/125V: This adapter converts between NEMA 14-50 and NEMA TT-30P (30 amp).

Camco 55175 18 inch PowerGrip Dogbone Electrical Adapter with Handle: This adapter converts between NEMA TT-30P and NEMA 14-50 (30 amp).

NEMA 6-50 to L14-30, 240 volt 30 amp

NEMA 6-50 to 14-50, 240 volt 50 amp

NEMA L14-30P to NEMA 14-50R, 240 volt 30 amp

NEMA 14-30P to NEMA L14-30R

NEMA L14-30P to 6-15/20R

NEMA-L5-20R to NEMA-5-20P, 120 volt 20 amp

Ground Fault protection

Charging an electric vehicle is almost certainly going to happen outside. It might be raining. Water and electricity is of course a bad idea. GFCI plugs are designed to make it safe.

Voltec 04-00102 12/3 STW 20 Amp GFCI Power Block Adapter with Lighted End, 3-Foot, Blue with Yellow Stripe: 20 amp in-line GFCI adapter with lighted power block, length: 2ft, gauge: 12/3, wire type: STW, 3 outlets, plug type: 5-15P, receptacle type: 5-15R, 20 amps, rating watts: 1875. In other words, this is a short extension cord with GFCI. It is only suitable for a level 1 charger, but will be good insurance.

Tower Manufacturing 30396500-08 20 amp Line And Load Side User Attachable In-Line GFCI With Manual Reset: This unit fits over a cord, giving you strong protection from the elements, while providing GFCI protection.

Leviton WT899-W 20-Amp 125-Volt SmartLock Pro Slim Weather-Resistant and Tamper-Resistant GFCI Receptacle, White: A regular power outlet with GFCI protection. For use in the field, you can install this in a junction box and run wiring into it. However, it is little better than the extension cords, and of course this is limited to level 1 charging.

Tower Manufacturing 30339005 15 amp 3-Wire GFCI Outlet Adapter: 15 amp 3-wire ground fault circuit interrupter (GFCI) outlet adapter for converting standard indoor electrical outlet into GFCI outlet to protect from shock, electrical fire or electrocution. This is an in-line plug/socket making it a little simpler to use than an extension cord. However, it is only rated for 15 amps limiting its usefulness somewhat.

Farm Innovators CC-2 Cord Connect Water-Tight Cord Lock - Green: This is not a GFCI protector at all, instead it fits over cable connections, giving strong protection against the elements.

Sockets and Plugs

NEMA 14-50 - 240 volt 50 amp

NEMA 6-50 - 240 volt 50 amp

NEMA L14-30

NEMA L6-30 - 240 volt 30 amp

NEMA L6-20

NEMA 6-50, 6-30, 240 volt, 50 amp, 30 amp

Cooper Wiring Devices S42-SP-L Commercial Grade Angle Vinyl Power Plug with 30/50-Amp, 250-Volt, 6-30/6-50-NEMA Rating, Black: The commercial grade angle power plug has feature dual current model furnished with blades. Terminals have pressure plates to protect wires. This device is constructed of abuse-resistant thermoplastic. 30/50-amp, 250-volt, 6-30/6-50-NEMA rating and 3-pole, 3-wire grounding configuration. Available in black color. Measures 2-7/8-Inch length by 1-3/8-width by 3-3/8-Inch height.

Leviton 931 30/50 Amp, 250 Volt, Plug, Angle, Grounding, Black: * 2 pole, 3 wire grounding dual power angle plugs with interchangeable blades * Dual power vinyl angle plug - interchangeable blades * 250 Volt * 60 Hz AC Grounding * Molded of tough, black vinyl * Heavily plated steel cable clamp concealed in plug-protected from wear prevents catching on equipment or clothing * Meets all range, dryer and other heavy duty cord requirements * Color-coded terminal screws accept up to No. 6 stranded conductor * Terminal screws are backed out and staked * 3.484"L x 2.562"W x 1.427"D * 30/50 Amp * Maximum cord diameter -.630 - 1.050" * Interchangeable blades * NEMA (6-30P) (6-50P) * Black height.

NEMA 6-20

Leviton 620PV 20 Amp, 250 Volt, Plug, Grounding, Yellow: 20 Amp, 250 Volt, NEMA 6-20P, 2P, 3W, Plug, Straight Blade, Commercial Grade, Grounding - Yellow


Heavy duty wire/cable

Wire Cord, 50 Ft, Rubber Coated, 10 Gauge, 4 Conductor (10/4) 600v SOOW: 50 foot long Rubber SOOW cord is designed for indoor or outdoor applications. 4 conductors can be stripped and installed in many types of power connectors including L14-30, 5-30, 6-30, 7-30, 24-30, 10-30, 11-30, 15-30 or 18-30. Suitable for use with RVs, Generators and Theater lighting.

Coleman Cable 09607 10/4 Bulk Wire, 25-Amp 10-Gauge 25-Feet: Coleman Cable 09607 25-Feet Bulk Wire 10-Gauge 4-Cond SJEOOW Seoprene Rated 105-Degree Celsius, 10/4 Flexible and tough jacket. Offers -50-Degree Celsius to 105-Degree Celsius temperature extremes. Seoprene offers excellent abrasion, ozone, sunlight, chemical and oil resistance as well as water and mold resistant non-wicking lightweight polypropylene fillers. Water resistant with high dielectric insulation. Lightweight, long lasting, easy to carry and easy to handle. All components are recyclable and non-hazardous for environmental landfill disposal. Color coded conductors for easy identification. This type of wire has many applications, they include Special uses requiring flexibility and mechanical toughness, high environmental resistance and flame retardance. Push button remote controls. Motor control, stage equipment and lighting. Industrial control and robotic systems. Outdoor applications. Suitable and approved for submersion in water.

Safely use Extension Cords when charging an electric car or electric motorcycle

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