ev charging

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Safely using extension cords when charging electric cars, electric motorcycles, electric bicycles

Your electric vehicle was supposed to transport your butt around town and beyond. Despite the ideas of conventional wisdom (50 or 80 mile range means the EV is only suitable for around-town use) you don't have to be limited to traveling a short distance from your home. Instead, you can take longer trips by charging, at the highest rate possible, as you travel. Success means having the flexibility to use any power outlet you find, and having the equipment to maximize the charging rate to minimize the charging time. It's going to mean developing the skills to build electrical adapter cables to match any power outlet, and a bit of knowledge about the safe power level for a given cable or power outlet.

We must do this safely, because it's possible to cause damage. Some of the manufacturers warn you to not use an extension cord when charging an electric vehicle. With care you can safely ignore that warning, but of course 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. With good quality extension cords and adapters, you can charge electric vehicles anywhere there's electricity. 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.

Currently the charging station network is insufficient for every place we want our electric cars to take us. You don't have to be limited to the public charging station network, and you don't have to be limited to 120 volts 15 amps (1.4 kilowatts) as the only fallback. A portable high power charging station, along with suitable adapters and extension cords, means - for example - you can stop at a laundromat or RV park, plug into the high power electric outlets, and charge at 5+ kilowatts while on the road.

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 general principles are:

  • Check carefully the power socket rating
  • Check carefully the wiring to the power socket
  • Use heavy duty cables with high enough gauge to handle the current
  • Don't use cables that are frayed or broken
  • If you can, adjust the vehicle charger to not draw more current than you know is safe
  • Your power is limited by the weakest link in the chain
  • Check whether cords or connections are getting hot while in use
  • Use the shortest length of cord possible

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.

Electrical codes will be violated. We're going to create adapters here with the potential to connect a 240 volt 50 amp source to a receptacle rated for 120 volts 20 amps. That's obviously not to be used for general purposes, because running 6+ kilowatts through a 120 volt 20 amp plug will give you a fire. In other words, don't build a NEMA 14-50 (240 volt 50 amp) to NEMA 5-20 (120 volt 20 amp) adapter, then use it to run a 240 volt 6 kilowatt charging station, because that 5-20 plug will fry like a marshmallow. But it's perfectly alright to connect from a 120 volt 20 amp outlet to an adapter ending in a NEMA 14-50, and then to equipment compatible with both 120 volt and 240 volt inputs, so long as the equipment can be adjusted to not draw more than 120 volts 20 amps.

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. A 240 volt 50 amp outlet is capable of sending 10 kilowatts of electricity. 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, but successfully using one means understanding what kind of power outlet to use, and using adapters to adjust for the power outlets we find in the wild.

You might find in actual practice that using long skinny extension cords just results in a warm cord, with no fire. That was claimed in a discussion on this site several years ago. But there are enough instances of fires, that it pays to be cautious.

At 120 volts 12 amps (typical line charger sold with the car) it takes 20ish hours to recharge cars like the Leaf. The question you or your electrician have to answer is: Is the outlet you plan to use safe to be used at 120 volts 12 amps for 20 hours at a time? If not - upgrade the wiring - upgrade the circuit breaker - upgrade the power outlet - whatever it takes to be safe.

Portable high power charging stations

The electric cars are all sold with a 120 volt line charger that doesn't seem to be meant for anything but the occasional charging session when you have no other choice. They're good for a 1.5 kilowatt charge rate, which is good for 5-7 miles of range per hour of charging. But, we want something faster than that because we have better things to do with our time. At home 120 volt charging may be fast enough, but in public it rarely is.

It's possible to have the line charger upgraded - http://evseupgrade.com does so for a fee. But some companies are making 240 volt portable chargers. Either way supports charge rates around 5 kilowatts. That's starting to be some serious charging - if you can find compatible power outlets. Further down this page we talk about the extension cords and power adapters required.

Several vendors make 6.6 kilowatt charging stations that are small/light enough to consider carrying in the car during a trip. They all have a three-conductor cord which the vendors usually recommend hard-wiring to the electrical service panel. However, it's quite possible to attach a NEMA 14-50 plug (see below) to the end of the cord. Then, with suitable extension cords and adapters, the charging station can be plugged into power outlets you find on the road.

Typical charging stations support about 30 amps (about 6 kilowatts) and probably don't work well at 120 volts. Therefore a 120 volt 20 amp outlet, or even 240 volt 20 amp outlet, cannot be used unless the charging station power level can be adjusted. Some of the electric cars let you adjust the charging rate, and you should do so whenever charging through a low power outlet. You'll be avoiding popping the circuit breaker, or worse.

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.

120 volt 20 amp 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's only suitable for a level 1 charger, but will be good insurance.

120 volt 20 amp 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.
120 volt 20 amp 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's little better than the extension cords, and of course this is limited to level 1 charging.
120 volt 15 amp 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's only rated for 15 amps limiting its usefulness somewhat.

0 volt 0 amp 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.
240 volt 30 amp Square D by Schneider Electric QO230GFICP QO 30-Amp Two-Pole GFCI Breaker: Circuit breakers provide GFCI protection behind the power socket. Where the manufacturers don't seem to build higher power extension cords with GFCI, you could build a junction box containing one of these GFCI circuit breakers, to get portable GFCI protection. This one supports the low end of Level 2 charging.

Double Pole GFCI Circuit Breaker, 60 Amp supports the 240 volt 50+ amp rate necessary for high power charging at the upper end of Level 2.

Square D by Schneider Electric HOME250SPA Homeline 50-Amp Spa Panel provides you with the circuit breaker built into a weatherproof junction box, at a very reasonable price, ready to go. This is meant to be mounted on a building to protect something like a hot tub. At 9.6 x 5.3 x 4.4 inches in size and about 5 lbs weight, I see no reason it couldn't be carried around especially for long trips.


The AC power system in the U.S. uses single phase AC at either 120 volts or 240 volts, though you'll also find commercial buildings with 208 volts. In Europe or elsewhere you'll find three phase AC sockets available. I don't know what to do with those, but most electric vehicles can only charge off single phase power sources.

Unfortunately there are a plethora of power outlets for 240 volts, in the U.S. and perhaps elsewhere.

Fortunately all the power outlets use three wires whose purpose is the same: Two wires are "hot" (carry the AC voltage) and the third is the neutral wire.

Generally speaking, building any adapter follows these steps:

  • Get a short length of 3-wire cable of the appropriate gauge, the thicker the better
  • Strip the ends so you have bare wire - for some adapters you'll only strip one end
  • Open up and study the plugs for each end of the adapter, making sure you understand where the two hots and neutral are
  • Insert the stripped ends into the plugs, tightening down screws, making sure the connectors on each end match up correctly
  • Tighten down strain relief, and otherwise reassemble the plugs at each end


That's what one end of a fairly typical adapter might look like.


And this is a couple completed adapters. At one end is a NEMA 14-50 enclosure - because the charger system in my car uses NEMA 14-50 plugs. Those are rated for 240 volts 50 amps, as we noted earlier. The adapters shown here are for the L6-30 (240 volt 30 amp) and 6-20 plugs (240 volt 20 amp).

NEMA 14-50 to TT-30P Camco 55185 PowerGrip 30M/50F AMP 18" Dogbone Electrical Adapter with Handles 3750W/125V: This adapter converts between NEMA 14-50 and NEMA TT-30P (30 amp). Camco 55175 18" PowerGrip Dogbone Electrical Adapter with Handle does the same conversion, but reverses the gender of the two ends.
NEMA-L5-20R to NEMA-5-20P, 120 volt 20 amp Tripp Lite P044-06I 6 inch 12AWG Heavy Duty Power Adapter cord (NEMA-L5-20R to NEMA-5-20P): 6-inch 12AWG Heavy Duty Power Adapter cord (NEMA-L5-20R to NEMA-5-20P). Locking 120V 20A (NEMA L5-20R) output receptacle and a straight-blade 120V 20A (NEMA 5-20P) input plug
NEMA L14-30P to NEMA 14-50R, 240 volt 30 amp Conntek RV Generator Adapter with 30 Amp 4 Prong Locking Male Plug To RV 50 Amp Female Connector

Sockets and Plugs

NEMA 14-50 - 240 volt 50 amp Camco 55353 50 AMP Female Replacement Receptacle and Camco 55255 50 AMP PowerGrip Replacement Plug are excellent choices for NEMA 14-50 cords
NEMA 14-50 - 240 volt 50 amp Leviton 55050 50 Amp, 125/250 Volt, NEMA 14-50R, 3P, 4W, Surface Mounting Receptacle, Straight Blade, Industrial Grade, Grounding, Side Wired, Steel Strap, Black
NEMA TT-30P Camco 55283 30 AMP Mini Replacement Male Plug with PowerGrip Handle and Camco 55343 30 AMP Female Replacement Receptacle
NEMA L14-30 - 240 volt 30 amp 4 pins Socket, NEMA L14-30 30 Amp, 125/250V Twist Lock and Leviton 2711 30 Amp, 125/250 Volt, NEMA L14-30P, 3P, 4W, Locking Plug, Industrial Grade, Grounding - Black-White
NEMA L6-30 - 240 volt 30 amp Leviton 2621 30 Amp, 250 Volt, NEMA L6-30P, 2P, 3W, Locking Plug, Industrial Grade, Grounding - Black-White and Leviton C2623 30 Amp, 250 Volt, NEMA L6-30R, 2P, 3W, Locking Connector, Industrial Grade, Grounding, Black-White
NEMA L6-20 - 240 volt 20 amp Leviton 2321 20 Amp, 250 Volt, NEMA L6-20P, 2P, 3W, Locking Plug, Industrial Grade, Grounding - Black-White and Leviton 2323 20 Amp, 250 Volt, NEMA L6-20R, 2P, 3W, Locking Connector, Industrial Grade, Grounding - Black-White
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.

NEMA 6-30P 240 volt, 30 amp 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 6-20 240 volt, 20 amp 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

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 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's an excellent combination that will handle pretty much any current load you can throw at it.

It's primarily sold for the RV/Camping crowd because lots of RV parks have NEMA 14-50 outlets available. Ergo, an electric car owner could carry a portable 5 kilowatt charging station, and with one of these cords, along with suitable adapters, go into any RV park to charge their car.

Conntek RL14305 RV 50-Amp 25-Feet Heavy Duty Extension Cord: is a similar cord from a different manufacturer.

NEMA 14-50 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
NEMA 10-50 240 volt 50 amp

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.
NEMA L14-30 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

NEMA L14-30 to 3x 120 volt 20 amp outlets 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, 240 volt 50 amp 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. Today's 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.
NEMA 6-20, 240 volt 20 amp 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, 120 volt 20 amp 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.


4 conductor 10 gauge 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.
4 conductor 10 gauge 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.

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EV Charging, charging stations, extension cords, charging networks, etc

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Electric vehicle charging standards

The following comes from a presentation at PlugIn 2010 - "The Near Future of Charging Panel AC vs. DC, slow vs. fast – the outlook for charging technologies". The presenters were all members of the SAE committees defining EV (automobile) charging standards.

SAE standards have defined six models of electric vehicle charging. Many have been thinking "Level 1" is regular US household outlets, "Level 2" is the EVSE equipment being deployed for cars, and that "Level 3" is the DC Fast Charge system. The panel presentation was meant to get us straight on what the SAE committee's have been discussing to organize the charging system.


AC Charging DC Charging
AC Level 1 120 V AC Single phase; max 16 amps; max 1.9 kw DC Level 1 200-450 V DC; Current <= 80 amps; power <= 19.2 kw
AC Level 2 240 V AC Single phase; max 80 amps; max 19.2 kw DC Level 2 200-450 V DC; max 200 amps; max 90 kw
AC Level 3 Not defined yet but they might do so, might cover AC three phase DC Level 3 TBD, may cover 200-600 V DC; may cover up to 400 amps; may cover up to 240 kw

Essentially "Level 3" doesn't exist yet and the charging standard everybody has been thinking of as "Level 3" is really either "DC Level 1" or "DC Level 2".

There are unfortunately several kinds of connectors being used:


The AC Level 1 connector we all use in our homes isn't shown. The top connector is the J1772 connector that all the automakers have agreed on. The bottom one is a proposal for DC Level 2 which combines the J1772 connector with a couple extra pins for DC charging.

The connectors defined for Europe are different from the ones defined in the US and Japan. The signals are all the same on the connectors, just the connector shapes are different. Also Japan has defined a DC Fast Charge system, CHAdeMO, which is popular in Japan but the SAE committee is apparently reluctant to adopt.


IEC 62192-2 Type 1 is approximately the same as the J1772 connector. However IEC 62192-2 Type 2 is not.

The pinouts of some connectors under discussion are as follows.


charging ev with solar alternator battery dc to ac convertor

comments needed pro and con . im trying this , i have small dc motor which 3 15 watt solar panels in sunlight spin motor just fine direct , running to wired alternator via belt wire to 12 volt battery then to dc to ac convertor which could handle my 10 small 12 volt chargers 4 amps ..???????????? trying here , perhaps reaching on this ,,,, lonnie

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