50 ft extension cord - 14 gauge - Is it safe to use?

dono, will it handle at least 15 amps continuous current? if so then yes. that's 1650 watts

 

I've used a 25 ft 12 Gauge for over 6 years (mostly with 2012 PIP), and it works fine. The TOTAL length is 50 ft;
I wouldn't go longer.

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You would be safer with a 12 gauge extension cord. I wouldn't recommend using a 50 foot 14 gauge cord for charging your Prius.

 

It's safe, under some conditions.

Basically the problem is heat.

If the wire is kept stretched out and in a reasonably cool environment, it's probably safe. It should be noted that the EVSE the car came with uses a 14 gauge cable. I've been using it coiled and it's been fine, but it's 105°C rated cable, while many extension cords are 85°C or even 75°C rated. Because of that difference, I generally recommend 12 gauge if you're going to use an extension cord, especially if it's going to be either in the sun or in a hot environment like an uninsulated garage in the summer sun.

 

What if you dropped the current to 8 amps? There is a setting in Charge Settings instead of maximum current you can use 8 Amps, so 110 V x 8 A = 880 Watts. This would also mean 10 hours of charging I would think, but so what, you're charging it overnight anyway, right?

 

if you do go with it, check the plugs at both ends frequently, they tend to heat up faster the the cable itself.

 

yup, that would work

 

Very important point. Start with the receptacle. If it has a lot of years or a lot of use, replace it. Buy the $2.59 receptacle, not the 59¢ one. You want good, tight contacts inside the receptacle with both the wires and the plug blades. Be sure the plug blades are clean and in good condition, not bent. Do touch all the parts occasionally. If you feel warmth, upgrade the parts.

 

here's a 12 Gauge 50 foot

 

I build my own and they last. I use #12 and #10 gauge "cabtire" cable. They are very expensive. The one I made to power the garage before I installed buried cable cost me $150. But it doesn't heat up, even when block heaters are plugged into it. The old type "immersion" heaters, that actually heat the block, that draw more than 900 W. The one in my old Subaru was 1700W. The heater blew warm air as soon as the car was started!

Do consider the outlet you are plugging into uses 14 gauge wire from the breaker box and could be 50 feet long. As stated above, as long as it's not left coiled up the heat shouldn't cause any problems, though that from someone living where 30C is "hot".

 

For reference, a hair dryer draws about 15A, a vacuum cleaner draws about 12A and a big garbage disposal draws about 8A. The difference here is the length of time - hours instead of minutes.

I've been charging my Prime off a 15A circuit with a 35 foot 12awg extension cord tied to the loosely coiled up EVSE. The thing that gets the warmest is the EVSE cord near the velcro band tying it together and that's only about 15°C above ambient.

 

You could check the temperature by feel which might be good enough but I would think using an infrared thermometer would be even better, especially to detect if the temperature of the cable is rising which would be hard to do by feel. I would think an inexpensive thermometer would be accurate enough.

 

Thanks! I just ordered one. It looks like a handy tool to have.

 

Any chance of someone tripping on the cord ?

 

The circuit you intend to use is a 15 Amp one. They usually dedicate a breaker for the air conditioner, as they tend to operate near max current when starting up. You should be able to charge at the higher rate. Do note, if there is voltage drop in the extension cord the current may go up to compensate. I would purchase a 12 gauge cord.

Oh, and yes, the tripping hazard would be greater than the electrical hazard.

 

At 50 feet you should be using a No. 12 wire size. Don't cheap out on this. Too light of gauge is a fire hazard. I would use an outdoor cord, and build it myself with the proper HD ends.

 

As previously touched on, a thicker cord will reduce electrical resistance and therefore heat. It takes energy to produce that heat, which means that a thicker cord will save you a bit of energy.

For example, the American_wire_gauge Wikipedia article gives the resistance in milli-ohms per foot for various wire gauges.

• 14 gauge: Resistance = 2.252mOhm/foot * 50 feet = .113 ohms. Voltage drop = (.113ohms*15A) = 1.69V Power used = (1.69V*15A) = 25.3 watts
• 12 gauge: Resistance = 1.588mOhm/foot * 50 feet = .079 ohms. Voltage drop = (.079ohms*15A) = 1.19V. Power used = (1.19V*15A) = 17.9 watts

So, you can save about 7 watts during charging by using the thicker cord.