Big black block!

Make sure the extension cord can handle the electrical load!! Just ask any electrician and they should know.

 

Do NOT leave it on the pillar though.
Take it with you when you are out riding, enjoying your car.

 

Here's something:

extension cord specs | PriusChat

IIRC the Owner's Manual says to not use an extension cord, but that maybe their lawyer's talking?

 

It must be the lawyers, because there is no technical basis. The wiring to a 15A receptacle is 14 gauge solid copper back to the breaker panel, and there is no way to tell how far that is. Even a 50 foot 12 gauge extension cord added on will have negligible voltage drop, so I would use a 12 gauge as the extension cord. I travel with a 25 foot cord and use it frequently with no problems.

 

I’d respectfully disagree. There is a specific reason, aside from the general risk that an extension cord might be improperly selected or used. One safety feature of the Toyota charging cable is a temperature sensor in the plug, mentioned on page 4 of the Quick Guide (PDF):

● Temperature detection function
A temperature detection function is equipped to the plug. While charging, if heat is generated due to looseness on the outlet side etc., this function suppresses heat by controlling the charging current.​

An extension cord wouldn’t have this feature, so there would be no active protection against temperature rise at the outlet. This shouldn’t be a problem, of course, if the outlet and plug are of the proper type and in good condition, but that may not always be the case.

For anyone who chooses to use an extension cord despite Toyota’s warning, it’s important to be sure that the plug is fully inserted into the outlet and makes good contact. If the plug is loose, the contacts in the outlet are worn out, and the outlet should be replaced. This might be a good idea, anyway; a hospital-grade (green dot) or specification-grade (Fed. Spec.) receptacle would be preferred, since these are designed and tested for better mechanical performance, further reducing the risk of overheating due to a poor connection.

 

an electrician would want you to keep the extension cord no longer than 6 feet with #12 wire minimum. Even more important - ascertain what other loads may be on that circuit, as pulling ~1kW will likely cause its breaker to trip, unless its 20amps.
.

 

There is some other basis for not recommending the use of extension cords:

• Extension cords are subject to wear and physical damage. If someone trips over it or walks on it, that could damage the wires or wear the insulation. The EVSE is designed with a much thicker cable to withstand this abuse.
• An extension cord likely has the receptacle end sitting on the ground, so it is more likely to get wet if there is water on the floor. Theoretically this problem is mitigated by using a GFCI outlet or portable GFCI with the extension cord, but it's better for the connection not to get wet in the first place. Besides possibly causing a shock hazard, frequent exposure to water could corrode the connections in the end of the extension cord or maybe the plug (but the contacts on the plug look very shiny and corrosion resistant).
• Finally there is the fact that people unfortunately can't be trusted to pick an appropriately rated cord. Many cheaper cords are rated for 13A and use 16 gauge wire, and those are not sufficient for charging at 12A (since the cord should be derated to 80% for continuous loads). Obviously this is the one the user has the most control over.

Personally I think the risk of using an extension cord is low as long as you understand the potential issues. I use a 12 gauge cord instead of 14 gauge for additional durability. And I use the shortest practical length of extension cord (15 feet is enough in my garage).

That's all wrong, or at least misleading. At 6 feet, 14 gauge wire is fine. 12 gauge is better to withstand more physical damage, but I don't think you'll be able to find a 12 gauge cord that short unless you special order it. And you can certainly go longer than 6 feet if you need to, just keep the cord as short as practical.

It will only trip the circuit if there are other significant loads. A 15A circuit is fine for charging if it's lightly loaded otherwise. I measure around 1350W when mine is charging. That leaves around 90W for things like lights without exceeding the 80% derating of 12A (of course watts depends on the voltage and I forgot to check current. But I think the voltage was still around or over 120). In a single family house you can easily find out what's on the same circuit. In an apartment or commercial building it might not be obvious so you should be cautious or check with building management to be completely sure.

Here are some short extension cords to consider:
15ft 12 gauge: https://www.lowes.com/pd/Utilitech-Pro-15-ft-12-AWG-3-SJTW-15-Amps-Lighted-Extension-Cord/3191739
6ft and 10ft 14 gauge 15A, but not rated for outdoor use: Monoprice Extension Cord - NEMA 5-15P to NEMA 5-15R, 16AWG, 13A, 3-Prong, Black, 2ft - Monoprice.com
You can also get heavier duty cords from McMaster-Carr, including 6ft 12 gauge cords. The abrasion resistant cords would be appropriate, but they are only available 25ft or longer.

 

That would not be a good reason to specify not using extension cords. Anybody who can't pick an appropriately rated cord is likely not reading the owner manual in the first place.

The electrical code (NEC 2017) also requires in Article 625 (Electric Vehicle Charging Systems) that the circuit used to charge the car shall have no other outlets (an outlet is defined as "A point on the wiring system at which current is taken to supply utilization equipment"). In other words, a dedicated circuit. I doubt most garage outlets meet this requirement, particularly in 1980's homes where the garage outlet may be on the same circuit as exterior outlets and a bathroom or two.

625.40 Electric Vehicle Branch Circuit. Each outlet installed for the purpose of charging electric vehicles shall be supplied by an individual branch circuit. Each circuit shall have no other outlets.​

 

But it is a good line for Toyota lawyers to point to when someone sets their house on fire by overheating an undersized/poorly made extension cord.

My view is that its in there for lawsuit proofing, not because its necessarily dangerous. Just need to take appropriate precautions (correct sizing, protection against the weather, minimize tripping hazard, etc). Plugging it into a GFCI on a dedicated circuit is also a plus, where possible.

 

I’m not sure that was the intention of the code-making panel. Notice how they wrote “outlet installed for the purpose of charging electric vehicles” (emphasis added), that is, if you put in a new outlet for EV charging, it has to be on its own branch circuit. In 625.44, Equipment Connection, which says what outlets can be used, there is no requirement for a dedicated circuit.

 

Good point. I looked in the 2007 NEC and there is nothing in there that requires this temperature sensor. I haven't located the applicable UL document for EVSE equipment - UL 2594-2013.

In my garage this morning during a 50% charge this morning, the wall mount metallic surface mount box was slightly warm to touch just above the outlet in use. Heavy duty Leviton outlet, 15A, The ambient was 82F, the hot spot was 99F.

This article deals only with equipment connections, not the branch circuits themselves. 625.40 is specific to EV branch circuits.

 

Why not the heavy duty one? it's the same price as the medium duty one.
https://www.lowes.com/pd/Utilitech-Pro-15-Ft-12-3-SJTW-Yellow-Extension-Cord-w-Indicator/1003051800