Anyone know if it safe to charge via 220v extension cord?

[dgilles428]

As long as the extension isn’t too long and is sized properly it shouldn’t be a problem. Extensions made for 50 amp RVs would work well but can be expensive. Here’s an example.

I unplugged my 240 volt Ford EVSE and used an extension cord like the one shown to allow my brother in law to charge his Tesla in my driveway, I think he charged at 38 amps.

Sponsored

 

[hartmms]

Powering a camper or RV is nothing compared to EV charging.

It depends. When my RV (50amp service) has both AC units running, it pulls around 40amps from the shore power. The mobile chargers use 32amps. I use 50' total of extension cord. They use 6 AWG conductors. The drawback, as mentioned, is that a 30' 6/3 + 8/1 (3 power, 1 ground) extension cord runs around $150-$200.

 

[HuntingPudel]

It depends. When my RV (50amp service) has both AC units running, it pulls around 40amps from the shore power. The mobile chargers use 32amps. I use 50' total of extension cord. They use 6 AWG conductors. The drawback, as mentioned, is that a 30' 6/3 + 8/1 (3 power, 1 ground) extension cord runs around $150-$200.

The difference is that the A/C units have thermostats that cycle them on and off. The EVSE is continuous for multiple hours, which really stresses the circuit thermally. This is why it's important as @Maquis said to make sure that the cord is not coiled or otherwise in contact with itself and that you're using a correctly over-rated cord. ??

Another issue with a lot of extension cords is that the interface between the wire and the terminations sometimes is not up to snuff. The increased impedance at the connection point will sometimes lead to melting of the cable head and/or burning up the conductors at the point of connection. ??

 

[DevSecOps]

Anyone purchasing a J1772 extension should be aware that 95% of them are only rated for 40 amps. Ones made by Tuscan EV are rated to 50. If you hard wired you should ensure you get the right extension.

 

[glenthompson]

Powering a camper or RV is nothing compared to EV charging.

Depends on the RV. My motorhome has 3 roof AC units, washer/dryer, dishwasher, induction cooktop, and a bunch of electronics. In very hot weather it’s not uncommon to draw close to 40 amps.

 

[generaltso]

Depends on the RV. My motorhome has 3 roof AC units, washer/dryer, dishwasher, induction cooktop, and a bunch of electronics. In very hot weather it’s not uncommon to draw close to 40 amps.

Sure, but I bet it doesn't draw 40A continuously for 8 hours. All of those appliances you mentioned will cycle on and off.

 

[glenthompson]

Sure, but I bet it doesn't draw 40A continuously for 8 hours. All of those appliances you mentioned will cycle on and off.

In very hot weather and no shade the AC units will run almost continuously. If the AC does cycle off, the starting current is very high.

With any extension cord what really matters is the length, wire gauge, and connectors. Too long and you have to worry about voltage drop - not really a problem in the 30-50’ we’re talking about. If the extension cord doesn’t specify the wire gauge used that’s a problem. Poorly made plugs and receptacles can cause a lot of heat. When I buy outdoor extension cords I only get 12ga ones. Don’t want to take a chance with my power tools.

This Lectron extension from Home Depot only uses 8ga wire for the main power. The extension cords mentioned are using 6ga wire.

 

[JJR]

We have an emergency generator because we lose power 1-2 times a year and with Sandy years ago we were out for two weeks. The problem is the generator was installed before we had an EV and the EV plug is not on the panel that is powered by the generator. I could reach a powered 220v outlet with the portable charger and a 20 foot extension cord but wondering if this is safe. There do seem to be such cords designed for Tesla.

First, if you're talking about a wall outlet, it's most likely 240v since the country went from a 110v grid to a 120v grid back in the 60s. But it's still called 220 just like a refrigerator is called an ice box. If you put a meter on it you'll see 240v.
More importantly, it's the current draw, not the voltage that's important.
I have a workshop with 240v 20A outlets. My charger is 240v 16A.
I am using an extension cord rated at 20A.
I measured its temperature and it gets up to 96 degrees.
Don't use a normal household extension cord. Use something that's rated for your current draw.

 

[nuMach]

the issue about cycled loads vs continuous.
dont know what the US code is, but in Canada feeder (supply) cables need to be rated at 125% of the actual load.

so 40A charge demand for the charger, you need 50A rated cable.
since 40A is a #8, and 60A is #6 ... at 40A load a #6 is well suited for a continuous load.

manufacturers have to adhere to the code as well, and cable lengths should reflect calculations for stated rating and voltage drop.

Of course theres the guy who will buy 2, and connect them to make a 100' cable ...but thats outside the manufacturers control.

For the original poster ... if considering a 14 gua extension cord to supply the charger - obviously a nogo. 6 gua cable go for it. 10kw generator will have to be really working to do the job, so using the chargers menus to select the next lowest rate will help the charger out, Of course a bigger generator (12-14k) will do it easily.

 

[KevinS]

Anyone purchasing a J1772 extension should be aware that 95% of them are only rated for 40 amps. Ones made by Tuscan EV are rated to 50. If you hard wired you should ensure you get the right extension.

The Ford mobile charger is only rated to 32A, so would that combo still be an issue since it's downstream of the charger?

Doesn't seem like it would be, but maybe I'm not considering something.

 

[DevSecOps]

The Ford mobile charger is only rated to 32A, so would that combo still be an issue since it's downstream of the charger?

Doesn't seem like it would be, but maybe I'm not considering something.

Nah it'll be fine. That's why I said those that hardwire. Any EVSE that plugs in will be fine as none of them will exceed an output of 40A. Hardwire units like the one for the lightning or chargepoint flex will exceed 40A in a hardwired configuration.

 

[KevinS]

Nah it'll be fine. That's why I said those that hardwire. Any EVSE that plugs in will be fine as none of them will exceed an output of 40A. Hardwire units like the one for the lightning or chargepoint flex will exceed 40A.

Cool - I have the Chargepoint on a 50A but downrated it to be at 32A for that reason (and I also think charging at a slower rate is better for the battery health.)

 

[nuMach]

can only speak about the Emporia as I have one .... it doesnt know if its plugged in or hardwired.
You set the config in the menus with the app.

So its conceivable someone could set it to 48A on a plugin connection. Theres nothing to hard limit it if its deliberately mis-configured. Its defaulted to 40A as it comes with a plug-in cord.

Once hardwired, you have to go into the menus and swear its hardwired.

For hardwired use, the cord is removed, and the hardwire connection uses the same lugs in the Emporia

Mines hardwired, and I left it at 40A as I have no time constraints when charging at home. Lower rate is easier on everything.

 

[bbulkow]

We have an emergency generator because we lose power 1-2 times a year and with Sandy years ago we were out for two weeks. The problem is the generator was installed before we had an EV and the EV plug is not on the panel that is powered by the generator. I could reach a powered 220v outlet with the portable charger and a 20 foot extension cord but wondering if this is safe. There do seem to be such cords designed for Tesla.

Extension cords are rated based on the gauge of the wire. The plug format tells you the amps the *plug* is rated for.

To code, all wires have, printed on the wire and every few feet, the rating of the wire. Sometimes it's hard to see, but it'll be there. They print is every few feet in case you can only see a few feet, or it gets rubbed off.

Figure out the amp load. This is usually determined by the "charger". Eg, if you're using a ford or tesla charger, it'll have some amount of amps it wants to pull at 220.

Since it's a continuous load, you'll want to make sure there is 20% headroom. Basically multiply the amps of load by 1.25.

Then, check the breaker you've got on the circuit. The breaker should be at that value or higher (which means the various wiring that's not an extension cord is built out to that code).

In terms of your extension cord, you can simply match the extension cord to the circuit max, or you can match the extension cord to the expected load. Matching to the circuit is better, matching to the expected load works fine as long as you're right. Read the wire, determine if you're safe.

Don't listen to "I wouldn't chance it". This is science. There is code. The wire has a rating. Look up the answer. Believe the answer.

If you don't trust your math, touch the cables and connectors after 10 minutes of charging. Warm is OK, hot is not. You should be able to hold it comfortably for a few seconds. ( If I was talking to an actual geek, I'd look up the common heat rating of a connector, I think they're usually 60C, and say pull out your IR thermo gun and check temp after 10 minutes )

 

[SWO]

Thank you for the explanation. That is very helpful. So even though the cord is rated for 50 amps you need to use it at a much lower amperage because its an EV. I would be using the MachE portable charger in these situations. Again, not really sold on one solution or the other although the J1772 cords seem to be about twice the price so for something that would get very infrequent use that might be a consideration.

I bought the 30ft 50A 14-50 RV extension cable. If you read the reviews on Amazon there's plenty of people using them for EVs without issue.

I get the logic some use for getting a J1772 extension and I looked at them, but they're all made by Lectron or no-name companies with dubious quality. Look at the Amazon reviews and you will see broken connectors, exposed insulation, etc.

Sponsored