How you charge your car?

Why? Because that warning is there to protect against people who have no idea about why extension cords can cause problems or be dangerous.

I have more than a little experience with and knowledge of electricity. When they tell you not to use an extension cord with all sorts of different devices, they are giving a warning to cover the most uninformed among us. There is absolutely nothing wrong with using an extension cord as long as: (1) the overall run between the circuit panel (or subpanel) and the device ultimately being plugged in is not longer than what code would allow and (2) the cord is of sufficient gauge and is grounded (grounded is necessary if the device being plugged in requires grounding).

The standard outlets in a house are mostly 15 amp, except for ones in the kitchen, bathrooms and maybe the garage. I have a few 20 amp outlets that I installed in my garage that are literally 2 feet from my circuit panel. The run of 12/2 wire to them is less than 4'. Twelve gauge solid wire (the type of wire in the cabling you run in a house) can carry 20 amps at up to 50' or 15 amps at up to 100'. So, if you don't have a very long run from your panel to the outlet you're plugging into, there's absolutely no reason that you can't use an extension cord. The electricity doesn't behave differently in an extension cord as opposed to the cabling in the wall (except that the stranded wire in extension cords can't carry quite as much amperage as far as the solid wire in cabling).

The real danger with extension cords, however, is when someone uses a cord with too-small a wire gauge to carry the load that's on it. It will heat up and could start a fire. If you're using a 12 gauge cord and keep it at 25' or under, you should be fine. If you use a 10 gauge, you're really fine. There's nothing inherently dangerous about extension cords. You just have to be mindful of their gauge and the amount of load you're putting on them. Stranded wire cannot carry as much amperage as solid cable, which is why I sometimes use a 15' 10 gauge extension cord with heavy motorized loads.

Wire is not some magical, unknown factor. If you use a heavy-gauge extension cord that isn't too long and it works, you're fine. If you're really concerned, use a meter to test the voltage at the end of the run where you'd plug your charger in. That will tell you if the voltage drop is too much for the charger to function properly.

 

You seem very focused on voltage drop for some reason, which I find interesting because it’s real but not particularly important in this application. I’m also not convinced you fully understand it.

I say this not to be snarky but because what you describe is not a voltage drop test. Voltage drop is a calculation, not a measurement. Indeed it requires the measurement you mention, under no load, plus a 2nd measurement under expected working circuit load, and then a math formula to compare the measurements to convert the numbers to a percentage of drop.

Furthermore if you really want to know how much drop the extension cord itself is creating, the test and calculation needs to be repeated a second time with the cord eliminated from the circuit, and the results compared. Otherwise you have no idea if the calculated drop is occurring due to the cord, or due to another wiring issue behind the walls, or both combined.

My main point? Sticking a meter in at the end of an extension cord, with no load, tells you absolutely nothing about voltage drop that occurs due to the introduction of an extension cord. That’s only one of 4 readings and 2 math calculations required required to get the answer.

This clip is British and 220v, and no extension cords involved, but the theory is sound to partially illustrate what I mean:


Voltage drop Is important for electric motors...too much drop causes motors to burn out. But our solid state charge controllers are certainly far more tolerant of some voltage drop, so I’m not convinced it’s much of an issue even if substantial drop exists. Most solid state devices have a wide operating range and can easily tolerate lower voltages. If voltage gets too low they just shut off and/or don’t function, but no harm is done. Even though there is a sticker on the Honda charger that it needs input of 110 to 120v, we know from others here that it functions fine with as much as 240v! So it wouldn’t surprise me if it continues to function fine even with lower voltages...80? Total guess. But many electrical devices have huge tolerance for voltage swings, making minor surges and voltage drops non-issues.

Heck, I charged my car once with 3 16 gauge extension cords plugged into each other end to end. They got pretty dang warm...I monitored them. Almost too hot to touch but didn’t melt. I assure you the voltage drop was very substantial though I didn’t measure it. But the charger didn’t care and the car charged fully. My only concern was heat buildup and I watched it closely while drinking beer with my brother out of morbid curiosity frankly waiting for a cord to melt and spark. I don’t suggest this, and I respect the danger, but indeed it worked.

The only reason we need heavy gauge extension cords is to ensure that Resistance doesn’t cause heat to build up too much to melt the cord and cause arcing, which could cause fire. Voltage drop is a very minor concern.

 

Thanks for clarifying that. I focused on voltage drop because it is one of the two things I know can be a problem as far as damaging whatever is plugged into the cord. My understanding is and has been that voltage drop itself is not a safety issue. Are you saying that voltage drop could not damage a car charger? That's it's just a matter of whether it works or not, and, if it works (if it charges), there is no risk of the lower voltage damaging the charger?

The only dangerous use of an extension cord I've ever encountered was a woman who was running a large window air conditioning unit that she had plugged into one of those old brown indoor extension cords. She had broken the ground prong off and taped the extension cord to the floor using duct tape. It was melting the tape and insulation, and I'm sure it was not doing the air conditioner any good, either (though it continued to work for years with a new cord of the appropriate size).

I just consider how much of a load whatever I'm plugging in creates. If it's my Black and Decker weed trimmer, I'll use a 50' 14/2 extension cord with no concern. If it's a high-powered microwave (one of the highest loads I have), like the one I have in my garage, I use a heavy-duty short cable (in that case a 5' 12/2). I'm guessing the owner's manual to the microwave says not to use extension cords, but I'm not the least bit worried about using a 5' 12/2 cord with it.

 

That makes at least 3 of us. While not an IBEW member, I have more than 35 years experience providing and working with temporary power distribution in the entertainment industry. I’ve seen a few electrical fires and countless melt downs.

I’m simply not willing to suggest the there is “absolutely nothing wrong” or that someone will be “fine” or “very fine” using an extension cord “as long as” and “if” certain conditions are met.

 

That’s my belief. Have not tested it. But that’s how almost all electronics with no motors work during brownouts, etc....they just shut down, or display an error message, or whatever. But no damage done. Only things with motors suffer damage from brownouts...things like refrigerators and air conditioners. The motors labor and overheat burning windings and such.

 

I’m willing!

Follow the rules, extension cord charging will be just fine! Break a rule? Might not be fine! Everyone at their own risk!

 

The charger is designed to handle a wide range of voltages, and the J1772 standard doesn't even communicate voltage to the charger, only amperage. The same pins on the J1772 connector are used for all AC charging - whether that is 120, 208, 240 or a "browned out" or over current from any of those. Don't know the exact specs for the charger Honda uses, but typical input voltage range is something like 90-264 Vac.

As to the EVSE (or charge cord) it is basically a relay controlled by a circuit board. Unlikely that a voltage drop will harm the board (and EVSE), but I guess it is possible (it would be a very poor design).

 

Well, I have to ask, what do you think is the problem with an extension cord of a sufficient gauge? Do you think the electricity knows it is passing from wall cable to an extension cord? It makes no difference to the transmission of the electricity.

There are other reasons and situations where you don't want to use extension cords. I saw a documentary in which a grandmother used an extension cord to run a Fry Daddy on a kitchen table (it is a deep fryer filled with hot oil). The Fry Daddy had a very short cord to facilitate it's use on kitchen countertops. While this grandmother was frying, her three-year-old grandchild walked by, tripped on the extension cord and the hot oil poured all over him. He is horribly disfigured for life.

As long as you employ common sense with extension cords, you are perfectly fine using them. Wire is wire.

 

@Insighter if you like playing with multi meter: Grab an object with a motor (tools are best...circular saw, good sized compressor, or similar is ideal), and plug it into an outlet. Plug your multi meter in the adjacent outlet. Click on the tool and see how much voltage drops during motor startup. I think you'll be surprised.

I just did this experiment with an old radial arm saw in my workshop just for the heck of it to remind myself how much things can change at the flip of a switch. 118.5V at rest, upon flipping the switch my meter instantaneously went down to 101 volts as the motor started up, and once the saw blade reached full speed the voltage settled at about 117.5V. So my voltage drop of this 13 amp motor running on that circuit was less than 1% (1 volt dropped divided by 118.5). However the surge at startup resulted in a nearly 15% voltage drop. But it lasts for less than a second. It's that massive startup voltage drop that is an issue which can cause a lot of heat buildup in a motor during that startup, if it takes too long...and possibly preventing startup and burning out the motor if the conductor can't carry the massive extra amp load that momentarily goes through the conductors. It's not uncommon for a 20 amp circuit to see a very quick 40 amp draw when some of these motors try to spool up. In a healthy circuit and motor it lasts less than a second, amp draw immediately goes down as fast as it came up, and the motor runs. But if too much resistance is in the wire or a connection, this voltage drop lasts too long and therefore the breaker trips. Or the motor never gets enough power to start spinning and it burns itself out without the breaker tripping. But most breakers can take a short surge such as this without tripping, if the circuit is healthy. Add in a super long thin gauge extension cord to your experiment, and voltage drop will be greater, last longer, and therefore your risk of tripping the breaker, or having a motor just humming but incapable of starting, is higher.

Now...back to Clarity. When I plug my Clarity into my Mustart EVSE which displays output digitally, it is very obvious that the car's charger is programmed to prevent any such start-up voltage drop load, by ramping up the load slowly. It probably takes a solid 5 seconds or more after plugging the car in for the amperage output to very gradually count up from zero to 30 amp charge rate. Clearly this is the result of the programming of the solid state charger in the car, thus preventing the huge instantaneous power surge like you see when you flip the switch of a power saw motor and dump the entire barrel of amps into the stationary motor all at one time...

 

Yes. This is well documented.

Who’s rules? Yours or Honda’s?

 

Last time I checked, electricity was incapable of conscious thought.

Every splice, terminal or connection creates an increased potential for a problem. Particularly one where 3 prongs are being shoved into slots.

An extension cord is temporarily power. It is connected and disconnected, wound up, twisted, thrown on the floor, driven over, pinched in doors, you name it. It isn’t secured inside your walls, exposed to stress or fatigue and it is rarely touched by human hands. All the connections in a home can actually be inspected. Try inspecting the connections on that heavy duty store bought extension cord. Unless you’ve made your own out of 12/3 and Hubbell plugs, it won’t be possible.

Now I must ask. When you used that heavy duty 12/2 extension cord with your microwave, did you use a ground lift adapter or cut off the ground pin on the microwave cord?

 

Obviously electricity is incapable of thought. My point, as I clarified, was that there is no detriment to the electricity going through an extension cord as compared to in-wall cabling.

As for your question, no, I would never break off a ground prong. I really don't know why you'd even ask that. I also didn't practice my lassoing skills with it or let a dog gnaw on it! I don't throw my extension cords on the floor. I don't drive over them. I don't pinch them in doors. Just like any cord that carries electricity or a signal, I am careful with them.

Your point about twisting of extension cords is irrelevant. There is already a cord on the included charger that carries AC and can be damaged. It is subject to all the same perils you describe! Obviously I know enough not to damage cords or to fix or replace them when they are damaged. That's pretty basic knowledge, and would be applicable to the use of all electrical cords in all situations. Are you now against the use of extension cords in all situations?

Three-pronged plugs that plug into outlets are not dangerous. Every outlet that has cabling run to it is created to have a plug plugged into it. More specifically, three-pronged plugs on extension cords are not any more dangerous than the three-pronged plug that is built into the included charger. The fact that you're adding an extra plug is of no practical consequence. I'm not familiar with "shoving" plugs into slots. I push them in.

The cord from the included charger's block to the car can also be damaged. What of it? Be careful and don't damage cords or they will quit working! Again, basic knowledge.

I am not afraid of electricity. I am competent to use extension cords where needed, and to understand why manufacturers often recommend against them even though they can be used safely. Why do you want to be combative here?

 

Neither really...the rules of electricity!

 

I just had to use extension cord with oem charger. After some time both connectors on that cord became very hot. Not cable itself, only connectors.
However connector on the oem evse was still cold.
I have to have an extension cord here at the RV park, so my next little project will be to get some high quality connectors and cable and assemble a good extension cord.

 

Combative?

I answered your questions. Now I’m done.

Farewell.

 

RV parks frequently have questionable power and improperly wired outlets. Have you checked the voltage or used a circuit tester on the outlet?

 

I’ve used extension cords before. The weak point seems to be the plug ends. A 12 gauge works great or even 14 gauge is heavy enough but most cords have crappy ends. I invested in heavy duty ones for about $10-$15 each. Get the best ones on the shelf at your favorite home improvement store.
I drive 80-100 miles a day on 120V and a tank of gas a week. With the size of the battery pack and your driving habits there is very little benefit to invest in a home level 2 charger. Simply being able to charge in 2 hours is nice but unnecessary. Future proofing is a good thing but you can probably always add a level 2 EVSE in the future just as easy as now.


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I’ve never had a problem with L1 it just takes a long time. In some ways it’s easier to control. It takes 2 hours to charge 15% not 22 or 46, etc minutes so I can do some basic math and time my charge for a particular SOC easily. If my estimate is off by an hour I’m still within 7% of my desired SOC.


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I know it’s counterintuitive, but I’ve been led to believe stranded wire can actually handle more current than solid wire of the same gauge.

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Efficiency is another concern. Voltage loss typically means there is excess resistance which creates heat instead of kinetic energy with you in your car. It’s not dramatic but after hundreds or thousands of charges I’m sure it makes up for more than the price of a good cord.


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