Longer cord

You mean something like this?:

It seems like a very expensive way to get around a using an outdoor rated 12 awg extension cord which can also be repurposed. Many of these are not weather and/or rain proof either much like trying to lengthen the cord between the J1772 connector and the controller. The only positive I see for these is it'll keep your EVSE from being stolen if this is the only thing protruding. Also there are 25' EVSEs that can be had for cheaper than this as well such as this Schumacher (actually 28') and you would have redundancy:

FYI: 25 feet is the longest output cable that can be provided for a charging station (EVSE) according to National Electric Code (section 625).

 

@Gooner with 2 posts so far at writing time.
where's the beef? want 15 more feet on your EVSE?
go to https://www.openevse.com/ and ask them how much.
I hope you wouldn't be too surprised at how much much it will cost you !!!

on a side note; check out how an electrician gets a tesla owner charging at a rate of $1 / 100 miles as an introductory rate from their utility in Indiana. I wish I lived their..... well maybe - maybe not - after expiration of the intro.
youtu.be/JsYefGUCxDM

 

You don't need a new EVSE.

Buy an extension cord that it is no thinner than 10 AWG and waterproof. 12 AWG and thinner will result in too much voltage drop and increase the charging time and create a safety hazard. Likewise, nonwaterproof cables will result in a safety hazard including risk of electrocution.

 

you can replace the cord with a longer one, but it is fairly complicated. and of course, you'd have to measure voltage loss

 

Gooner, it is more than a cord. The charger is inside the car. The brick on the charge cable is a smart power supply. The cord between the brick and the car is a 4 conductor cord with both the charging power and communication between the car's charger and the brick power supply. Even splicing in a new cord between the brick and the plug is fraught. The plug is said to contain an overheat protection device. I looked at mine...I can't read the print on that piece of cord to see the specs...how many conductors and what gauge. Probably the best low cost solution is to get a weather proof cover for the plug and add a 15' 12-3 extension cord.

 

I would say 10 AWG as I wrote above to minimize the voltage drop and resistive heating and an outdoor type because it will be used in a garage, which can get wet. This is "Amazon's choice" for 10-AWG outdoor extension cords. It is high-quality and affordable.

 

More is better, but...
10/3 portable cord has a rated ampacity of 30 amps.
12/3 portable cord has a rated ampacity of 25 amps.
The Prime charger draws 12 amps.
The Prime owner's manual recommends a 15 amp circuit.
14/3 portable cord has a rated ampacity of 18 amps.

I'd be happy with a 15' or 25' outdoor 12/3 cord.

 

Ampere capacity and voltage drop are different things. That is not how you choose AWG.

I took a course on illumination when I was an EE undergrad. That wasn't the best course I took, but the main thing the professor taught us was how to choose AWG for building wiring based on the ampere requirement and length of the wire to limit the voltage drop to a certain value. (When calculating the voltage drop, don't forget the drop along the return wire.)

• For 10 AWG, your voltage drop will be 0.20 V/A/100 ft. For 12 A, this is 2.4 V/100 ft.
• For 12 AWG, your voltage drop will be 0.32 V/A/100 ft. For 12 A, this is 3.8 V/100 ft.
• For 14 AWG, your voltage drop will be 0.50 V/A/100 ft. For 12 A, this is 6.0 V/100 ft.

The more the voltage drop, the longer the charging time and the higher your electric bill will be.

While for a 15-ft cable the voltage drop is small, I would still go with 10 AWG even for that length. As an added bonus, there will be less heating on the cable. The latter is more important if the cable is coiled, which could further increase the temperature of the cable and reduce the ampere rating due to poor heat flow.

 

Fwiw, by law, I was required to post the following:

 

LOL I didn't know about that movie.

It was the easiest course in my undergrad, and we didn't think much of it. The professor told us that we could draw wiring plans and make some money. I thought we hardly learned anything other than calculating the voltage drop. However, a friend of mine who took it with me told me that he built up on his knowledge to partner a company that installed electric systems in large buildings that became successful.