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Using a Prius Prime custom cable setup with my MY -- temporary

jjs357

Member
Jan 1, 2021
6
1
Bryn Mawr PA
I traded in a 2020 Prius Prime Limited for a Model Y. I had a Prius forum member make a custom cable pigtail that plugged into my NEMA 14-50 50A 240V receptacle and ended in a 5-15 socket. The two blades in the plug were wired to the two sides of the socket providing 240V. This worked because the Prius Prime charging circuitry was dual voltage aware.

The pigtail plug end is a little more flexible and plugs into my outdoor receptacle. I bought a true 14-50 extension cord to use with the MY but the cable is so stiff I don't have clearance to plug into the socket. If I use the 5-15 socket and a heavy extension cord with ordinary 120V plug and socket ends, I was able to get 240V to the Prius charger. Can I use the Tesla Mobile Charger with the 5-15 dongle that comes with the mobile charger and plug this into the socket end of my extension cord, and the plug end of the extension into the socket end of my custom 240V cable adapter?

Will the Tesla charging electronics sense the 240V nature of the connected wire even when I am not using the official 240V 14-50 Tesla dongle. I bought one of these already but the Tesla mobile charger cable is too short to reach from my townhome parking place to my patio where the receptacle is located.

I am having an electrician come to fix the outside receptacle box so the standard extension works but in the meantime I was hoping to get faster at-home charging.

This is a weird setup and I don't want to damage the Tesla charger. But I have 240V/50A available but the extension cord I bought won't work currently because the cable is too thick. This older setup worked for the Prius that only has a 5-15 plug on it's mobile charger.
 

user212_nr

Active Member
Aug 26, 2019
1,407
873
US
Yes, it will charge at 240v, 12A.

The plug does not contribute anything with regard to voltage, only to amperage.

I am having an electrician come to fix the outside receptacle box so the standard extension works but in the meantime I was hoping to get faster at-home charging.

I have 240V/50A available but the extension cord I bought won't work currently because the cable is too thick. This older setup worked for the Prius that only has a 5-15 plug on it's mobile charger.

This doesn't make a lot of sense. Too thick, for what? What is a "standard extension"?

I take it that you have some obstacle like a badly placed outlet box, but that's a stretch of the imagination.
 
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jstjohnz

Member
Sep 7, 2020
102
59
Indianapolis
I would be curious also to no what exactly the issue is with the existing 14-50 receptacle. Maybe an in use cover that's nor oriented correctly? Not exactly fast charging with this arrangement but better than 120V.
 

user212_nr

Active Member
Aug 26, 2019
1,407
873
US
The pigtail plug end is a little more flexible and plugs into my outdoor receptacle. I bought a true 14-50 extension cord to use with the MY but the cable is so stiff I don't have clearance to plug into the socket.

See this now, post was long so I missed this part. Its still a very unique problem, usually there is a lot of clearance.
 

jjs357

Member
Jan 1, 2021
6
1
Bryn Mawr PA
Thanks for the replies. OP here. The lip on the outlet enclosure goes all the way around. There was no cut-out for the downward facing extension cord at the bottom. I managed with my Prius because the pigtail I got specially made to get 240V to the Prius was not as thick and stiff.

However my problem was remediated with this (see attached image) Screen Shot 2021-01-08 at 2.30.14 PM.png

This fit into the socket and then the extension cord had clearance to descend down past the outlet enclosure.

So I was able to get the extension cord to where the Tesla Mobile Charger could plug in and then reach my car. I got the expected charging rate of 32A and the voltage, as shown by the Tesla app, was around 237V. Replenished charge at about 30 Miles an hour, which is what I expected.
 
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user212_nr

Active Member
Aug 26, 2019
1,407
873
US
Thanks for the replies. OP here. The lip on the outlet enclosure goes all the way around. There was no cut-out for the downward facing extension cord at the bottom. I managed with my Prius because the pigtail I got specially made to get 240V to the Prius was not as thick and stiff.

However my problem was remediated with this (see attached image)View attachment 625752

This fit into the socket and then the extension cord had clearance to descend down past the outlet enclosure.

So I was able to get the extension cord to where the Tesla Mobile Charger could plug in and then reach my car. I got the expected charging rate of 32A and the voltage, as shown by the Tesla app, was around 237V. Replenished charge at about 30 Miles an hour, which is what I expected.

People have had a lot of problems with 14-50 outlets melting. Hard to say how many, but if your setup is at all "loose" it is a problem.

The effect of gravity will cause it to loosen (and then melt). Supporting the cable could help.
 

jjs357

Member
Jan 1, 2021
6
1
Bryn Mawr PA
I know that plugging and unplugging from a 14-50 outlet is a potential problem. I have no choice as I am not in a garage/protected area but rather have the outlet (professionally installed) on a brick patio wall. I plug in when I want to charge. The extension does not have far to travel until it meets the patio floor. So supporting it does not seem likely to be necessary. I route the heavy duty 240V extension cable to where I connect the mobile charger with the 14-50 adapter. For now I am leaving the adapter piece connected to the extension. Then I plug into the charger brick and the charger end into the car.

So far, I have only done one session like this but this is my normal method of at-home charging going forward.

I will check for heat and looseness, especially as temperatures get warmer. Located in Philly suburbs so things are cold now. I may have the electrician come back to check in the Spring or if I notice "loose" connections.

Good to know that I need to be careful. I am in a townhome complex and this is the best I can do.
 

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