Prime Plug-in Charging Fix

I don't believe this is the case. The National Electrical Code specifies:

(A) Receptacles. Receptacles shall be listed and marked with the manufacturer’s name or identification and voltage and ampere ratings.

(B) Rating. Receptacles and cord connectors shall be rated not less than 15 amperes, 125 volts, or 15 amperes, 250 volts,
and shall be of a type not suitable for use as lampholders.

I went to the garage and looked at my spare outlets and plugs, and all the NEMA 5-15 configuration are listed for 15 amp.

You may be referring to current de-rate on extension cords over certain lengths.

This would indicate a problem with these individual circuits. Perhaps the terminal lugs are loose, among other potential problems.

I charge my Prime every day at 12 amps on a 14 AWG branch circuit, protected by a 15 amp breaker, with NEMA 5-15 plugs and receptacles rated at 15 amps and have no problems.

 

This x1000.

New NEMA 5-15 installed properly in proper circuits should be fine up to 15amps. Then you have to take people and nature into the mix, which can both reduce the actual current it can handle. This is why engineers often add a hefty safety factor into any design. I personally went with a 20amp/120V dedicated circuit setup for my home charging system for just this very reason.

 

How are people involved in this - damaging the plugs? If nothing is damaged in the plug or receptacle, once you plug them together the human is out of the loop.

 

NEMA 15-amp devices are rated for 15 amps. That being said, one usually designs circuits with a safety factor of 20%, so that may be what you're interpreting as a 12-amp rating.

In actual practice, connectors are subject to all kinds of wear and tear -- and abuse. A thin layer of corrosion on the prongs of a plug or outlet will provide electrical resistance and result in possible overheating. Similarly, a worn outlet may not make firm contact with the plug, thus reducing the contact area through which current must flow. Again, possible overheating.

And, finally, there are considerable differences in manufacturing quality of similar wiring devices. Those 49-cent Home Depot no-brand outlets are no comparison to a more expensive Leviton, Legrand, or Pass & Seymour wiring device.

I did not know that the component of the Prime's OEM charging cable could be ordered separately. Good to know.

However, be aware that the "brick" is a weather-proof housing designed for wet and outdoor use. The places where the cables enter and leave the housing must be water-tight or you could find yourself in a very dangerous situation. For example, with the brick laying in a rain puddle, on a damp floor, or in snow.

 

A standard 15A receptacle is fine for charging, but it's not designed to withstand plugging and unplugging everyday. The wiring book I have recommends hospital grade receptacles for EV charging. For example:
Leviton 15 Amp Hospital Grade Extra Heavy Duty Self Grounding Duplex Outlet, White-8200-W - The Home Depot
Leviton 20-Amp Hospital Grade Extra Heavy Duty Self Grounding Duplex Outlet, White-8300-HW - The Home Depot
Leviton 20 Amp Self-Test SmartLockPro Hospital Grade Duplex GFCI Outlet with LED, White-072-GFNT2-HGW - The Home Depot
Leviton 15 Amp SmartlockPro Extra-Heavy Duty Hospital Grade Tamper-Resistant Duplex Self-Test GFCI Outlet, White-GFTR1-HGW - The Home Depot

Don't use a 20A receptacle on a 15A circuit. And it is recommended that the circuit used for charging be GFCI protected, either at the breaker or at the receptacle, in addition to the GFCI built into the EVSE brick.

 

Since the outlet used for charging is likely outdoors or in a garage, it is more than a recommendation, it is a requirement by the NEC. Among other likely to be wet locations (bathrooms, kitchens, sinks), GFCI are required by Article 210.8 in the following locations likely to be used for PHEV charging:

(2) Garages, and also accessory buildings that have a floor located at or below grade level not intended as habitable rooms and limited to storage areas, work areas, and areas of similar use

(3) Outdoors

(4) Crawl spaces — at or below grade level

(5) Unfinished portions or areas of the basement not intended as habitable rooms

(10) Laundry areas