Wire gauge for makeshift 16A L2 EVSE power cord?

[CZroe]

Since being displaced by a tornado my brother has no good place to charge his Chevy Volt. My car was crushed by the same tornado so we’ve been sharing his car.

I’ve been using a EVSE at the rented workshop where I now sleep but I lose electric range when I bring him the car every morning. It would be great if we could occasionally top it off at the place where he is renting a room. Any more than that would probably be an issue since it isn’t his power bill.

There is an old, disused, dryer plug nearby where I can easily tap 240v. His car charges at a maximum of 12A but the portable EVSE control board I bought can deliver up to 16A with other cars. It seems to be a GM spare and exactly the same ClipperCreek “Gen2” control board used in the portable EVSE included with the Chevy Bolt and later Volts.

The control board only set me back $30 and a used 22.5’ cable with J1772 Type 1 J-plug was another $51. I got a cheap waterproof enclosure and I planned to reuse some monster 10-gauge 600v appliance cord from my workshop heater I no longer need.

Unfortunately, that cord is much too thick… nearly an inch diameter. Much thicker than the J-plug’s cable which is just over half an inch. Even that will be a tight fit for my largest water-tight cable gland where I somehow need to squeeze a 0.535” cable into a fitting for up to 0.51” diameter. To get power into the enclosure I’m hoping I can get away with smaller and much more affordable 12-gauge 300v appliance cord.

Like most appliance cord it is stranded with rubber insulation. I’ll be using ferrules at either end for a better connection. Will 12-gauge stranded be enough to carry 12 to 16A over two 120v hots with a ground?

When I look this up I see charts and voltages where I don’t know how it applies to having two 120v hots for 240v versus one hot and a neutral. Do I consider this 16A 240v or 8A 120v for each conductor?

[bdunham7]

Will 12-gauge stranded be enough to carry 12 to 16A over two 120v hots with a ground?

When I look this up I see charts and voltages where I don’t know how it applies to having two 120v hots for 240v versus one hot and a neutral. Do I consider this 16A 240v or 8A 120v for each conductor?

Yes, 12 AWG is sufficient for charging a Volt.  16A @ 240V is 16 amps on each 'hot' conductor and none on the neutral.

[wizard69]

12 AWG will handle 16 amps.    However if you are contemplating a long extension you should consider voltage drop which ideally should be under 2%.

Your potential bigger problem is that the dryer plug most likely is not  properly protected for a 12 AWG cord.  That is it most likely will be a 30 amp circuit which implies #10 wire.  This is a huge problem because it is easy to damage an extension cord in a way that can lead to heating.

As for the cord gland, buy one that properly grips the cord.   I'm not sure why you need one for an extension cord, you do not want to be using extension cord wire in a permanent installation.  Which brings up the question if you already have a 10 AWG cord why not buy a plug to put on it that is proper for the dryer outlet?

[SeanB]

Quick soloution for long cable is simply to get 2 waterproof boxes and glands, one side for the 10 gauge wire, other side for the 12 gauge, and put 3 feet of 12 gauge on the end  of the heavy wire, with a drier plug at one end, and a inline drier socket at the other, unless you are wiring the EVSE direct into the outside junction box.

[CZroe]

I’ve been collecting it all together. Progress so far:
https://imgur.com/a/dyRXAeF

Yes, 12 AWG is sufficient for charging a Volt.  16A @ 240V is 16 amps on each 'hot' conductor and none on the neutral.

Exactly what I needed to know. Thank you very much!

12 AWG will handle 16 amps.    However if you are contemplating a long extension you should consider voltage drop which ideally should be under 2%.

Thanks. It will not be an extension. “Appliance cord” is just what Lowe’s calls the round, flexible, stranded cord they sell by the foot or on rolls. This heater uses 600v 10-gauge appliance cord because it was strangely cheaper by the foot than the 300v kind:


The J1772 standard says the EVSE cord should not be more than 30cm~1’ to the outlet. We won’t even be using an outlet at this place (temporarily hard-wired like the heater) but I will keep the leads around that length for eventual use as a portable EVSE with a water-tight plug.

Your potential bigger problem is that the dryer plug most likely is not  properly protected for a 12 AWG cord.  That is it most likely will be a 30 amp circuit which implies #10 wire.  This is a huge problem because it is easy to damage an extension cord in a way that can lead to heating.

I’d planned to bypass the dryer outlet since the outlet’s housing was missing with exposed contacts. Unfortunately, I just got another look and it seems the existing wiring is missing too:


There’s literally nothing there I can use. Yeah, this place got hit by the tornado too and is still a huge mess. It looks like the wiring was moved to a 4.6A hot water pump on a 30A breaker but there is an unused 40A breaker in the box. Thankfully I have a scrap of 10-3 Romex, some fittings, wire nuts, and a 4” junction box left over from another job:


The other end of the appliance cord will be soldered directly to the EVSE control board exactly like the original General Motors product except I won’t have a molded plug with thermistor. The J1772 plug/cable at the other end of the EVSE is plenty long enough so I will not need to go over 30cm with the appliance cord.

As for the cord gland, buy one that properly grips the cord.   I'm not sure why you need one for an extension cord, you do not want to be using extension cord wire in a permanent installation.  Which brings up the question if you already have a 10 AWG cord why not buy a plug to put on it that is proper for the dryer outlet?

The idea is to use it with a portable water-tight enclosure but hard-wire it like a wall charger until he can move to a better place. At that point I will give it an appropriate water-tight plug for use as a portable dual-voltage EVSE exactly like the GM unit the board was intended for. No extension cords for either scenario.

The control board I ordered (actually paid $30):


The enclosure I ordered:


The enclosure the control board was designed for:


Here is someone’s OpenEVSE build using what appears to be the same enclosure I ordered:
https://youtu.be/to4eYCJ4ZfM

It looks like he also used appliance cord and water-tight cable glands.

Since the enclosure I bought is stuck in Shanghai’s lockdown right now I’m going to order some PG 16 and PG 13.5 glands that should fit the cables perfectly but I’m trying to stay under the cost of simply buying another portable EVSE and a tighter fit, if possible, would’ve saved me money.

The GM version of the portable EVSE with this same ClipperCreek control board has a molded NEMA 5-15P with thermistor but works at 120 or 240v (Level 1/2). The AmazingE version I’m using at the workshop has the exact same ClipperCreek control board paired with a molded NEMA 14-30P, no neutral connection, and no thermistor. It is supposed to be a portable unit so I’m tempted to hack that unused neutral prong off to fit NEMA 14-50 receptacles without an adapter.

Despite having the same control board, the AmazingE only seems to work at 240v (Level 2). People have tried 120v but it’s either limited by microcontroller programming or refusing to work at 120v without the thermistor:
https://youtu.be/ydFKV3zJMzA

The new control board I got for this project appears to be the dual-voltage GM version. According to the stickers on the microcontroller, GM seems to use “LVGM33A” firmware/programming while AmazingE uses “LVGM33F.”

Despite this new board being made two years after the AmazingE, it has the same version sticker on the micro that I see on dual-voltage GM units from six years ago. The new board also has glue on the through-hole components… like GM. All AC components are rated for 250v and I’m reasonably sure it is a GM spare or equivalent.

I don’t have access to an assembled GM version to measure/bypass the thermistor so I hope it doesn’t require one.