A warning about 50A range cords...

[Mach-Lee]

I wanted to share my experience with a range cord that ended up being faulty. I had to mount my ChargePoint in a location where the included cord didn't quite reach the 14-50 outlet, so I bought a 50A range cord to use instead like others have done. I chose a GE (well-respected brand) model WX09X10037 cord, which is rated for 50A and is UL listed (again thinking that means it should be good quality). This cord has good reviews on Amazon, 4.7/5.0 with 329 ratings, and other reviewers have said they've used it successfully as an EVSE cord.

However after installation I noticed it would get quite warm while charging, up to 152ºF when my garage was only 70ºF! You can see the left side got quite a bit warmer than the right side, which indicates a bad connection:

I also noticed my charging speed would drop from 40A to 38A after about 15 minutes of charging:

At first I thought my receptacle could have a loose connection, so I took it out and loosened/torqued everything to specs again. Still got hot, so then I replaced the receptacle with a Bryant (clone of Hubbell) 9450FR industrial-grade receptacle, torqued to specs. Alas, it still got hot, so it had to be the plug not the receptacle. So I ordered a Bryant 9452ANPB industrial-grade plug to try instead.

There is a huge difference in construction of the Bryant plug vs. the GE. The blades are much thicker and solid brass, compared to the thin, folded over blades of the GE. The attachment lugs inside are also very robust, thick metal everywhere. The plug is expensive, but you are getting what you pay for.

After cutting the molded plug off the range cord and replacing with the Bryant plug, I can say there was a huge improvement in the plug heating! Testing the prong temperature, it barely gets warm now (100ºF) vs. the burning hot (152ºF) of the GE plug. Check your prong temps!

I did some additional testing on the GE plug, and found the internal resistance of the left and right prongs to be 8 and 4 mΩ, respectively. This is far above the 1.5 mΩ threshold for a safe connection at this current level. In contrast, the internal resistance of the Bryant prongs was less than 1 mΩ, excellent.

In conclusion, there is a poor internal connection between the prongs and the wires inside the molded range cord plug head. This creates an unsafe level of heating which may have caused the connection to weaken and eventually fail. Even though this product is UL listed, it is of inferior quality and would fail the UL 817 temperature test with greater than a 54ºF rise. Reading through reviews, others have reported the same hot plug issue with this cord after finding the same internal defects, so there seems to be a lot of variation in the quality of the internal connections, not good. Therefore, I do not recommend you buy this style of range cord! This 50A cord is also sold under other brands including GE, Southwire, HDX (Home Depot), Electrolux, and Smart Choice. The plug is marked E72389-F PHILIPPINES between the prongs for reference.

In addition, after replacing the plug I no longer notice the 2A drop in charging current, and I'm getting a solid 9.5 kW now. I did some investigating and it appears that the Mach-E (not the ChargePoint) dropped the charging amperage after noticing the increased voltage drop from the poor connection heating up. Yes the internal charger (SOBDM) monitors voltage drop and responds appropriately. If you see a drop in charging amps/power a few minutes after charging starts, it's probably a clue you have a bad connection heating up somewhere and you should investigate. Thermography is a great tool for finding hot connections, but feeling with your hands (safely) also works well. Anything with more than a 45ºF temp rise above ambient should be suspect.

No more problems, I strongly recommend going with the Bryant 9450FR NEMA 14-50 receptacle and the 9452ANPB plug if you want the most robust 14-50 connection possible.

 

[P. T. Magoo]

Thank you for this!

Is the thermography from an app, or do you have special tools for that?

Thanks again.

 

[BillPitman]

I wanted to share my experience with a range cord that ended up being faulty. I had to mount my ChargePoint in a location where the included cord didn't quite reach the 14-50 outlet, so I bought a 50A range cord to use instead like others have done. I chose a GE (well-respected brand) model WX09X10037 cord, which is rated for 50A and is UL listed (again thinking that means it should be good quality). This cord has good reviews on Amazon, 4.7/5.0 with 329 ratings, and other reviewers have said they've used it successfully as an EVSE cord.

However after installation I noticed it would get quite warm while charging, up to 152ºF when my garage was only 70ºF! You can see the left side got quite a bit warmer than the right side, which indicates a bad connection:

I also noticed my charging speed would drop from 40A to 38A after about 15 minutes of charging:

At first I thought my receptacle could have a loose connection, so I took it out and loosened/torqued everything to specs again. Still got hot, so then I replaced the receptacle with a Bryant (clone of Hubbell) 9450FR industrial-grade receptacle, torqued to specs. Alas, it still got hot, so it had to be the plug not the receptacle. So I ordered a Bryant 9452ANPB industrial-grade plug to try instead.

There is a huge difference in construction of the Bryant plug vs. the GE. The blades are much thicker and solid brass, compared to the thin, folded over blades of the GE. The attachment lugs inside are also very robust, thick metal everywhere. The plug is expensive, but you are getting what you pay for.

After cutting the molded plug off the range cord and replacing with the Bryant plug, I can say there was a huge improvement in the plug heating! Testing the prong temperature, it barely gets warm now (100ºF) vs. the burning hot (152ºF) of the GE plug. Check your prong temps!

I did some additional testing on the GE plug, and found the internal resistance of the left and right prongs to be 8 and 4 mΩ, respectively. This is far above the 1.5 mΩ threshold for a safe connection at this current level. In contrast, the internal resistance of the Bryant prongs was less than 1 mΩ, excellent.

In conclusion, there is a poor internal connection between the prongs and the wires inside the molded range cord plug head. This creates an unsafe level of heating which may have caused the connection to weaken and eventually fail. Even though this product is UL listed, it is of inferior quality and would fail the UL 817 temperature test with greater than a 54ºF rise. Reading through reviews, others have reported the same hot plug issue with this cord after finding the same internal defects, so there seems to be a lot of variation in the quality of the internal connections, not good. Therefore, I do not recommend you buy this style of range cord! This 50A cord is also sold under other brands including GE, Southwire, HDX (Home Depot), Electrolux, and Smart Choice. The plug is marked E72389-F PHILIPPINES between the prongs for reference.

In addition, after replacing the plug I no longer notice the 2A drop in charging current, and I'm getting a solid 9.5 kW now. I did some investigating and it appears that the Mach-E (not the ChargePoint) dropped the charging amperage after noticing the increased voltage drop from the poor connection heating up. Yes the internal charger (SOBDM) monitors voltage drop and responds appropriately. If you see a drop in charging amps/power a few minutes after charging starts, it's probably a clue you have a bad connection heating up somewhere and you should investigate. Thermography is a great tool for finding hot connections, but feeling with your hands (safely) also works well. Anything with more than a 45ºF temp rise above ambient should be suspect.

No more problems, I strongly recommend going with the Bryant 9450FR NEMA 14-50 receptacle and the 9452ANPB plug if you want the most robust 14-50 connection possible.

This reporting should be sent to UL and GE, inferior products…….Bill csg

 

[Nklem]

The issue is the GE range cord is for a “GE electric Range“, not an EV charger and they use no where close to 50 actual amps. They are not for a continuous full amp load like an EV charger. Maybe 30-40 Amps maximum. In theory it should work, but you made the correct call to buy an industrial plug rated for the true use. I would be weary of the wire as well. I bet with a 20% Electrical code de-rating, it is rated for 40 amps only.

 

[KlueBat]

Good stuff OP! Thank you for writing this up.

Thank you for this!

Is the thermography from an app, or do you have special tools for that?

Thanks again.

The image sensors on your phone are not tuned to pick up the IR spectrum, so you'll need a dedicated camera. If you see an "IR app" in the app store, its either fake or designed to work with an external IR camera. A quick search on Amazon tells me that IR cameras still are not cheap, but they are way cheaper than they were a few years ago. I might have to pick one up just for fun.

 

[Deleted member 3569]

Wrong application ... There is nothing wrong or any poor quality issues with the GE plug .... its for a generic electric range (20A breaker), not to be used for charging EV w/32A continuous current on a 50A breaker. I have used the very same plug (from HomeDepot) as replacement for my tenant's range frayed plug and it is fine .... besides by extending the suppied pigtail cord of your EVSE you just invalidated its warranty. If the EVSE comes with a NEMA 14-50 pigtail It is meant to be plugged into a hard wired solid copper 12 AWG socket with NEMA 14-50 outlet, protected by 50A breaker.

 

[Garbone]

That wire does appear a bit thin. In the 83.3 photo you can see it heating. Over time it will scorch and the internal resistance will rise. I would get something better or move the outlet closer to the charger.

 

[Mach-Lee]

The issue is the GE range cord is for a “GE electric Range“, not an EV charger and they use no where close to 50 actual amps. They are not for a continuous full amp load like an EV charger. Maybe 30-40 Amps maximum. In theory it should work, but you made the correct call to buy an industrial plug rated for the true use. I would be weary of the wire as well. I bet with a 20% Electrical code de-rating, it is rated for 40 amps only.

This is a common misconception. I read UL 817 which is the testing criteria for appliance cords. They must be tested at full rated current, so 50A in this case. I’m fairly confident the plug would have melted on this cord if subjected to the full 50A. Electrical devices must be tested to their full rated current and used at a derated current, otherwise there is no safety margin.

The application doesn’t matter, the cord should carry it’s full rated current continuously without overheating past the test specs (54°F rise in this case). If it can’t it’s junk.

Wire is fine and good quality (6ga), using at 40A is the appropriate derate on the wire. The wire gets equally or less warm than the J1772 cord in use.

 

[Mach-Lee]

Wrong application ... There is nothing wrong or any poor quality issues with the GE plug .... its for a generic electric range (20A breaker), not to be used for charging EV w/32A continuous current on a 50A breaker. I have used the very same plug (from HomeDepot) as replacement for my tenant's range frayed plug and it is fine .... besides by extending the suppied pigtail cord of your EVSE you just invalidated its warranty. If the EVSE comes with a NEMA 14-50 pigtail It is meant to be plugged into a hard wired solid copper 12 AWG socket with NEMA 14-50 outlet, protected by 50A breaker.

Electric ranges are 40A or 50A breakers, not 20A. See my above post. It should handle 40A continuous just fine if it’s a 50A rated cord.

The ChargePoint Home Flex may be used with a plug or hardwired per instructions.

 

[Mach-Lee]

Thank you for this!

Is the thermography from an app, or do you have special tools for that?

Thanks again.

It’s a FLIR ONE thermal camera.

 

[Mach-Lee]

That wire does appear a bit thin. In the 83.3 photo you can see it heating. Over time it will scorch and the internal resistance will rise. I would get something better or move the outlet closer to the charger.

The wire was only about 100°F in that photo, equal to my body heat reflection in the cover plate. The color scale dynamically adjusts to the warmest thing in the photo, so white in that thermograph is much cooler than white in the GE plug photo. The wires are 6 ga copper inside the cord, which is the correct size for a 50A rating.

 

[MachTee]

I bought a very similar 6' cord from Best Buy. It's not labeled GE but it looks near identical. Same with my Wallbox charger, the included 1' cord couldn't reach my 14-50 outlet so I had to lengthen it. Been using it for nearly a year now and I have no issues with it. Just a bit warm when it's charging even at 40A, though my default is 32A. Perhaps there's a faulty connection inside the connector.

If you feel like taking it apart, it'll be interesting to see if there is in fact a faulty connection inside the plug.

Edit: as you can see I tried to just use the cord that came with the Wallbox, marred up my wall and just couldn't make it work. Haven't patched it up yet lol.

 

[Mach-Lee]

I bought a very similar 6' cord from Best Buy. It's not labeled GE but it looks near identical. Same with my Wallbox charger, the included 1' cord couldn't reach my 14-50 outlet so I had to lengthen it. Been using it for nearly a year now and I have no issues with it. Just a bit warm when it's charging even at 40A, though my default is 32A. Perhaps there's a faulty connection inside the connector.

If you feel like taking it apart, it'll be interesting to see if there is in fact a faulty connection inside the plug.

Edit: as you can see I tried to just use the cord that came with the Wallbox, marred up my wall and just couldn't make it work. Haven't patched it up yet lol.

I'd like to take it apart, but I don't think I'll be able to without completely destroying it and the evidence. The connections are molded into the plug head.

The thing I've learned about this cord is the connection quality is really variable from unit to unit, you don't know what you're going to get. I got a worse one, you might have gotten a better one. If you grab the cord in the middle after charging an hour, it should be about the same temp as the plug head. If the plug feels warmer, stop the car charging, unplug it, feel the prongs. They should be warm but not burning hot. If it hurts to touch then it's too warm. The problem with overheating is it will slowly degrade the connection further with time. Annealing will cause the receptacle and prong crimp to lose their spring tension, and pyrolysis will degrade the thermoplastic materials until they crack or weaken. Keep an eye on it.

After the upgrades my plug and cords all get equally warm now, around 100ºF in use.

 

[Maquis]

It should be noted that ranges are not considered continuous loads. In the real world, no one ever has all burners on full while self-cleaning the oven for 3+ hours!

Plus, the GE consumer brand has been sold off. Things sold under that brand are not from the industrial GE we all knew and loved 40 years ago.

 

[JCHLi]

The issue is the GE range cord is for a “GE electric Range“, not an EV charger and they use no where close to 50 actual amps. They are not for a continuous full amp load like an EV charger. Maybe 30-40 Amps maximum. In theory it should work, but you made the correct call to buy an industrial plug rated for the true use. I would be weary of the wire as well. I bet with a 20% Electrical code de-rating, it is rated for 40 amps only.

I would think any plug that plugs into a 14-50 outlet would need to be rated for 50 amps. Kind of the whole point of having a specific plug shape for different amperages.

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