Charging rate suddenly dropped

[Jimmy T]

Hi I have a Nema 1450 outlet attached to my panel on a 40 watt breaker that usually puts out a decent charge for my model X. I typically get 15 miles per hour but recently it dropped to 7 miles per hour consistently but nothing else in the house is running (no AC's, etc).

I use a Camco 10 foot extension cord which I removed to test charging with just the cable that came out the car and it's the same rate.

Any ideas on what could be causing the sudden slow down?

 

[Jimmy T]

Hi I have a Nema 1450 outlet attached to my panel on a 40 watt breaker that usually puts out a decent charge for my model X. I typically get 15 miles per hour but recently it dropped to 7 miles per hour consistently but nothing else in the house is running (no AC's, etc).

I use a Camco 10 foot extension cord which I removed to test charging with just the cable that came out the car and it's the same rate.

Any ideas on what could be causing the sudden slow down?

I should add the voltage of 207V hasn't changed.

 

[P85_DA]

You have wrong size breaker for 14-50 ..should be a 50a..not sure rest of setup including wire size to outlet..also what amps is car set too in mcu ?

 

[eprosenx]

Hi I have a Nema 1450 outlet attached to my panel on a 40 watt breaker that usually puts out a decent charge for my model X. I typically get 15 miles per hour but recently it dropped to 7 miles per hour consistently but nothing else in the house is running (no AC's, etc).

I use a Camco 10 foot extension cord which I removed to test charging with just the cable that came out the car and it's the same rate.

Any ideas on what could be causing the sudden slow down?

As @P85_DA points out, you likely mean 40amp breaker, not 40 watt. If such a thing existed it would be hilariously slow (would not even be able to run the cooling pumps and such).

Do you have a UMC gen 1 or a UMC gen 2? If a gen 1 then that is a bad idea on a 40a circuit.

There is nothing against the rules about a 40a breaker on a 14-50 receptacle as long as your intended load does not need more than 40a (32a continuous). Though generally we always recommend installing wire and a breaker capable of the full 50a. A UMC gen 2 maxes at 32a so it matches with a 40a breaker nicely.

Are you in a condo building or other commercial style building? 207v is massively low (and concerning) if you have a standard 240v electrical feed, but if you are off a 3 phase 208v system then you are spot on. If you are on a 240v system then there is some major issue that could be dangerous.

Is the car giving any error messages aboit a hot outlet or a reduced charging rate? If something is wrong with the wiring then the car might be backing off the charge rate due to the voltage drop. Or if the UMC is not locking into the connector properly it will severely limit allowed charge current.

But also, the simplest thing, do verify that the charge rate is set to the maximum number of amps it will allow you to set it to. Perhaps it got bumped.

Please report back what you find!

 

[Derek Kessler]

Half the charge rate? Sounds like one of the two hot lines has disconnected somewhere along the line. Either at the breaker, in the receptacle, or the UMC itself.

 

[mxnym]

Half the charge rate? Sounds like one of the two hot lines has disconnected somewhere along the line. Either at the breaker, in the receptacle, or the UMC itself.

If one of the hot lines was disconnected, wouldn't the voltage reading also cut in half? That having been said, this reminds me that I saw something somewhere (possibly in this forum, possibly on reddit) about 3-phase systems not always playing nicely with the UMC. It's a vague memory at this point, but it seems like it had something to do with the UMC requiring a specific configuration while code allowed for a different one. In such a case, the 3-phase compatibility issue might make more sense than a disconnected hot line.

 

[eprosenx]

Half the charge rate? Sounds like one of the two hot lines has disconnected somewhere along the line. Either at the breaker, in the receptacle, or the UMC itself.

If a hot become disconnected then there would b zero potential between the terminals so you would get a reading if zero volts.

The only way to get a reading of half 240 would be if you replaces one “hot” with neutral, or <shudder> ground (but carrying current over ground would be a horribly dangerous idea).

 

[Jimmy T]

As @P85_DA points out, you likely mean 40amp breaker, not 40 watt. If such a thing existed it would be hilariously slow (would not even be able to run the cooling pumps and such).

Do you have a UMC gen 1 or a UMC gen 2? If a gen 1 then that is a bad idea on a 40a circuit.

There is nothing against the rules about a 40a breaker on a 14-50 receptacle as long as your intended load does not need more than 40a (32a continuous). Though generally we always recommend installing wire and a breaker capable of the full 50a. A UMC gen 2 maxes at 32a so it matches with a 40a breaker nicely.

Are you in a condo building or other commercial style building? 207v is massively low (and concerning) if you have a standard 240v electrical feed, but if you are off a 3 phase 208v system then you are spot on. If you are on a 240v system then there is some major issue that could be dangerous.

Is the car giving any error messages aboit a hot outlet or a reduced charging rate? If something is wrong with the wiring then the car might be backing off the charge rate due to the voltage drop. Or if the UMC is not locking into the connector properly it will severely limit allowed charge current.

But also, the simplest thing, do verify that the charge rate is set to the maximum number of amps it will allow you to set it to. Perhaps it got bumped.

Please report back what you find!

Yes, 40 Amp! I have the UMC Gen 2 charger which caps at 32a. I'm in a private house so I have the access to the panel. I installed the nema 1450 outlet outside myself with a buddy who is electrically inclined :-D (famous last words). I believe it's a 3 phase system if that means a black, red and white wire and ground. The connections made to an existing line are secure and not in a place where there is a lot of movement. No message about reduced charging at all. The max # of amps is at 32. It only goes higher when I supercharge. I think I answered everything, but let me know if I missed something. And thanks for the reply!

 

[Jimmy T]

Half the charge rate? Sounds like one of the two hot lines has disconnected somewhere along the line. Either at the breaker, in the receptacle, or the UMC itself.

That's what I was thinking because it doesn't seem like coincidence that it's exactly half the original rate, but weirder things have happened... could be a coincidence detracting from the root of the problem.

 

[Jimmy T]

If a hot become disconnected then there would b zero potential between the terminals so you would get a reading if zero volts.

The only way to get a reading of half 240 would be if you replaces one “hot” with neutral, or <shudder> ground (but carrying current over ground would be a horribly dangerous idea).

Definitely didn't use ground for anything like that!

 

[Jimmy T]

You have wrong size breaker for 14-50 ..should be a 50a..not sure rest of setup including wire size to outlet..also what amps is car set too in mcu ?

As others noted, I have the UMC 2 so it's capped at 32 amp so the 40 amp breaker should be okay. Still, a good thought, thank you! See my responses below if you have a second and let me know what you think.

 

[eprosenx]

Yes, 40 Amp! I have the UMC Gen 2 charger which caps at 32a. I'm in a private house so I have the access to the panel. I installed the nema 1450 outlet outside myself with a buddy who is electrically inclined :-D (famous last words). I believe it's a 3 phase system if that means a black, red and white wire and ground. The connections made to an existing line are secure and not in a place where there is a lot of movement. No message about reduced charging at all. The max # of amps is at 32. It only goes higher when I supercharge. I think I answered everything, but let me know if I missed something. And thanks for the reply!

What type of wire did you use for the installation? What Wire gauge? Copper or Aluminum? Is it NM style cable (Romex), or other? Is it in conduit or exposed?

Red, Black. White, and ground is typically indicative of a single phase system but with "split phase" (180 degrees out of phase with each other). So nominally is 120v from neutral to either hot, or 240v from hot to hot. 207v is very bad in this kind of system. That is a ton of voltage drop. Do either you or your buddy have access to a multimeter? You should take voltage readings at your panel and the receptacle while it is not under load (those are likely to be the same when not under load). Then maybe again at the panel but while your car is charging.

If you can't do this with a multimeter, perhaps one quick test would be to plug the car in and immediately watch the voltage on the car display as it first starts charging and then continue watching it as it ramps current to see how much it drops.

Pictures of your install and panel and such could also be helpful FWIW. 207v concerns me. You may have a dangerous situation going.

 

[Jimmy T]

What type of wire did you use for the installation? What Wire gauge? Copper or Aluminum? Is it NM style cable (Romex), or other? Is it in conduit or exposed?

Red, Black. White, and ground is typically indicative of a single phase system but with "split phase" (180 degrees out of phase with each other). So nominally is 120v from neutral to either hot, or 240v from hot to hot. 207v is very bad in this kind of system. That is a ton of voltage drop. Do either you or your buddy have access to a multimeter? You should take voltage readings at your panel and the receptacle while it is not under load (those are likely to be the same when not under load). Then maybe again at the panel but while your car is charging.

If you can't do this with a multimeter, perhaps one quick test would be to plug the car in and immediately watch the voltage on the car display as it first starts charging and then continue watching it as it ramps current to see how much it drops.

Pictures of your install and panel and such could also be helpful FWIW. 207v concerns me. You may have a dangerous situation going.

okay thanks for the quick reply. I can look at everything you mentioned. I dont have a multimeter, but my buddy does. Will try to get him over. I can do the test you suggested to watch from the car screen.

It's copper wire, 6 gauge (HUGE) and it's black,red,white,ground in a black soft sheathing. Exposed but the wire goes to the outlet and isn't exposed to the outside at all. Caulked around outlet and the hole before the outlet was placed.

 

[Jimmy T]

Also, another theory from a friend who is electrically inclined, he mentioned that since it's a half, perhaps the breaker (one half) went bad and that's the cause. Any thoughts on that?

 

[Derek Kessler]

Also, another theory from a friend who is electrically inclined, he mentioned that since it's a half, perhaps the breaker (one half) went bad and that's the cause. Any thoughts on that?

It's possible. You can pick up a basic non-contact voltage tester from Lowes or Home Depot for less than $20 to help trace where the problem is occurring.

 

[eprosenx]

Also, another theory from a friend who is electrically inclined, he mentioned that since it's a half, perhaps the breaker (one half) went bad and that's the cause. Any thoughts on that?

Doubtful. If one half of the breaker failed you would again get zero voltage potential (assuming one side opened and the other did not).

Also, I don’t think a non contact voltage tester would be useful in this case. They are really just for detecting if a wire might be hot for safely reasons. They won’t tell you anything useful about voltage and AC will radiate from one wire to another in a parallel set of wires.

 

[Jimmy T]

Guys, I think I might be an idiot and maybe nothing is wrong. I think I can tie the change to the recent Android Tesla app update in terms of timeframe. In the new version of the Android app the charging is stated in Kw's while the previous version showed it as Mph/Hr.

See the attached screenshots of the before and after (screen shot with blue circles is the old, no circles is recent)

I think I'm getting the same charge and got confused by the change in display units!