Drop in amps after a couple hours.

[daybreakca]

Hi, new to the EV world. I have a Y. I have an outlet 5-20 that I am using for charging. I bought the mobile connector with the 5-20 adapter. what I am seeing is that it will start charging at 6 mph at 16/16. About an hour or two later, it will drop to 4mph at 12/16. I set the car to charge to 80%. Is this normal? Not sure if there is anything to do to keep the car charging at 6mph.

at this time, I have no option to install a level 2 outlet as I live in a condo and the outlet I used in located inside my storage that is directly in front of my parking space. If I can maintain the charge rate of 6 mph, it would be sufficient for my driving habit.

please let me know if you have an suggestions. Also, i live in Los Angeles so cold weather is not an issue.

 

[mongo]

Hi, new to the EV world. I have a Y. I have an outlet 5-20 that I am using for charging. I bought the mobile connector with the 5-20 adapter. what I am seeing is that it will start charging at 6 mph at 16/16. About an hour or two later, it will drop to 4mph at 12/16. I set the car to charge to 80%. Is this normal? Not sure if there is anything to do to keep the car charging at 6mph.

at this time, I have no option to install a level 2 outlet as I live in a condo and the outlet I used in located inside my storage that is directly in front of my parking space. If I can maintain the charge rate of 6 mph, it would be sufficient for my driving habit.

please let me know if you have an suggestions. Also, i live in Los Angeles so cold weather is not an issue.

What voltage does the car display when charging vs not? Could be supply wiring resistance.

 

[Cosmacelf]

The car is detecting some sort of heat build up in the circuit somewhere. I would take apart that 5-20 outlet and make sure the wires are properly screwed tightly, and for sure not backstabbed.

 

[mongo]

The car is detecting some sort of heat build up in the circuit somewhere. I would take apart that 5-20 outlet and make sure the wires are properly screwed tightly, and for sure not backstabbed.

Do you mean the mobile connector is detecting heat build up? If so, the /16 should drop, not the numerator.
The car might be reacting to the charge port temp, which would be a port/ connector issue (but unlikely at only 16 amps).

 

[Rocky_H]

I don't think it's detecting it by temperature, but by voltage drop. People saw this frequently years ago when the old mobile connector could draw 40A from a 14-50 outlet. The car will measure the voltage unloaded, and then compare it again to when it ramps up the current draw. If the voltage drops a lot, then it will recognize that as a probable weak connection in the circuit, and it will drop the current draw to 3/4 of what it was. So people's cars would switch to 30/40 amps. With yours dropping to 12/16, that is also the 3/4 lowering, so I think it's that voltage drop issue. Same things to look at though, like pulling the outlet to make sure wires are tight.

 

[mongo]

I don't think it's detecting it by temperature, but by voltage drop. People saw this frequently years ago when the old mobile connector could draw 40A from a 14-50 outlet. The car will measure the voltage unloaded, and then compare it again to when it ramps up the current draw. If the voltage drops a lot, then it will recognize that as a probable weak connection in the circuit, and it will drop the current draw to 3/4 of what it was. So people's cars would switch to 30/40 amps. With yours dropping to 12/16, that is also the 3/4 lowering, so I think it's that voltage drop issue. Same things to look at though, like pulling the outlet to make sure wires are tight.

Could also be the neighborhood on a shared transformer that sags during the day.
Or, more interesting, a poor neutral connection at the electrical service.

 

[daybreakca]

What voltage does the car display when charging vs not? Could be supply wiring resistance.

So when I stop the charge and restart the charging about 20 seconds later, it goes back up to 6mph for maybe an hour or so before it drops again. at 6mph the voltage is somewhere around 109 to 112

i literally just got my mobile connector less then a week ago so home charging and what to expect is all new to me.

Could also be the neighborhood on a shared transformer that sags during the day.
Or, more interesting, a poor neutral connection at the electrical service.

 

[mongo]

So when I stop the charge and restart the charging about 20 seconds later, it goes back up to 6mph for maybe an hour or so before it drops again. at 6mph the voltage is somewhere around 109 to 112

i literally just got my mobile connector less then a week ago so home charging and what to expect is all new to me.

109 is almost 10% off nominal. Restarting the charge session clears the fault/ reduced charge rate. Could point to something else intermittently pulling down the voltage (like a bunch of condo air conditioners kicking on).

To check if it's wiring, collect a couple voltage points at low/no charging and at 16 Amps (at back to back times)

 

[daybreakca]

As you can see the voltage is between 109 to 111 even when the amp drops.
i got an electrician to switch my outlet from 5-15 to 5-20 just before I started using the mobile connector so I am not sure if there are any loose wiring.

 

[dinonugget]

My NEMA 14-50 outlet w/ Mobile Connector would start at 32A, then slowly drop until 16A. I looked at the car screen and saw a warning about the connector overheating.

After changing out my Leviton 14-50 outlet for a Bryant 14-50, my charging amps is now rock solid at 32A, day after day. In the case of the OP, I agree with the other posts that flaky wiring in the outlet could be a probable cause.

 

[mongo]

As you can see the voltage is between 109 to 111 even when the amp drops.
i got an electrician to switch my outlet from 5-15 to 5-20 just before I started using the mobile connector so I am not sure if there are any loose wiring.

That shows 2V and 4A which would be 0.5 ohm and an 8V drop @ 16Amps. That isn't good, but its also low resolution. Really need a 4 or 0 amp reading to see what the baseline is.
Did they just swap outlets and breaker, or did they check wire gauge and such?

 

[daybreakca]

That shows 2V and 4A which would be 0.5 ohm and an 8V drop @ 16Amps. That isn't good, but its also low resolution. Really need a 4 or 0 amp reading to see what the baseline is.
Did they just swap outlets and breaker, or did they check wire gauge and such?

I believe they just swap out the outlet.

 

[mongo]

I believe they just swap out the outlet.

Since it is a garage, it may have been a 20Amp circuit to begin with.

 

[dafish]

First, read this: Voltage Ratings: 110/115/120, 220/230/240 or 440/460/480

so minimum of 116v at the pole/transformer, whatever feeding your condo. Are you seeing more voltage drop than you should? Well yes, but it’s certainly possible.

then you have these situations:

Con Edison Reduces Voltage System-Wide | Consolidated Edison, Inc.

To help keep electric power flowing reliably during a record-breaking heat wave, Con Edison reduced electric voltage today by five percent system-wide. In addition, it urged its 3 million customers to work with the company by curtailing unnecessary use of energy-intensive equipment, including

conedison.gcs-web.com

CVR Is Here to Stay

Conservation voltage reduction enables utilities to achieve significant energy and peak demand reduction at little cost and without customer impact.

www.tdworld.com

As to why you’re seeing fall-off over time, I got nothing to add.

 

[daybreakca]

Since it is a garage, it may have been a 20Amp circuit to begin with.

The electrician did say it was a 20amp circuit. it is in a garage. So i am guessing that I need to get the electrician out again to check out the issue.

 

[dafish]

maybe charge elsewhere to confirm the behavior is unique to your circuit?

 

[daybreakca]

maybe charge elsewhere to confirm the behavior is unique to your circuit?

This is a great idea. Thanks.

 

[ucmndd]

As you can see the voltage is between 109 to 111 even when the amp drops.

That’s low for a 120v circuit.

What does the car show for voltage right when you start charging, at the very beginning of a session?

 

[davewill]

It's seriously time to check all the wiring for that circuit. Not only the outlet in question, but any outlets that the circuit may be daisy-chained through. Turn off the breaker and use an outlet tester to identify all of the outlets on the circuit. Verify that none of the connections show signs of overheating. Check that none of the connections is back-stabbed, especially not daisy-chained through an outlet by back-stabbing. Finally, check the connections at the panel are tight and correct.

Also make sure nothing else is being run off that circuit, like your hair dryer or garage door opener.

It may turn out to be something else pulling the voltage down, but this is the first step.

 

[dafish]

OP:

Let me own up to a few mistakes I made typing too quickly. The industry acceptable standard for 120v low voltage is 114V, not 116, and it would be measured at your meter, not their transformer. Stupid mistakes on my part, sorry. Moving on, realize the equipment side, largely attributed to internal wiring voltage loss, is an additional 5% (of 120v). That means that a voltage of 108v at a receptacle may or may not be within the utilities policy, but it would be within accepted industry standards.

I'd still call the utility to have the meter checked, but in todays world lower voltage, as per posts I shared, is becoming accepted practice.

Dave's advice above is well spoken, and you'll note a consensus among those of us relatively comfortable with AC.

BTW, and I cannot speak to the "why's", I've noticed that the OBC most certainly has some variance parameters whereby it will limit its power consumption. I cannot tell you if that's sine wave jitter, voltage sag, OBC internal temperature, or other, but I've certainly seen it happen a few times. BTW, I'm sure you know some loads will run hotter on lower voltages. Will an OBC? I would think not, for I believe they strictly limit amperage, but I don't know this for fact.