Wall Connector Charging Slowed from 40 amps to 30 amps?

[Vince Cobelo]

I had my wall connector installed with on a 240v 80/100 and set the dip switches for 40 amp output. Originally when it was put in it was pumping out the 40 amps and I was getting about 30 mph. But now it is only putting out 30 amps and I'm getting about 22 mph.

Has this happened to anyone else? Any ideas why this has happened and what the fix might be?

 

[mjcostajr]

I noticed the same thing the other day, turned out the max amps in car was changed from 40 amp to 30 amp (maybe someone hit it by accident). Did you check your charge settings? (Sorry if this seems too simple but it's what happened with me).

 

[Vince Cobelo]

I noticed the same thing the other day, turned out the max amps in car was changed from 40 amp to 30 amp (maybe someone hit it by accident). Did you check your charge settings? (Sorry if this seems too simple but it's what happened with me).

Nope but I'll check it. Maybe something with the 7.1 upgrade? Thanks.

 

[PatD]

I have this happen occasionally with mine. My S occasionally sets itself down to 30 amps. I think the few times I've seen this has been when our power went out or there was a power issue. Haven't had it happen in months now.

 

[msnow]

Try setting it to 38 amps and start charging. If it takes the 38 amps stop charging and go back to timed charging mode. It will remember the location and amperage of your last successful charge.

 

[Brass Guy]

This is a documented software feature that was added some time ago. IIRC, a sub-version of V5. If the car detects certain power fluctuations, it will automatically set the current to 75% of the max the connector allows.
I'm using the UMC with NEMA 14-50. If I allow the car to charge at 40A, it reduces to 30A occasionally. Not every night, but often. I've been charging at 34A for a while with no reduction, and it's fast enough anyway.

As I've noted before, the problem with this software feature is that if you've reduced the power (to 24A say) like I did when I used a homemade adapter for a 30A plug, when the car detected a power issue it set it to 75% of the max; so it actually bumped it up to 30A.

 

[tel]

This has been my experience since day 1. I have a NEMA 14-50 installed, and I've set it to deliver 40A. It starts delivering the charge at that amperage, but the car ALWAYS dials itself down to 30A. I've stopped stressing about this, as I assume the car knows what it's doing with the power. It also doesn't make too much difference to me, as I can still do almost any amount of charging I need at 30A overnight.

 

[mspohr]

I had my wall connector installed with on a 240v 80/100 and set the dip switches for 40 amp output. Originally when it was put in it was pumping out the 40 amps and I was getting about 30 mph. But now it is only putting out 30 amps and I'm getting about 22 mph.

Has this happened to anyone else? Any ideas why this has happened and what the fix might be?

What's your voltage? If the voltage drops,the car will dial back the current.

 

[ddimit]

This has been my experience since day 1. I have a NEMA 14-50 installed, and I've set it to deliver 40A. It starts delivering the charge at that amperage, but the car ALWAYS dials itself down to 30A. I've stopped stressing about this, as I assume the car knows what it's doing with the power. It also doesn't make too much difference to me, as I can still do almost any amount of charging I need at 30A overnight.

.
.
If your car is dropping the current you have something going on with your wiring or Utility transformer causing your voltage to sag. Can be something as serious as loose connection in your wiring at home. Or the transformer feeding the house is failing or undersized.

Definitely worth checking out

 

[supratachophobia]

I've basically given up troubleshooting this. I've had this problem since day 1. They've done multiple chargers, umcs, charge ports. I've had two electricians who swear they've never seen a better 240v signal. Nothing in the house is overloading the breaker box, especially not in the winter, yet it gets more and more frequent.

 

[FlasherZ]

Take a look at my FAQ - in my signature, or in the North America charging area.

Your car is detecting a failure of the electrical infrastructure connecting your car. There is a question dedicated to addressing that in the FAQ.

 

[Vince Cobelo]

Thank you for all of the comments. I checked the software in the car and confirmed it is set at 40 amps. The feed is definitely 240v. This system was set up so that if I chose to add the second charger all I would have to do is swap out the breakers. All of the wiring, conduit and whatever is to code for 80/100.

My next action will be to vary the amperage in the car and see is something will kick it up to where it once was. I really really doubt it could be the service level. If nothing else works I'll have the electrician back out but this guy is a master electrician. Yea...even experts can make mistakes but I'll eliminate everything else first.

One comment was that the lower amperage is enough and frankly I agree. I really don't need to charge at the higher rate but because it all worked right at one point puzzles me and I don't like unsolved puzzles.

Update: Ok...this is bizzare. Just after writing the above I went out to the car while charging and it was at the charge screen and indicating 30 amps. I upped it to 40 and it immediately went to that level. BTW...its showing a tad above 240v. Varying slightly. Tracking this now via Visible Tesla. hmmm....

 

[linkster]

VC

Most likely power company/voltage sag/voltage wiggle as others have suggested. However, i would turn off the main load center breaker and check the torque on your wire connections at the breaker and inside the HPWC and visually inspect said connections for any possible discoloration/over heating issues.

 

[mspohr]

May be transient noise or sagging voltage. Best way to track it is to have the power company put a monitor on the line for a few days. It should record the voltage. Even short drops in voltage will cause the car to dial back the current.
My neighborhood has eight houses on a single 25 kw transformer. The voltage drops to 230 regularly.

 

[GHammer]

Same thing happens to me occasionally (once a month) and I have concluded it is the utility voltage sagging. I live in a rural area and am the last house on the utility line and when I charge at night the voltage runs about 236. During the day, when my solar is supplying the power it is a rock steady 240.

 

[FlasherZ]

Update: Ok...this is bizzare. Just after writing the above I went out to the car while charging and it was at the charge screen and indicating 30 amps. I upped it to 40 and it immediately went to that level. BTW...its showing a tad above 240v. Varying slightly. Tracking this now via Visible Tesla. hmmm....

Hi Vince, I've seen this before. It's a side effect of the car remembering the charge current. You can easily reproduce this:

1. Start charging at 40A; car backs off to 30A due to some kind of transient condition.
2. Play with the charging current in the car - back it down to 29, then increase back to 30. While you're not permitted to increase beyond 30A because the car had backed off, the car now remembers charging current of 30A for that location.
3. Go do your normal thing... drive away, come back the next day...
4. Come back to that spot and plug in, location-based charging current awareness starts charging the car at 30A, despite the availability of 40A.

To defeat this, while the car is unplugged, go to the charging screen (the lightning bolt icon on the touchscreen) and set it all the way up to the max again, then plug in. It should have reset.

- - - Updated - - -

Same thing happens to me occasionally (once a month) and I have concluded it is the utility voltage sagging. I live in a rural area and am the last house on the utility line and when I charge at night the voltage runs about 236. During the day, when my solar is supplying the power it is a rock steady 240.

There are many reasons it could be happening - see my FAQ (in my signature below, or in this thread: FAQ: Home Tesla charging infrastructure QA ) for more information:

• The UMC/HPWC/J1772 connector contacts to the car could be dirty or loose, causing a higher resistance in the connection, which will generate significant amounts of heat. Check to see if the connector to the car is hot to the touch (warm is ok, hot is not).
• The UMC or its adapter contacts at the NEMA 14-50 receptacle could be dirty or loose, causing a high resistance connection. Check to see if the UMC plug is hot to the touch (warm is ok, hot is not).
• Wiring at the branch circuit receptacle or breaker may be loose. Be alert for hot electrical smells or melting plastic smells as your car is charging.
• The branch circuit conductors / wires may be undersized if there is a very long run (> 100 ft.) from the location's electrical panel, causing a larger-than-normal voltage drop. Voltage drop as seen by the car between 0A charging and the maximum charge current should be less than 5%.
• Another high-current appliance in the home may be experiencing a problem. For example, a bad start capacitor in an air conditioning compressor or furnace blower may result in a very high load during start-up for a longer-than-usual period of time. The Tesla may respond to this by backing off.
• Service conductors feeding the location from the power company may be undersized or damaged. These cables do not have to follow the same rules as wiring for the inside of the home, and sometimes are undersized. As an example, prior to my upgrades for the Tesla, my home had a 200A rated service being delivered over 2/0 AWG ("two-aught") aluminum cable; the NEC's tables determine that cable is sufficient only for 135A. Undersized cables, or those even slightly damaged by digging or other causes, will create a voltage drop at high loads that may trigger the Tesla to back away.
• Utility transformers feeding the home may be undersized or failing. These transformers are sometimes very old (in some cases, transformers have been in place for 50 years) and typically serve two or more homes. They are typically replaced by the power company when they fail, and in many cases have not kept up with the electrical load growth over time. As an example, prior to my upgrades for the Tesla, my 200A rated service was fed from a 15 kVA-rated transformer, which was rated only at 62A. While these transformers are robust (the power company said they had calculated occasional load spikes of over 200%), they do cause abnormal voltage drops under higher loads.
• The distribution lines from the nearest substation to your transformer may be overloaded due to highly fluctuating loads.

 

[Vince Cobelo]

Its all working fine now. Don't know why.

 

[supratachophobia]

I've had excellent luck with Jerry33's suggestion of setting amperage to 37-38. It's not that much of a sacrifice, and the car won't drop that full 25% if it detects something it doesn't like on the line.

 

[msnow]

I've had excellent luck with Jerry33's suggestion of setting amperage to 37-38. It's not that much of a sacrifice, and the car won't drop that full 25% if it detects something it doesn't like on the line.

This one from above?

Wall Connector Charging Slowed from 40 amps to 30 amps?