Wall charger not charging at 48A

Wall charger not charging at 48A


I have a Tesla wall charger connected directly to a 60A breaker on my sub panel. When I first installed it I confirmed it was charging at 48A. I normally set the charge time at 1AM so I haven't been monitoring the charge rate. I just checked this morning and it is only charging at 32A. Anyone know if any of the recent firmwares reduced limiting the charge rate? I have a LR RWD.


Magic 8 Ball | 18/05/2019

Did you check when it was near end of charge?

tri_t_to | 18/05/2019

No it is just starting. Actually I unplugged and replugged the charger couple of times and it is charging back at 48A.

Magic 8 Ball | 18/05/2019

Glitch in the matrix ??? NIce you are back to normal.

tri_t_to | 18/05/2019

Spoke too soon. Charging dropped back to 32A after about 5 mins. I am only at 60% charge.

kevin_rf | 18/05/2019

What's your voltage? Close to 240v it down to about 210v? That would indicate a wiring problem and the car is protecting itself.

tri_t_to | 18/05/2019

It's hovering around 231V.

kevin_rf | 18/05/2019

While a little low, that shouldn't be it. Mines usually in the the 234/235v range. The car does measure the voltage before it starts charging, and if it drops while charging it can lower the current.

Have you tried charging frpom a low charge state, less than ~80 miles range left. That's the point the battery will be soaking up every election it can.

Tronguy | 18/05/2019

@tri_t_to: So, nominal voltage at a house is 120 VAC on one phase, 120 VAC on the other phase, and, across the two phases, 240 VAC. At my place, it's around 243 or 245, depending upon the phase of moon, how many other people in the development have their air conditioners on, and so forth.
Next: Wires have got resistance. Voltage drop (Ohms Law) is V = I * R, where I is current.
Now, when the electrician wired it all up, he used a great big gauge of wire with really low resistance, the better not to burn up stuff. (Power dissipated in the wire is P = I*I*R; too much resistance and stuff starts smoking...)
Further, given that the Wall Connector runs on two phases and ground, in the schemes of What Could Possibly Go Wrong means that one wire might not be crimped/screwed/socketed down as well as the other.. which again leads to higher resistance and a drop in voltage as the current goes up.
In the interests of Safety, the Tesla will drop the charging current if it thinks that there's too much voltage drop from the open circuit (no current draw) to the max current draw case. For example: When I plug the mobile connector into the wall socket next to the breaker panel, it draws 12A. Put in a 30' extension cord, non-heavy duty, and the Telsa drops the charging current to 8A or less.
So, what's going on? Let me count the ways...
1. When the electrician put in the wires, he didn't screw something down like he shoulda.
2. When the electrician put in the wires, he used too small a gauge.
3. There's something buggered up in the switches in the Wall Connector. (I have seen buggered up fresh switches in my career, it happens.)
4. There's something wrong about your connection to the Civil Power Authorities on the breaker panel. (Watch those home improvement shows.. They sometimes get overly warm breaker panels, for all the wrong reasons.)
5. Something wrong about the detection of the voltage drop in the guts of the car charger. Lots of cars get built, one sometimes gets infant mortality.

OK. I'm a EE. My knee-jerk reaction to this would probably be to call the electrician who did the work and politely complain. Further: If you used a Tesla-certified electrician, the ones I used took pretty pictures of their handiwork and sent them into Tesla, I presume so that Tesla could do a little troubleshooting. So, you might call Tesla, if you used a Tesla-certified guy.

Now, I might do this, but I've worked around high-voltage stuff that makes house wiring look silly. Turn off the breaker, take off the TWC cover, tack a couple of 30 GA wires onto the business end of the cable inside the TWC, bring those out to a voltmeter, put the cover back on, carefully, being careful not to short anything, and turn the power on. Check the open-circuit voltage; plug in the car; read the voltage, check the current draw in the screen, and work up to R = delta-V/I. Then see if R makes sense with respect to the wall wire used. But - if you're not handy with stuff like that, Don't Do It.

surfpearl | 18/05/2019

Are you seeing a yellow flashing light on the Tesla Wall Connector? The troubleshooting section of its manual (page 22) mentions 3 cases where the charging current is reduced because of high temperature detected in:
1. The Vehicle Connector (1 yellow flash)
2. The wall plug or on the input terminals to the Wall Connector (2 yellow flashes)
3. The Wall Connector (3 yellow flashes)

Are you seeing a blinking amber light on the car's charge port light? According to the car manual, that indicates Model 3 is charging at a reduced current. The car can limit the charging current and will sometimes display a message explaining the reason for it.

You can also lower the max. charge current on the flatscreen from 48 A to 40 A when starting a new charging session to see if further reduction will be done by the smarts in the car or the Wall Connector.

tri_t_to | 18/05/2019

I drove the car down to 17% and still charging at 32A. There isn’t much load on the sub panel right now. Just a few recess lighting and the frig. The electrical work was done with permits and the inspector was very anal so I don’t doubt the electrician’s work.

Magic 8 Ball | 18/05/2019

If you have a friend with a TESLA have them try your charger.

hammer @OR-US | 18/05/2019

Sorry if this is a stupid question but have you checked the manual charge current setting in the car? Sometimes one of my wall chargers will exhibit a momentary drop in voltage because it's on the same subpanel as a heat pump which pulls a lot of momentary current. When this happens the current drops to 30 (from 40) and the car remembers this and will only charge at 30 until I manually change it back to 40.

jexlean | 18/05/2019

I believe it is the PCS or Power Conversion System. I am having a similar problem with my car. I thought it was my Tesla Wall Connector, but brought the car to the Tesla SC and plugged it into their Wall Connector and sure enough I was only drawing the same max 32A which the display showed source at 48A. The one major difference in my case is that I had a display warning that I am not charging at the maximum rate and to unplug and plug again. Unplugging and plugging again didn't help. PCS is on back order and waiting for repair.

Tronguy | 19/05/2019

Just a bit more under the What Could Possibly Go Wrong categories:
@jexlean: Cool. Plug the car into a known good system and Magic Badly Occurs, and associated with a buggered-up car internal.
@hammer: Spiffy. You get a voltage drop when the heat pump goes off and the logic of the car internals makes the car think that _it_ had caused that. Rube Goldberg, move over.
@Magic 8 Ball: Good idea. If one can't swap the charging establishment by taking the car to a SC with a known good WC, then check the home environment by swapping with a Known Good Car (KGC). Just have to make sure that the KGC is the type that can actually charge at 40A or more.
Finally: I said something previous about possible bad switches in the TWC. Actually, should have thrown possible calumnies at everything about the TWC. Could be bad electronics, switches, wiring, you name it. M8B's got the right idea. Now you need to find a friendly owner nearby :).

Magic 8 Ball | 19/05/2019

Isolating variable is fundamental to understanding at this level.

007bond | 19/05/2019

@hammer @OR-US this is what I thought too it happens to me once in a great while for no reason I find the car set to 32amps max and I just put it back to 48amps and problem solved. This has happen to me maybe 2-3 times in the past several months. I think it may have to do with when I use a public charger since many of them are limited to 32amps but not 100% sure.

tri_t_to | 19/05/2019

Screen says 32/48A. I was able to temporarily get it to charge at 48A yesterday but replugging it a few times but I cannot get it to go to 48A at all since then. Thanks jexlean, I'll have Tesla SC see if it is the PCS.

surfpearl | 19/05/2019

So what color is the Tesla logo on the charge port light when you get 32 A?