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What does your max current say when on HPWC?

whitex

Well-Known Member
Sep 30, 2015
6,727
8,563
Seattle area, WA
When I plug in our new Model S into an older HPWC (no side dock) it sometimes says 0/47A and sometimes 0/48A, and then it proceeds to that max number. Sometimes the max changes while charging too. Is this normal, or is it an indication of a problem? What does your say when plugged into an HPWC with sufficient capacity to max out the onboard charger? Does it consistently display the max spec number or does it show lower?
 

navinsiri

Member
Jan 16, 2017
253
430
Central NJ
Mine does the same thing. It automatically adjusts when it detects extra resistance in the wire which can be due to improper connections/wiring, temperature, or a long cable run. Regardless, a change of 1amp is nothing to be concerned about.
 

whitex

Well-Known Member
Sep 30, 2015
6,727
8,563
Seattle area, WA
Mine does the same thing. It automatically adjusts when it detects extra resistance in the wire which can be due to improper connections/wiring, temperature, or a long cable run. Regardless, a change of 1amp is nothing to be concerned about.
Does the actual current go down by 1A (first number) or the max (the second number) go down? I'm a little skeptical that it's caused by resistance because:
  1. This happens as soon as it's plugged in, with 0A current, therefore no way to measure resistance by voltage drop
  2. This particular HPWC is wired solid right next to the electrical service entrance. When charging at 80A voltage stays above 240V no problem
I am also experiencing another issue, where the car throws a charging error every time it completes a charge at 47A or 48A from HPWC. It doesn't do that when completing a charge from 40A mobile connector. The other car charging at 80A from the same HWPC has no problems at all.
 

sundial77

Member
Aug 5, 2018
15
2
49935
I just installed a new gen 2 HPWC with a VERY short run of #4 wire, Since my car only has a 48 amp charger I used a 60 Amp breaker and set the HPWC selector accordingly. It SHOULD be charging at 48 amps but only charges at 47 amps every time. Does anyone know why??
 

tpham07

Active Member
Mar 21, 2017
1,965
2,395
Rhode Island
The second number is the max charge rate. Occasionally that will be lower if the wall connector (stop calling it HPWC people, it hasn't been called that in 3 years) detects the incoming power source to be fluctuating.

This is usually indicative of a high load on your utility power supply. I notice that here in the summer a lot when everyone is running their A/C full blast, and my voltage will sometimes drop to as low as 226V.

I've seen it start at /47A a few times but eventually it goes back up to 48/48A. Probably needs a bit of time to stabilize the incoming power.
 

whitex

Well-Known Member
Sep 30, 2015
6,727
8,563
Seattle area, WA
stop calling it HPWC people, it hasn't been called that in 3 years
Yea, Tesla dropped the "HP" part, but I think people just don't want to call it "WC" (especially in Europe ;)).

I've seen it start at /47A a few times but eventually it goes back up to 48/48A.
I've seen it start up at /47A even when voltage is nice and high, for example 248V. Something got messed up with the newer cars redesign. My old dual charger Tesla always starts at /80A and reaches it no problem. The new one doesn't even reliably work with the Gen1 HPWC (yes, HP applies there).
 

BigNick

Infamous Fat Sweaty Guy
Dec 3, 2017
1,326
1,608
Pennsylvania, USA
You plug your Tesla into a toilet? Isn't that a shock hazard?

I get 40/40A every time, usually 240 to 244V but sometimes as high as 249V.

I have about an 80 foot run of conduit from the 100A breaker in the breaker box to the garage. The breaker is far away enough the contractor installed a disconnect next to the Tesla wall connector. The wire is rated for 100A peak/80A continuous load, but my older Tesla doesn't have the "dual charger" option so it maxes at 40A. I have yet to try it with a car that can charge at 72A or 80A.

I had them run 100A conduit so a faster-charging car or 2nd wall connector could use the extra capacity.
 

Xenoilphobe

Active Member
Jan 2, 2014
4,599
4,515
Fairfax County, Virginia
I get 80 AMPS (2 X 80 so 160 AMPS) with two HPWC's tied into the same power distribution panel. As someone else already stated, the electrical environment has a lot to do with the output at the wall, and yes they are called High Power Wall Connectors - those newer Gen 2 ones have a lower amperage output, so they should call them Lower Power Wall Connector ;)
 

sundial77

Member
Aug 5, 2018
15
2
49935
I just installed a new gen 2 HPWC with a VERY short run of #4 wire, Since my car only has a 48 amp charger I used a 60 Amp breaker and set the HPWC selector accordingly. It SHOULD be charging at 48 amps but only charges at 47 amps every time. Does anyone know why??

The voltage is always around 245 but the max number is always 47 even though I preset it to 48 before connecting the WC cable. It's definitely not a big deal. Guess I'm curious more than anything. My service center said that I can't upgrade to high capacity charging even if I pay the $1900 charge. They said that the option to upgrade was only available to the original owner. Seems odd to me but I don't think I would do it anyway.
 

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