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HPWC only drawing 47A on a 60A (48A cont) breaker

mongo

Well-Known Member
May 3, 2017
16,182
58,593
Michigan
I know the difference is miniscule, but was just wondering why my HPWC on a 60 A breaker was only charging at 47A when it should be charging at 48A.

If the input voltage is over 240 (or so) the car charger hits the power limit (as opposed to the current limit)

Edit: but that is only if you were talking about a 3 that peaks out at 48A. Not sure if the HPWC will power limit also. Other option is voltage drop caused the system to reduce power. What voltage does it read while charging at 47A?
 
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bob_p

Active Member
Apr 5, 2012
3,738
2,949
Our S 100D only has the 48A onboard charger - connected to an HPWC on a 100A circuit, and we often see 47A charging onboard.

The difference between 47 & 48 shouldn't be noticeable. And, as pointed out, this is probably a rounding issue (reporting 47.9 and 47). The simplest fix may be for Tesla to adjust rounding (47.5 and above is reported as 48)...
 
Our S 100D only has the 48A onboard charger - connected to an HPWC on a 100A circuit, and we often see 47A charging onboard.

The difference between 47 & 48 shouldn't be noticeable. And, as pointed out, this is probably a rounding issue (reporting 47.9 and 47). The simplest fix may be for Tesla to adjust rounding (47.5 and above is reported as 48)...

As Mongo said it's the power not the current that is your limit. The "48 Amp" on board charger is capped at 11.5 kW. So if your voltage is 244 or higher, you will see reduced current.
 
As Mongo said it's the power not the current that is your limit. The "48 Amp" on board charger is capped at 11.5 kW. So if your voltage is 244 or higher, you will see reduced current.

Correct... it's all about kW not amps. I noticed this we I charged at a Level 2 charger in a commercial property that had 30A 208V (not 240V) power. SLOW 19mph charge rate (30A x 208V = 6.2kW) vs. FAST 50mph charge rate of our Tesla High Power Wall Charger (80A x 240V = 19.2kW) at our home on our 2018 P85D with dual 40A chargers. Obviously at 6.2kW charging rate it would take ~ 14 hours to fully recharge our 85kWh battery... and 7 hours just to replenish 50%. OUCH

This is why when we take "road trips" out of range of Tesla Superchargers we seek out hotels with Tesla Destination Chargers, not Level 2 chargers. Not only are they significantly faster than L2 chargers, they're rarely blocked by other guest's cars either being charged or ICE'd. Tesla chargers are typically well marked and open... and Tesla owners are typically more courteous, vacating the Tesla charger when they've recharged.

More Level 1 & Level 2 charging info here: https://www.clippercreek.com/wp-con...s-Level-2_Chart_-20180202_final_low-res-1.pdf
 

Rocky_H

Well-Known Member
Feb 19, 2015
8,620
11,203
Boise, ID
This is why when we take "road trips" out of range of Tesla Superchargers we seek out hotels with Tesla Destination Chargers, not Level 2 chargers. Not only are they significantly faster than L2 chargers,
Please don't confuse this. Tesla Destination Chargers are also level 2 chargers.
 
Please don't confuse this. Tesla Destination Chargers are also level 2 chargers.

Technically you're correct. Tesla Wall Chargers are Level 2 chargers since they're limited to 80A x 240V = 19.2kW, or about 70 miles of range per hour of charging.

"However, the charging stations being put in with federal grant money don’t support the full range of Level 2 charging and max out at 6.6kW or around 26 miles of range per hour of charging." Understanding Electric Vehicle Charging - Plug In America This has been our experience with only one exception of a 40A 208V Level 2 charger at a resort in Breckenridge CO. All the other Level 2 chargers we've encountered have been typical SLOW 6.6kW Level 2 chargers outputting 19 to 25 mph charge rates.

So let me restate: This is why when we take "road trips" out of range of Tesla Superchargers we seek out hotels with Tesla Destination Chargers which typically run at 40A x 240V = 9.6kW / 35 miles of range per hour to 80A x 240V = 19.2kW / 70 miles of range per hour, NOT the typical SLOW 6.6kW / 19 to 25 mph Level 2 chargers.

Hopefully the "Department of Corrections" approves meow. :D
 
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No, it's also about amps. A car with a 48a charger in the car won't go over 48a just because the voltage is only 208v. It's a matter of which limit you hit first, amps or watts.

Correct. Your onboard charger will limit your AMPERAGE charge based on what size onboard charger you have. We have dual 40A chargers = 80A so don't run into this limitation... but obviously Teslas with 40A, 48A and 72A chargers won't be able to charge at 80A / 240V = 19.2kW

In summary, SIZE MATTERS:
  • onboard charger amperage
  • charging station kW = Amps x Volts
  • battery SoC ("State of Charge" = the fuller your battery the slower rate it will recharge)
 

Lloyd

Well-Known Member
Supporting Member
Jan 12, 2011
6,410
2,341
San Luis Obispo, CA
I have found that the newer HPWC's when I set them up with Master and Slave will "hunt " a little around the maximum amp rate they are set to. Also if your voltage falls a little you would expect the amperage to NOT be at the maximum. 240 volts is the requirement for meeting the stated amps.
 

mongo

Well-Known Member
May 3, 2017
16,182
58,593
Michigan
I have found that the newer HPWC's when I set them up with Master and Slave will "hunt " a little around the maximum amp rate they are set to. Also if your voltage falls a little you would expect the amperage to NOT be at the maximum. 240 volts is the requirement for meeting the stated amps.

Is it the HPWC hunting, or is it the car charger, since the charge determines the actually draw (with an upper limit from the HPWC communication)? Would need to look at the HPWC to vehicle signal to see where the convergence ssue lies.

Below 240V, the charger will pull max allowable wall amps (but not max power). At least until the input voltage drops too low, at which point charge current/power is reduced to maintain input voltage (to reduce heating in supply wires/ connections).
 

BerTX

Active Member
Supporting Member
May 2, 2014
3,508
3,664
Texas/Washington
Technically you're correct. Tesla Wall Chargers are Level 2 chargers since they're limited to 80A x 240V = 19.2kW, or about 70 miles of range per hour of charging.

"However, the charging stations being put in with federal grant money don’t support the full range of Level 2 charging and max out at 6.6kW or around 26 miles of range per hour of charging." Understanding Electric Vehicle Charging - Plug In America This has been our experience with only one exception of a 40A 208V Level 2 charger at a resort in Breckenridge CO. All the other Level 2 chargers we've encountered have been typical SLOW 6.6kW Level 2 chargers outputting 19 to 25 mph charge rates.

So let me restate: This is why when we take "road trips" out of range of Tesla Superchargers we seek out hotels with Tesla Destination Chargers which typically run at 40A x 240V = 9.6kW / 35 miles of range per hour to 80A x 240V = 19.2kW / 70 miles of range per hour, NOT the typical SLOW 6.6kW / 19 to 25 mph Level 2 chargers.

Hopefully the "Department of Corrections" approves meow. :D
Nope, not approved. The Wall Connectors are L2 chargers no matter what power they put out. The WC can be wired to put out as little as 2.9 kW, and MANY Destination Chargers are lower than the 9.6 kW you seem to expect. Also, some are probably wired to share power between two WCs, so the output could be even lower at times. Simply saying Tesla Destination Chargers are always better is just mistaken.
 

mspohr

Well-Known Member
Jul 27, 2014
11,836
15,672
California
Technically you're correct. Tesla Wall Chargers are Level 2 chargers since they're limited to 80A x 240V = 19.2kW, or about 70 miles of range per hour of charging.

"However, the charging stations being put in with federal grant money don’t support the full range of Level 2 charging and max out at 6.6kW or around 26 miles of range per hour of charging." Understanding Electric Vehicle Charging - Plug In America This has been our experience with only one exception of a 40A 208V Level 2 charger at a resort in Breckenridge CO. All the other Level 2 chargers we've encountered have been typical SLOW 6.6kW Level 2 chargers outputting 19 to 25 mph charge rates.

So let me restate: This is why when we take "road trips" out of range of Tesla Superchargers we seek out hotels with Tesla Destination Chargers which typically run at 40A x 240V = 9.6kW / 35 miles of range per hour to 80A x 240V = 19.2kW / 70 miles of range per hour, NOT the typical SLOW 6.6kW / 19 to 25 mph Level 2 chargers.

Hopefully the "Department of Corrections" approves meow. :D

Most generic Level 2 chargers I have encountered are connected to 208 volts and limit current to 30 amps (about 6 kW) which gives about 20 mph charge rate.
 
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Most generic Level 2 chargers I have encountered are connected to 208 volts and limit current to 30 amps (about 6 kW) which gives about 20 mph charge rate.

EXACTLY my experience:
  • typical Level 2 chargers 6kW = 20 mph
  • typical Tesla Wall Chargers 9.6kW to 19.2kW = 35 to 70 mph
Hence why we seek out hotels with Tesla Destination Chargers vs. typical Level 2 chargers when we're out of Tesla Supercharger range.
 

Lloyd

Well-Known Member
Supporting Member
Jan 12, 2011
6,410
2,341
San Luis Obispo, CA
Is it the HPWC hunting, or is it the car charger, since the charge determines the actually draw (with an upper limit from the HPWC communication)? Would need to look at the HPWC to vehicle signal to see where the convergence ssue lies.

Below 240V, the charger will pull max allowable wall amps (but not max power). At least until the input voltage drops too low, at which point charge current/power is reduced to maintain input voltage (to reduce heating in supply wires/ connections).

Older HPWC's and the HPC on the same circuit do not do this with the same car, thus my comment that it is the newer HPWC's that can be wired in series on the same breaker and load share.
 
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mongo

Well-Known Member
May 3, 2017
16,182
58,593
Michigan
Older HPWC's and the HPC on the same circuit do not do this, thus my comment that it is the newer HPWC's that can be wired in series on the same breaker and load share.
I was just curious, since the master can't know what the car is actually going to draw until it does, I can see the three (HPWC and 2 chargers) taking a while to settle down.
 

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