Confused about charging rate

[Dave T]

I have my PMCC connected to a 50 amp circuit with a NEMA 14-40 plug. I set the PMCC to a 40 amp charge rate. When I plug it into my car, the car says it's charging at .3 miles/minute. I haven't done the math, but that seems low. On the PMCC, it says it's charging at 2.03 kw/h. Shouldn't it be 9.6 kw/Hr? And, I have a power monitoring system in my house that reported an increased draw of about 8000 watts when I started charging the car. So much higher than the car and the PMCC are reporting, but still below the 9600 watts.

Thoughts?

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[MissionC]

I have my PMCC connected to a 50 amp circuit with a NEMA 14-40 plug. I set the PMCC to a 40 amp charge rate. When I plug it into my car, the car says it's charging at .3 miles/minute. I haven't done the math, but that seems low. On the PMCC, it says it's charging at 2.03 kw/h. Shouldn't it be 9.6 kw/Hr? And, I have a power monitoring system in my house that reported an increased draw of about 8000 watts when I started charging the car. So much higher than the car and the PMCC are reporting, but still below the 9600 watts.

Thoughts?

Do you mean a 14-50 outlet? 9.6 kWh is theoretical limit - I generally see around 9 kWh. I did notice that it starts a little slow and then builds up to a higher throughput rate. Does it max out at 2.03 after 20-30 minutes?

 

[Dave T]

Yes, 14-50, sorry.

So the charging rate is going up. It's been about a half hour, and now it says 4.76 kWh on the PMCC. But the issue is that it seems to have been drawing close to 9kw the whole time (according to my power monitoring system), but the PMCC is saying it's less. Could it be pulling more watts than are actually going towards charging the battery?

 

[daveo4EV]

what is your battery % - you won't charge at the full rate as you get close to full on the battery...

.3 miles/min is 18 miles range / hour of charge

screen shot of the PMCC would be helpful with the current rating showing…

 

[Dave T]

what is your battery % - you won't charge at the full rate as you get close to full on the battery...

.3 miles/min is 18 miles range / hour of charge

screen shot of the PMCC would be helpful with the current rating showing…

Ok, see screen shots below. Car says it's charging at .3 mi/min. 70% charge. PMCC says it's drawing .43 kW/h. Power monitor says the house is using 14kw, and it was at about 4kw before the car started charging. So the issue is that the car seems to be drawing the expected amount of power, but says it's using far less than it's drawing. Either the car is misreporting its consumption, or there is a lot of power being thrown out the window. Not sure if that is even possible.

 

[LukeManning]

Ok, see screen shots below. Car says it's charging at .3 mi/min. 70% charge. PMCC says it's drawing .43 kW/h. Power monitor says the house is using 14kw, and it was at about 4kw before the car started charging. So the issue is that the car seems to be drawing the expected amount of power, but says it's using far less than it's drawing. Either the car is misreporting its consumption, or there is a lot of power being thrown out the window. Not sure if that is even possible.

.3 mile per minute is pretty average charging speed at a 70% full battery - that's around 18~ Miles Per Hour of charging.

Most I've seen our Taycan go to on it's wall charger was .5 miles per minute (about 30~ Miles Per Hour) when it was down around 5% State of Charge, and that only lasted a short while.

 

[r553]

Let it charge while you sleep. Wake up to a charged car.

 

[Dave T]

.3 mile per minute is pretty average charging speed at a 70% full battery - that's around 18~ Miles Per Hour of charging.

Most I've seen our Taycan go to on it's wall charger was .5 miles per minute (about 30~ Miles Per Hour) when it was down around 5% State of Charge, and that only lasted a short while.

Yes, thanks, I can also do the math that .3 miles per minute is 18 miles an hour. The issue is that the car seems to be using far less power than is being drawn. So that's wasted electricity and extra $$ on my electric bill. Has anyone else that can monitor their house electricity consumption verified this?

 

[LukeManning]

Yes, thanks, I can also do the math that .3 miles per minute is 18 miles an hour. The issue is that the car seems to be using far less power than is being drawn. So that's wasted electricity and extra $$ on my electric bill. Has anyone else that can monitor their house electricity consumption verified this?

Sorry Dave. Did not intend to make it sound like you didn't know how to do basic math. Just thought you were confused about why it says .3mi/min

I would assume there is some energy loss between your home, the NEMA 14-50 outlet, and the PMCC, and possibly what your home energy consumption is quoting. That being said, how much extra energy loss are you saying you're having from charging the car?

 

[daveo4EV]

@Dave T - I see your confusion

the .43 numbest on the charger is NOT kiloWatts (kW) - it's kilo-watts-HOURS - which is how "MUCH" power your Taycan has consumed during that charging session - the is the gallons of gas metaphor - and that number will grow over time during the charging session as your battery gets full.

you are most likely charging at 39.x/40 amps - which would be approximately 9.6 kilowatts (kW) - Note the lack of the 'h' - and this is confirmed by the .3 mile/min number inside the vehicle. If you tap on the .3 mile/min number on the screen it will change to a "kw" display - and I would expect the number to be about 8.63 kW inside the car...

there is about 10% power loss in converting the AC power to DC power - so 9.6 kW from the charger will result in a charge rate of about 8.5 kW at the battery inside the car...

if you tap on the screen on the charger you will can get a display that will show you the "amps" as a line at the bottom and it will say something like 39.4 amp of 40 as the power current charge rate...

your car is not charging at .43 kW - it has taken .43 kWh so far in the charging session.

I hope this helps.

 

[daveo4EV]

your display shows .43 kWh for 3 minute of charge

we can do some math and get the charge rate

.43 kWh / 3 min = .143 kWh per minute * 60 minutes (1 hour) = 8.6 kWh - yep that's about right for 40 amp charge session.

 

[daveo4EV]

PMCC says it's drawing .43 kW/h.

it's not drawing .43 kW - it has drawn .43 kW-hours so far - that number is NOT the charge rate - it's the cumulative charge "so far" in the charging session

it took me a while as an EV owner to really understand kW vs. kWh's - but it will get clear...

 

[daveo4EV]

here are the alternate displays that will show the "charge rate" in the car - and the number of amps being "pumped" into he car by the charger…

 

[LukeManning]

it's not drawing .43 kW - it has drawn .43 kW-hours so far - that number is NOT the charge rate - it's the cumulative charge "so far" in the charging session

it took me a while as an EV owner to really understand kW vs. kWh's - but it will get clear...

Thank you for this explanation David. Totally bypassed that when looking at Dave's original photos.

Agree it is very confusing for most people though!

 

[daveo4EV]

I also thinking a sub-optimal German to English translation isn't helping here…

the text is:

0.43 kWh
Power consumption

I'm going to humbly suggest the following text would be more precise

0.43 kWh
Power consumed

it's not consumption at this moment - it's how much power has been consumed so far…

English is a tricky language sometimes.

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