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DC fast charging

2K views 10 replies 6 participants last post by  KiwiME 
#1 ·
I recently used a DC fast charger as I forgot to plug in overnight, so went to a public charger. On the receipt it stated that my car had taken 74.55kWh to charge the battery…it was at 30% when I started charging to 80% of a 64kW battery. Something seems a little off? This was using electrify America, I understand energy loss as heat etc but to have a charger use more than double doesn’t seem right. Does anyone have any insight?
 
#4 ·
Hello Jford.

So you went from 13% to 79%. I.e, you did a 66% charge. 66% of 65kWh (our battery capacity) = 42.9kWh needed for the battery. You “paid” for 44.338kwh; a 1.44kWhr loss (or charging inefficiency). 1.44/42.9 = 3.4% charging efficiency loss. Not bad.

However, the OP has a large phantom load. 😲

-Barry
 
#5 ·
...On the receipt it stated that my car had taken 74.55kWh
…it was at 30% when I started charging to 80% of a 64kW battery.
You haven't mentioned ambient temperature, the average charge rate or if you have a battery heater but I did a test at just under 20°C a while back on my Kona which has the same size and chemistry. I didn't graph SoC as I was more interested in other losses in the EV, however I did note the starting and ending values.
The only unavoidable primary loss should be the battery resistance. At 45.9 kW average I'm seeing 3% loss.

Other potential losses are:
6% if the vender bills on the DC side rather than the AC side. I've never heard of this being the case and it might even be illegal, but it's a possibility.
A significant amount if you have a battery heater. That's apparent in the data that I took as the energy delivered to the battery lagged the energy provided by the charger.

If you look at the cumulative provided and energy delivered you can see the lines become parallel after the heater backs off. That's 100% efficiency to the battery. Other than that it's only that 3% loss that doesn't show up as an SoC increase.

Rectangle Slope Line Font Parallel
 
#6 ·
You haven't mentioned ambient temperature, the average charge rate or if you have a battery heater but I did a test at just under 20°C a while back on my Kona which has the same size and chemistry. I didn't graph SoC as I was more interested in other losses in the EV, however I did note the starting and ending values.
The only unavoidable primary loss should be the battery resistance. At 45.9 kW average I'm seeing 3% loss.

Other potential losses are:
6% if the vender bills on the DC side rather than the AC side. I've never heard of this being the case and it might even be illegal, but it's a possibility.
A significant amount if you have a battery heater. That's apparent in the data that I took as the energy delivered to the battery lagged the energy provided by the charger.

If you look at the cumulative provided and energy delivered you can see the lines become parallel after the heater backs off. That's 100% efficiency to the battery. Other than that it's only that 3% loss that doesn't show up as an SoC increase.

View attachment 8065
Yes effectively for a 32 kW requirement they charged th 74.44kw, I’m in Florida’s temp around 25C, the loss is definitely excessive, considering the cost of gas here at the moment I could drive a car returning 14mpg for the same cost. I know the car has a winter kit but at this point can’t see that as a factor.
 
#9 ·
You're talking about jford53593. His bill is correct except for the 18% tax/fee :( .
 
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