10% discrepancy in charge logs

johnmark

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Greetings,

I don't know if this is a real issue, but I found it odd. When I look at my chargepoint logs, I notice it reports 10 percent higher kwh used than the Mach e charge report. Is it common to see that much attenuation between point A and point B? The charging cable is 20 ft long.
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flapjake314

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it spent the 10% heating your house :)

i am not an EE but my understanding is cable length actually does cause inefficiency but that the vast majority of that 10% loss is unavoidable
 
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johnmark

johnmark

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Ah well, looking forward to those cold winter nights then lol
 

portlandg

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You
Greetings,

I don't know if this is a real issue, but I found it odd. When I look at my chargepoint logs, I notice it reports 10 percent higher kwh used than the Mach e charge report. Is it common to see that much attenuation between point A and point B? The charging cable is 20 ft long.
You will find that your chargepoint will always read higher than your MME says. This is because your MME will draw more power to condition your battery/run the electrics during charging/run cooling. It will then charge the battery with whats' left.
 

RickMachE

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You

You will find that your chargepoint will always read higher than your MME says. This is because your MME will draw more power to condition your battery/run the electrics during charging/run cooling. It will then charge the battery with whats' left.
That's not the main reason.

When providing electricity to the vehicle via ANY charger, there is a loss from the wall to the vehicle. Depending on the cable length, wire gauge, etc., that loss could be around 8% or up to 15%. You have loss going from a high speed DC charger also.

Try charging with the 120v adapter. You'll see close to 15% loss.

The other thing to remember is that many charging apps report usage to multiple decimal places. My JuiceBox tells me that yesterday I put in 11.9701kWh. FordPass says I put in 10kWh. That would be a loss of 1-(10/11.9701)=16.46%. However, FordPass doesn't report decimal places. Let's assume I put in 10.44kWh. 1 - (10.44/11.9701) = 12.8% loss. Maybe the FordPass app truncates, instead of rounding. 1 - (10.9/11.9701) = 8.9% loss.

Either way it's a loss. But with the lack of detail in FordPass, it's an inaccurate loss.

Once the current session is ended by unplugging, FordPass will only tell you the percentages. The prior session, my car went from 69% to 90%. Again, that's rounding. Go play with the calculations at 68.46% or 69.44% and 89.46% or 90.44%. I put in as little as 20kWh, or as much as 22kWh. JuiceBox tells me I put in 21.12.
 
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johnmark

johnmark

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Thanks everyone. I feel enlightened now.
 

portlandg

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That's not the main reason.

When providing electricity to the vehicle via ANY charger, there is a loss from the wall to the vehicle. Depending on the cable length, wire gauge, etc., that loss could be around 8% or up to 15%. You have loss going from a high speed DC charger also.

Try charging with the 120v adapter. You'll see close to 15% loss.

The other thing to remember is that many charging apps report usage to multiple decimal places. My JuiceBox tells me that yesterday I put in 11.9701kWh. FordPass says I put in 10kWh. That would be a loss of 1-(10/11.9701)=16.46%. However, FordPass doesn't report decimal places. Let's assume I put in 10.44kWh. 1 - (10.44/11.9701) = 12.8% loss. Maybe the FordPass app truncates, instead of rounding. 1 - (10.9/11.9701) = 8.9% loss.

Either way it's a loss. But with the lack of detail in FordPass, it's an inaccurate loss.

Once the current session is ended by unplugging, FordPass will only tell you the percentages. The prior session, my car went from 69% to 90%. Again, that's rounding. Go play with the calculations at 68.46% or 69.44% and 89.46% or 90.44%. I put in as little as 20kWh, or as much as 22kWh. JuiceBox tells me I put in 21.12.
I was just trying to explain the reason in simple terms that even I could understand.
 

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Exactly what you should see. The Car Charger (built into the Mach E) has to convert AC house power to DC to charge the battery using an inverter. The losses in that module are about 9-10% at 240V and 15% at 110V.
 

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Yeah the missing 10% are charging efficiency losses.
 

RickMachE

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