What figure does the % relate to?

[coolshades]

[this might have been answered elsewhere and if so, apologies. i did search, but didn't come up with anything meaningful]

i charge at home for only four hours late in the night when the electrons are the cheapest. my home supply pumps out 29.3 kwh in that much time. this data is from my charger app.

i was casually browsing through Ford Pass's charge logs which reports % rather than kwh.

the app said i had pumped in 31% of charge.

if i do the maths, that's 31% of 94.5 kwh.

shouldn't that be 31% of 88kwh, since that's the usable battery for an AWD ER?

or, shouldn't be 31% of 98 kwh?

i am confused now which figure the % charge on the dash or the app refers to.

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[murphy62]

[this might have been answered elsewhere and if so, apologies. i did search, but didn't come up with anything meaningful]

i charge at home for only four hours late in the night when the electrons are the cheapest. my home supply pumps out 29.3 kwh in that much time. this data is from my charger app.

i was casually browsing through Ford Pass's charge logs which reports % rather than kwh.

the app said i had pumped in 31% of charge.

if i do the maths, that's 31% of 94.5 kwh.

shouldn't that be 31% of 88kwh, since that's the usable battery for an AWD ER?

or, shouldn't be 31% of 98 kwh?

i am confused now which figure the % charge on the dash or the app refers to.

You need to account for the charging losses. Converting AC to DC is inefficient. Multiplying from the resulting DC voltage up to above the battery voltage is inefficient. I've not measured the actual value but try dividing the value reported by the app by 0.7 if using 120 volts AC or by 0.8 if using 240 volts AC.

 

[tannerk89]

You need to account for the charging losses. Converting AC to DC is inefficient. Multiplying from the resulting DC voltage up to above the battery voltage is inefficient. I've not measured the actual value but try dividing the value reported by the app by 0.7 if using 120 volts AC or by 0.8 if using 240 volts AC.

FordPass doesn’t include any sort of charging inefficiencies of the charger when reporting the percentage of battery increase in the charging logs.

@coolshades I’ve been wondering that myself. I believe it should be the % of usable battery, 88kwh, but don’t really know for sure. Usable battery kWh seems to change too much based off environmental conditions for that % increase to be of much value. I would rather see the kWh delivered to the vehicle because I am trying to see how much the charging session cost me, including the charging losses that @murphy62 mentioned.

 

[Murse-In-Airy]

That 31% should be 31% that your battery charge went up. So if you have an 88kwh battery then your battery should have received 27.28 kwh.
Your charger says it sent 29.3kwh to the car, but some of that is lost in heat/ lresistance and physics/chemistry meaning not all energy can preserved in any change in energy state. This shows you lost only about 7% due to charger loss / battery conditioning consumption, which is pretty small.

 

[shutterbug]

i was casually browsing through Ford Pass's charge logs which reports % rather than kwh.

Ford Pass does show kWh received, but only during charging, and not all the time. It will always be less than your charger app.

 

[alexgorod]

All these percentages cannot be taken very seriously.

Yesterday the car was charged to 90%, I had a short round trip of 3.5 + 3.1 miles. So it started at 90%, quickly dropped to 89%, then increased to 92%, and I came home with the battery charged to 89%. FordPass trips report 1.2 + 0.9 kWh, so if I take these numbers seriously, I have a 210 kWh battery! But if the battery really was charged to 92%, and 2.1 kWh = 3%, it's getting me to the promised 2022 increase to 70 kWh!

All I pay attention to is the fact that the displayed percentage is below 40%, so I need to charge. Or if it's Friday

 

[RickMachE]

I believe all trip data includes regenerated electricity...

 

[mkhuffman]

That 31% should be 31% that your battery charge went up. So if you have an 88kwh battery then your battery should have received 27.28 kwh.
Your charger says it sent 29.3kwh to the car, but some of that is lost in heat/ lresistance and physics/chemistry meaning not all energy can preserved in any change in energy state. This shows you lost only about 7% due to charger loss / battery conditioning consumption, which is pretty small.

I believe this is the reason, because typical losses due the charging infrastructure are 5-10%. DCFC can be closer to 10% because of the energy needed to cool the battery when fast charging. Do a Bing search and you can find some articles about it, including links to prior MME forum posts (there are a lot of smart people posting in this forum).

Also, when the car is at 0%, the battery is not totally drained. I don't know the exact figure, but I guess at 0% there is 2-3 kWh of battery remaining. So 100% to 0% is not exactly 88 kWh, it is something closer to 85-86 kWh.

 

[timbop]

The percentage reported by Fordpass is relative to the usable capacity of the battery, but it is an approximation based on precise measurements. As the battery itself changes temperature due to heating/cooling, that measurement can change slightly - which is why the reported percentage can change quickly and/or drift up and down. As @RickMachE pointed out, regen has an impact as well. As others mentioned there are also losses due to heating and the inverters not having perfect efficiency, so measuring from the charger gives a higher kwh value than what the car reports went into the battery.

 

[alexgorod]

I believe all trip data includes regenerated electricity...

I don't know if you replied to my post regarding percentage increase from 89 to 92, but I wasn't driving down a hill, it was definitely a temperature-related change. Bottom line - there is no reason to take these measurements very seriously.

 

[JimmyMachE]

There is even a counter for energy stored in the HV battery called "Energy to empty kWh", which can be read using Car Scanner Elm Obd2 phone app, but even that number fluctuates a lot, so probably just another approximation of energy stored in the battery.

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