How accurate is the Miles/ KwH measurement

[Fokmg]

From the start of the year I decided to accurately measure the energy used/ miles travelled and have been suprised to discover the miles/Kwh measurement appears to be 10% out?

To calculate my readings I charged the car to 100% plus equalisation (this was my zero point) . I reset the Miles/KwH gauge and drove the car for the whole month and recorded every recharge (always done at home). At the end of the month I recharged the car to 100% and completed my monthly equalisation.(this was my end point)
The car travelled 426.7 miles (mainly short dark and wet journeys ) the car registered 3.10 Miles/Kwh for the months use.
I used a total of 152.28 Kwh of electric this equates to approx 2.80 Miles/Kwh even allowing for the fact that maybe 1.5Kw were consumed during the equallisation charge and some energy is lost during the recharge process the difference is nearly 10% more than I would have expected

This is rather disapointing and misleading as the car is not travelling as far on a Kwh of electricity as it claims

The car is always driven in Eco Kers 3 mode and drives on hilly narrow lanes most of the time

Has anyone any thoughts ideas or similar experience

Car Mg5 ev SR

 

[Jomarkh]

I would of thought that 10% in losses would be about right.
How many charges and to what percentage did you go to during that month?

 

[rpannell]

I suspect that you are confusing KWh as measured by you house meter or charger and KWh as stored in the battery. The car is showing how many miles it will travel on a KWh of stored (battery) electricity. To obtain 1KWh of battery electricity, you will need around 1.1 - 1.15 KWh of house electricity due to the losses. The losses are in the AC to DC converter, heat produced in the battery and cable losses

 

[Fokmg]

Hi I would have done about 14 charges. Charging range would have been between 35% to a a max of 80% most between 40% - 60%. Min ammount would have been 2KWh max would have been 23KWH. ( Obviously the final charge was to 100%. and included equalisation )
Interested to know where the losses occur and what what is the best way to charge.
I use a Zappi charger either eco mode (if it is sunny) or fast charge (7KW) .
Much appreciate your comments
I wonder how many people know that 10% of the electricy can gets lost during charging?

 

[rpannell]

Most people ignore the extra cost due to losses. So if you are paying 12p per KWh and your car tells you it does 3 miles on this, the cost per mile, due to losses, will be more like 4.4p - 4.6p per mile rather than the 4p per mile. The losses on AC (home charger) are greater than the losses on DC (rapid charging) as 1KWh from a rapid charger is after the AC to DC conversion losses. On AC, 10-15% losses are typical whereas on DC it will be more like 5-8%.
For losses, it makes little difference whether you charge at 7KW or 2.3KW on a granny.
The losses in the battery, in making the chemical change required to store the electricity, end up as heat. This is why you will sometimes hear the battery cooling fan working during a rapid charge.

 

[Petriix]

I calculated that it wastes at least 1kWh every time you charge to full. Charging losses are typically over 10%.

My experience is that the miles per kWh figure as reported by the car uses a bayesian average which tends towards 3. In the summer mine was clearly under reporting by about 15%.

 

[5teep]

So what you are all saying is that there's no such thing as free energy and that all charging systems have losses because there's no such thing as 100% efficiency...

 

[smokie]

Did anyone ever do this complicated stuff when they drive an ICE? I know I didn't , and I still dont.

 

[AnonymouseDriva]

. The losses on AC (home charger) are greater than the losses on DC (rapid charging) as 1KWh from a rapid charger is after the AC to DC conversion losses. On AC, 10-15% losses are typical whereas on DC it will be more like 5-8%.

Are you sure? I would have thought that the power being delivered to the rapid charger is still generally AC (unless it's coming from another battery, and even then I'd put a fiver on it being converted to AC and back again). The AC/DC conversion is just done in the charger instead of the car, and you can be fairly sure the supplier won't be paying for that lost energy.
I would expect that the metering is on energy into the charger before all the AC/DC conversion etc (so the energy you actually used to charge the car) and not just on the DC going out.
I've only used rapids a couple of times but it sounded like they had fans in there to help disperse the heat whilst charging, so you'll be paying for the fan consumption as well as the energy lost to heat. (although I doubt even the meatiest of fans will make that much difference...)

Did anyone ever do this complicated stuff when they drive an ICE?

yeah, but it was easier. (or at least it would have been if I wasn't buying by the litre and reading economy as miles per gallon...). Plus, you didn't need to worry about those fractional pennies - it's all about the pounds with an ICE!