Measuring charging efficiency

Hi all.

My ZS has done about 12k km, and is averaging 16.5 kWh per 100km (6.1km/kWh, or 3.8 mi/kWh). That's calculated from the energy in as measured by my EO charger. I've not reset my cumulative trip counter for a while, and that says I'm using 14.4 kWh per 100km. So this tells me that my charging efficiency is about 87% (14.4/16.5), i.e. I'm actually getting to use 87% of what I put in. I was expecting to lose in the order or 10%, so that's fairly close.

Is this a reasonable method?
Has anyone else done this calculation?

Gonzo

gonzoB said:

Is this a reasonable method?

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I think so, though it relies on the accuracy of two different measuring systems.

Also, it's not exactly "charging efficiency" that it's measuring, because you're counting pumps and all the auxiliary loads and the DC-DC converter losses, as well as just charging losses. Is cleaning your windscreen or using headlights a "loss"?

Even so, it's a useful figure to know. I suspect I've seen a similar calculation before, with similar results, but can't quickly find it.

I have noticed this also, and this is something that is never reported.

If there is a 10% loss, and i (offcourse) have to pay for this, then the price of running an EV, goes up by 10% when it comes to electricity.

So if you pay ½ pound for a KWh, in reality the price is 0,55 pounds for one kilowatt in your car.

I wonder if the measuring of how much power i got, is based on the "into" the charger or "out of" the charger.

I mean, do i pay for what comes out of the wire, or the power that is fed into their charger.

I do all my costings on what goes INTO the charging cable - I use the meter in my wall charger.

I assume the cumulative trip meter on the car measures ALL of the energy drawn from the battery, not just the power needed to run the traction motor, so that would include the HVAC, etc. Losing 13% for getting the energy into and out of the battery is not the end of the world, but I was wondering if that loss is different depending on where you live. I'm in AUS, so the temperatures here are warmish. In the UK, for instance, I would expect the losses to be higher, as the battery performance is affected by temperature.

Gonzo

gonzoB said:

I do all my costings on what goes INTO the charging cable - I use the meter in my wall charger.

I assume the cumulative trip meter on the car measures ALL of the energy drawn from the battery, not just the power needed to run the traction motor, so that would include the HVAC, etc. Losing 13% for getting the energy into and out of the battery is not the end of the world, but I was wondering if that loss is different depending on where you live. I'm in AUS, so the temperatures here are warmish. In the UK, for instance, I would expect the losses to be higher, as the battery performance is affected by temperature.

Gonzo

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The wall charger is AC so there will not a be a lot of losses there, as it essentially just does the communication with the car to tell what it is capable of, and then the car sets up the charge and does not take more than the charger tell's it can handle (Basically "What it can handle" = What rating the cables and fuses are)

So on AC home charger, the losses will be in the inverter in the car, that takes 110/220 volt and converts it into 400 Volt DC.

On the rapid DC chargers the charging circuit sits inside the box with the screen and cable, and in that situation the losses are inside that charger box.

That box is essentially the same as the one in the car, it is just vastly more powerfull, as it can deliver loads of amps, which the onboard charger can not.

But i would offcourse also assume that i am paying for the electricity going INTO the rapid charger and not, the electricity i get out. Someone has to pay for the loss inside the box.

Maybe in the future, the "petrol stations" will begin to compete on, whose chargers have the least amount of losses in their chargers. How much loss it has, is totally dependent on how good the manufacturer is to design and build the electronics inside the inverter.