Running costs

[hughindevon]

A quick update and or correction. As the rapid charging is DC, perhaps the on-board inverter is not involved in high power charging? I don't know if it is or not. My Zappi is sending 230 volt, 50 Hz AC so it definitely uses the on board inverter to charge the car battery so my overall running costs will be affected by the inverter efficiency.

Just for general info. Just done a 4 day, 3 night excursion to Cornwall. Only 184 miles but managed 4.1 miles/kWh which was pleasing. About half of the mileage was on dual carriageway (at a cruise controlled 56 mph) and the rest on mainly rural roads.

[CrowSysE243]

https://static.nhtsa.gov/odi/tsbs/2021/ ... 7-0001.pdf gives a good description of the MEB charging system used by hte Enyaq. It gives the inverter efficiency as 94%, but this may be at the rated 11kW and may be reduced if charging at 7kW. My estimate of the overall efficiency for energy stored into the battery when charging at home at 7kW is 91%. This includes the inverter and the electrochemical reaction in the battery. The inverter is not involved when rapid (DC) charging, however the electrochemical conversion efficiency will still be a factor.

[ricky10]

The Octo Aid app is quite handy. I can see that my average price per KWh on days with no EV charging is 22p and my overall average in a month (including EV charging usually two or three times a month) is just under 20p.

That’s not as good as octopus tracker which has been average 16p for months and months. Even there are days you get 5p per unit.

How do you make sure the car only charges during low rate periods? Do you get 16p all day, or is it varying throughout the day depending on national demand?

Yeah typically 16p all day that’s the point of tracker tariff. It’s averaged over a month period.

When there is a super cheap day which you can predict by looking at Agile price 24/48hrs ahead, you can send manual reading to octopus therefore charge the car Donal your stuff needed to then send another manual reading to lock in the cheap rate.

[spinna1969]

Tomorrow’s rates are a jump like.

[ricky10]

Yeah, no sun, no wind, colder temp tend to swing the rates higher. Also trouble in mid-east gas prices going up too.

Also worth noting that tracker daily average price is usually lower than the agile daily average. I don’t know why. But it just is. Around 10%

[hughindevon]

Very interesting to see some details on the HV system, thanks for the link.
Your figure of ~91% grid to miles efficiency is helpful too. I have been intending to start collecting data from my Zappi charger and from the car to try and develop an estimate of the charging efficiency. The Zappi side of the data is easy, the car not so straightforward. Ideally I would like the reported miles/kWh figure to exclude the power used by heating, air con, etc. Does this figure exist anywhere? I doubt it does without attaching a dongle to the can bus. I do actually have a wi-fi dongle that I have never used. I bought it for a previous car but sold the car before ever trying it. Do you know if there is any analysis software for the Enyaq (or, more likely ID4)?

Regards, Hugh

[CrowSysE243]

My data does include heating and air conditioning, etc, however we have not used A/C or heating much after the first few weeks once I worked out how to set the car up the way I wanted it. I have estimated efficiency 2 ways. The first way, including all charging since getting the car, is based on comparing the total energy input, from all chargers used, divided by the total mileage driven up to the most recent charge and adjusted for any differences in percentage charge, with the car estimate of long term average miles/kWh. As I have not used any preconditioning before driving yet and the car consumption estimate is affected by heating/cooling while driving, this seems reasonable but does include a small amount of DC charging on the 450 mile trip upt to Scotland and over to Northern Ireland, starting at 100% and then AC charging when we arrived. I have also estimated efficiency by comparing the sum of the differences between the total accumulated charge reported in CarScanner after and before AC charging with the sum of the energy used by the chargers. In principle this will be a better estimate of charging efficiency but the overall figures for the >4000 miles driven so far is only a few tenths of one percent. I have not noticed any data available using car scanner that would allow heating/cooling power to be excluded when it has been drawn from the battery.
I don't know of any particular analysis software for the Enyaq or other MEB cars.