Monthly Electricity Cost/MPG Equivalent

[edatoakrun]

My original statement, however, was stating that my TOTAL efficiency for 2 charging events (one to 100% and another one NOT to 100%), considering everything, was about 82%. Someday I'll repeat the experiment but strictly to 80% charge and see what the delta is.

And couldn't you begin a second charge session, from 80% to 100%, and determine the total efficiency rate, for this charge period?

Sorry, but I can't seem to see the answer to those questions, from your results posted above.

I often charge for periods of time from "80%" about a half hour, or 1 additional bar, to match maximum charge, also allowing maximum regen efficiency, for my (large initial descent) route.

Doesn't seem to be much loss of charging efficiency (as crudely measured by proportional time required to add kWh) during the `80%-90% charge session.

Is that shown by your results?

 

[lpickup]

And couldn't you begin a second charge session, from 80% to 100%, and determine the total efficiency rate, for this charge period?

I could if I wanted to, but I've only been in the situation once since I've owned the car that I've been at 80% and needed to top off. Plus, and I think the data shows it, there is no taper off until the last 15 minutes (or less), representing the last 0.68 (or less) kWh, which is only about 3% of the battery capacity. So I suspect that if I had better data it would show a steady charging rate all the way up to at least 95% with a taper after that point.

I often charge for periods of time from "80%" about a half hour, or 1 additional bar, to match maximum charge, also allowing maximum regen efficiency, for my (large initial descent) route.

Doesn't seem to be much loss of charging efficiency (as crudely measured by proportional time required to add kWh) during the `80%-90% charge session.

Is that shown by your results?

Not directly, but the data does show that it's only in the last 15 minute block that it tapers off. The 80-90% range would charge at "full power".

 

[DaveinOlyWA]

The rate of charge does not taper off until the last 15 mins?. Wow that would be great.

 

[edatoakrun]

"lpickup"... the data does show that it's only in the last 15 minute block that it tapers off. The 80-90% range would charge at "full power".

I thought maybe that's what you meant, but it doesn't seem to match my observation, that you get 1 bar, and and (at least) near 1 kWh, from a half hour of charging at 80%, but it takes much longer to go to 12 bars, and 100%.

If you watch from your LEAF sign in page, the last "10 minute" estimate to full charge, seems to invariably take near half an hour.

This, more or less, matches my memories of similarly long "10 minute" dash-indicated periods, from last May, when I was sitting in my LEAF waiting for a full 100% charge, to make the two 90+ mile long legs, for my drive home.

 

[dgpcolorado]

This method doesn't account for losses in charging (~85%), but it will be MUCH MORE accurate than your method (and easy!).

Right, so just take the final kWh you get and divide by 0.85 to get the electricity used from the wall. There, now you have a more accurate method.

And while I more or less agree with the 0.85 factor, if you frequently charge to 100% you should lower the factor slightly. I just did a short term test on my LEAF comparing the in-car readings with my EVSE's readings and found the factor was between 0.81 and 0.82, however I did one charge to 100% and one to less than 100% during that test, which accounts for my slightly lower reading.

Another thing to consider is preheating or precooling while plugged in. If you never do that it is moot, but I preheat frequently in winter and that makes a significant difference in wall power usage versus what the car uses from the battery while driving. I put in a DaveinOlyWA style wall meter to track my power usage so I could get accurate numbers.

 

[DaveEV]

The rate of charge does not taper off until the last 15 mins?. Wow that would be great.

It starts to taper in the last 30 minutes from what I've seen. It takes 90 minutes to go from 80-100%.

Since you're charging at 12A, it probably won't start tapering until the last 20 minutes or so.