Electricity (kWh) Fuel Consumption and MPGe

[pb]

How would the system change for tracking kWh depending on how/when people stop and record their electric fuel-ups?

That's what we need to determine. Maybe the current system of adding a fuel-up will work perfectly fine as you mentioned. Maybe we could call it a charge instead of a fuel-up and have it work the same way. Maybe that's not an efficient way to do it if you're adding a charge every day. It might be tedious to have to enter a value every time you add a charge. We don't know yet so we're getting info from people who are doing their own EV tracking.

[BDC]

So by "Electric Vehicle Supply Equipment" you basically are saying "a 230VAC power line with a circuit breaker" then?

That is all fine and well but if what you say is true (charger is integral to the car and "smart cable" doesn't display anything) and the above post by DrInnovation is also true (vehicle only displays internal usage), then the Chevy Volt at least does not allow the user to know the charging conversion efficiency.

Is this true? That sounds bogus to me.

[ryogajyc]

pb, I apologize if I'm being dense, but I still don't understand what you are trying to determine. Please give a specific example of two different systems.

BDC, it takes 12.9kWh to fully charge a Volt from empty and it has a 10.4kWh usable battery capacity, so the charging efficiency is 80.6%. It is a simple calculation to divide the charge reported by the Volt by 0.806 to get the actual electricity used.

[pb]

Please give a specific example of two different systems.

Well, there's the per-charge option that you mentioned. In my first comment I mentioned that there could be some sort of monthly option that coincides with an electricity bill statement—that would comprise many charges into one entry. There might be more options, I'm not sure. We're trying to find out how EV owners are tracking their consumption.

[BDC]

That 80.6% value is most definitely not a constant and actually changes significantly. That is what I was originally talking about. How are you tracking the efficiency as it changes?

[ryogajyc]

pb, by two different systems, I meant two different systems of how Fuelly would record the data. Unless I'm missing something, in both those cases, a user would record date, odometer, kWh charged, price/kWh. The thing that changes it the frequency of the log entries, but Fuelly AFAIK is agnostic of that. For example, filling up on gas every day is analogous to charging every day and checking it with the electric bill is analogous to a longer interval of every tank of gas. Presently, I fill up when I'm low on gas, and Fuelly works fine. If I were to fill up and record my gas tank every day, Fuelly would still handle that perfectly fine.

BDC, the 80.6% should be a good average value. It may vary +/- 5% from charge to charge, but a person's average over time should be relatively accurate as well as the aggregate across multiple vehicles. Furthermore, it's no worse than the 10% mileage hit between 100% gasoline and E85, which also is not accounted for by Fuelly. I personally am going use a power meter and I expect those who care more about accuracy will as well.

[pb]

If I were to fill up and record my gas tank every day, Fuelly would still handle that perfectly fine.

That's true. But if you were to fill up every day and record your fuel-ups once/month in aggregate, Fuelly wouldn't work very well. It's not set up for that.

I know it might look simple from the outside to have us add this feature, but I want to make sure we do it right. Tracking kWh is a different beast.

[ryogajyc]

What is the problem with filling up every day and recording once a month?

[pb]

Take a look at this FAQ: Why do I have to fill the tank all the way up every time I buy fuel?

Because Fuelly uses the difference from full to calculate fuel economy for a single fuel-up. Without a full tank to work from, there's no individual MPGs calculated.

[DrInnovation]

Unfortunately, The volt does not display charging efficiency, and the 2011 does not even display internal kWr used, only external apps can see that level of detail.

To mesure the efficiency of the charger I used a kill-a-watt meter measure what it takes to fill from empty-to-full. After a number of averaged cycles i use a formula to convert from battery usage to kw. Was within 2% of actual when I did measurements for a week. My averages using a Kill-a-watt for my car was 13kw for a full charge. (Note the car will use some wall power for thermal management, which is I think the larger amount of the variations. If its very hot it can cool (not common where I live), if its cold it can warm.

I track actual EV milage and amount of battery used per day (using data from Voltstats). I convert that to kWr per day and then once a month I convert to $$ (when I get my electric bill). My car is not on a separate line in the, but the costs are in 2 lines (off-peak and morning rate) and its easy to reallocate costs.

I cannot allocate costs until then since some items change (allocation of fixed costs) with the actual usage.

I would probably enter the montly total and cost together for the month, not