How to measure how many KWHs in a fill-up?

[mikecarlton]

Can anyone tell me if the Leaf, or Carwings or some EVSE can give me a simple "you used X kwh to recharge your battery" on each charge cycle?

I've long tracked miles/gallon and $/mile on my existing car -- just a matter of noting the odometer mileage on the receipt when refueling, then entering the data into a spreadsheet or an app.

I'd like to get a simple kwhs used reading, add my price/kwh and calculate the same thing for the Leaf. But I've been searching all over these forums and it seems like there's no easy answer. I even asked the Nissan people when they did their drive tour back in December and they were clueless.

 

[DaveinOlyWA]

no but there are ways to track your charge from the wall which is what u want when running costs. obviously a dedicated EV meter is the way to go, but i am using 110 volt charging only at this time with a Kill a watt meter. its a device that measures charge, currrent, voltage, etc. but only works for 110 volts.

a few others have EVSE's that measure the charge used as well but have an issue that all have a vampire charge that runs even when the car is not plugged in. i remove the vampire issue by unplugging mine when not in use.

 

[planet4ever]

Yes, Kill-A-Watt is great for 120v. For a 240v EVSE the answer is TED (The Energy Detective) unless you have a really fancy charging dock. Use the Google search option here to look for TED. You'll see a lot of references spread through a number of different threads.

Ray

 

[mikecarlton]

Thanks for the info.

I'm just really surprised that such a basic report can't be generated by the car's charger -- I figure it should know how much it is consuming. I'm annoyed that I have to spend $200+ to install a TED device just to figure out how much a charge costs me. I'll be installing a 240V evse, so kill-a-watt won't work.

 

[Boomer23]

Several of us have actually enjoyed installing and using the TED. Its software tells you a lot about how you use power in your home and the graphing displays can be really useful. Mine identified some shading that I was getting on my solar panels late on winter days and prompted me to top a tall bush that was creating the shade. I've found that using the TED really fits well with my EV enthusiasm and helps me to predict the impact of my future charging on the LEAF on my household energy costs.

That said, each TED installation is different, dependent on how your power panel is set up, whether it has room for the TED components that need to be housed inside the panel, and possible interference issues for the communications between the MTUs inside the panel and the TED gateway inside your home. Some people have struggled with these issues, but most have resolved them.

 

[walterbays]

It would be useful to have, even if it were only something approximate that you could get from CarWings afterwards. If for example I could say that I had drawn about 8 kWh on Monday and 12 kWh on Tuesday, charging at work, then I could reimburse the company. (Throw $2 in the coffee fund?) We're not talking big bucks here, but the principle of the thing could make the difference between having recharging available and not. E.g., the GSA ruling that prevents federal employees from recharging at work seems to hinge on paying for the electricity consumed.

 

[DaveinOlyWA]

i also think TED is well worth the money. i also think that your power company should pitch in. our company used to reinburse us for several home energy upgrades or partially fund an upgrade or mod. they also allowed us to provide suggestions. i wonder if they would feel this a worthwhile project? even a $25-50 rebate to offset some of the cost would be cool

 

[kolmstead]

I'm not as thrilled with TED as some others are. Mine keeps losing track of the date and time, and it sometimes forgets all recorded data also.

For the average user, I think the Carwings electrical consumption report would be more than adequate. Yeah, it ignores charger inefficiency, but it ought to be good for estimating the cost of a fillup to within ten or fifteen percent. It says that my daily commute uses about 10 kWh, and that's roughly what TED says that I put back in. And Carwings is free for a few years.

-Karl

 

[LEAFer]

Would love the TED functionality ... but I don't see the ROI with it ... JMHO.

And, yeah, I agree, CarWings should give us some more info on charging session history/energy use from the wall.

 

[garygid]

To avoid over-drawing from the EVSE, the LEAF should be measuring the current "from the wall" (from the EVSE, essentially the same thing) as it charges. However, it might not measure the voltage, and thus not know the power.

However, there might be sensors for the current and voltage (thus power) going into the Battery Pack.

 

[DaveinOlyWA]

The transformer in the middle will mess up any reading from the wall to the car

 

[garygid]

What transformer in the middle?
There is no transformer that charging power goes through, I believe.

 

[GeekEV]

Would love the TED functionality ... but I don't see the ROI with it ... JMHO.

And, yeah, I agree, CarWings should give us some more info on charging session history/energy use from the wall.

Me too. It would be a cool, geeky thing to have, but I just don't see how it *really* helps me enough to justify the cost.

 

[garygid]

Is the Efergy wireless E2 ($140) or Elite ($120) the same as TED?

 

[DaveinOlyWA]

the box on the charging cord which would only apply to the 110 volt is where you need to track power in. the EVSE mod proposed in another thread should have a counter that is relayed to the car somehow but does not. disappointing. now with a KAW its easy enough to monitor but would be nice if the car did it for us

 

[garygid]

It is easy to measure the 120v power with the easily-available Kill-a-Watt (KAW) plug-in meter.

Measuring 240v power, at the plug, is more difficult, partly because there is no "standard" 240v plug.

 

[wescom]

This is easy to do if you have a BLINK Ecotality charging unit!!!

The unit computes cost per charge. You have to enter the cost per kWh.

So simply enter $1.00 as the cost per kWh!!! Then the "cost" for the charge will be the actual number of kWh used in the last charge.

Works perfectly.

William Moerner

 

[TickTock]

Depending on the desired accuracy, you can get pretty reasonable accounts just by multiplying the time it takes to charge by 3.7. If you have it text you when charging is stopped and start on a timer, it is really easy. Just look at the time you got the text and subtract the time you started then multiply by 3.7 kW (after converting the time to decimal - i.e. 4:45=4.75, etc). This 3.7 scalar is "typical" value for L2 chargers but may vary a little (although it seems to be pretty consistent from what I've read here). If you want more accuracy, borrow a friends ampmeter and measure your current and voltage at the circuit breaker during the charge and multiply to get your own scalar (should come close to 3.7kW). This should get you within 5%. If you want better then that your options are 1) spend the $200+ or 2) learn to read your service meter, shut off all breakers in the house except the EV charging circuit, and record the before and after values (of course this isn't something you would want to do daily).