Electricity Draw of Charger When not Charging

power factor.
@jerrymildred can add a definition.

 

Power factor . . .

 

I plugged in my P4400 Kill-a-Watt and with only the EVSE plugged into the wall and not the vehicle. Note, I waited for the EVSE to run it's check and go to sleep (30 seconds) before taking these readings.

Volts = 122.5
Amp = 0.12
Watt = 0.00 - 0.01 but no higher. I waited but it's between .00 and .01.
VA = 14
Hz = 59.9
PF 0.06
kWh = 0.00

PS, I read it again after plugging into the car with a departure schedule set and there was no draw. Same readings as above.

 

ah, i was only off by 100%

 

I would expect the power usage of the EVSE to be not that much more if the car were plugged in but not charging. All that would be active would be a simple circuit monitoring the data line to the charger in the car, to see if the car wanted to be charged. The power mains to the car are disconnected by a relay when not charging, so zero is going through them. I would expect that it would take years to accumulate even a few pennies of electric usage.

And a desktop computer taking 120 W in sleep mode does not sound right. "sleep" mode is where the monitor and hard drive are turned off, and the CPU is put into a low-power sleep state, and the there is only enough power usage to maintain the RAM memory. I would expect it to be more like 5 or10 W.

 

Mark,
Was your test with the supplied EVSE from Toyota, or another brand? I just looked at my Kill-A-Watt again, and am still getting the same readings as earlier.

Just for giggles I tested my battery powered toothbrush. It indicated .7 Watts.

 

Yes, the one that comes with the vehicle.

 

hmm... maybe one of the guess o meters is off?

 

For various technical reasons, watt meters tend to be considerably less accurate at low power levels and low power factors, so it's not surprising that the readings with various Kill A Watt meters may vary. It is also possible that the EVSEs themselves vary somewhat in their standby power use.

My Kill A Watt meter shows the EVSE drawing 0.5 watt when not charging. But that is based on a current of only 0.02 amps (about 1/7500 of the full scale current of 15 amps), thus it is very sensitive to small errors in the measurement. These errors are likely to vary from unit to unit.

The main takeaway is that 0.5 watt is only one kilowatt hour (kWh) every 2000 hours, which is 83 days (edited from my original post, which erroneously said five years!).

 

I have my Prime charging on a circuit with power monitoring and logging. (TED5000) Let me first mention that it's really really cold outside. Like 5 degrees Fahrenheit.

Every 1/2 hour or so, for about 7 minutes, the car draws about 1.4 kW. And no, I don't have the heat on. The manual does sort of refer to this in a oblique manner, stating that when it's cold, the car will do stuff, don't ask. But in further reading, the manual explains that there is a traction battery heater. It seem reasonable to assume that this is what I am seeing. If it's cold enough, the traction battery heater will run automatically for three days after you plug the car in. It only runs if plugged in. (Note that if you live in Canada or Alaska, the rules are slightly different.)

I think, (from the manual), that if you use the charge timer, the traction battery heater will hold off until it's time to charge. So using the timer in cold weather seems like a good idea. I don't know if it shuts off again after the charge, I'll have to check. (something that might matter on weekends.)

You can also turn the traction battery heater off completely. I'd imagine that there is a penalty on the electric range, but depending on the length of the commute, maybe that's still more efficient than heating the battery electrically.

As far as what the car draws when not charging, and not cold, it does seem like it's next to nothing. However, I'd like to watch over a longer period when the traction battery heater is not active.

 

If a circuit breaker does its job and never works after an overload or short trips it, it has done its job. Thankfully, they typically last for 10 years or more when used as intended. I have worked on "jobs" where power was sourced without a current interruption device at all. Just clamp onto the residential side of the can and drop an extension cord. Once you have done it a few times its easy.

 

PF= Power Factor. Mine says unity when charging. Unity = Power Factor of 1. Even so, keep in mind the car utilizes the 12v battery when plugged in to control the charge of the traction battery. Toyota suggests unplugging when not charging however most people charge overnight (in the manual). Kind of a catch 22 there if you ask me. I guess Toyota prefers the car not to be plugged in when it is not expected to charge (say for a week or so). Also the cost of a 12v battery is pricy but probably not as expensive as not using the Li-ion traction battery over the long haul with gas savings. Although one might have to do a $/kWh comparison for their area against gasoline. I guess it all depends if one wants to save on emissions vs costs.

 

I doubt that a battery charger would produce a power factor of 1. It might get close if it contained PF correction circuity that was very sophisticated. Maybe good PF correction is what makes these charging units so costly. If so, it is money well spent.

 

Power meter is measuring the grid not what I’m drawing. One can’t measure the PF of a device unless it is the one of only two part, generator and power use device.

No, it most likely isn’t a PF correction device charger. I think it is just a safety device, when it is unplugged it won’t provide full current, only some very small amount to prevent serious shock hazard.

 

Half a Watt. Wow... my GE microwave uses 1.5 Watts just to display a green zero on its LCD.

 

1.5 watt for a green LCD is quite a bit, how old is your microwave?!? LED is much more efficient at producing light than LCD. The charger display is most likely LED not LCD like in your microwave.

 

*shrug* Maybe 15 year old GE model, I guess, I never really checked.

 

A 1.5W draw == 13KWh/year -> $1.50/year @ my current rate of $0.12/KWh...
Or the equivalent of two full charges of your prime...

Not a lot but if you have 100 of those little vampires around the house, it can add-up.

 

That’s right it can add up