That seems kinda low unless the battery required a lot of temperature conditioning ...

 

I might be wrong, but once the Bolt reaches the charge limit, it uses about 3-4 kWh more doing the advanced analyses on the battery. So, in fact, the loss in charging is about 12-15% - which can be normal - and the rest is the battery checks that are running afterwards.

 

I thought that battery balancing and conditioning only happened at 100% SoC -- and even then, not every charge. Maybe I am wrong ....

 

Energy is measured in kWh, not kW. Your efficiency is low based on those numbers. But what is the basis for the 45 kWh - is that your whole house usage? If so, it's not a good measure of just charging.

 

is that when the car says 'fully charged', but my evse shows that it is still charging?

 

Yes. And it is "working" for about 4 hours, as I saw people reporting here this behaviour. This is why I said in another message, to implement the delayed charge and set the finish charging time around the time you are ready to leave the house.

 

You talking about kWh? I've never seen "KW" usage data on PG&E's site or paper bills for residential plans. I'm also on PG&E.

I only have 100 amp service, so I can't even do 30 kW, let alone anything above that. 100 amps * 240 volts = 24,000 watts = 24 kW. Bolt can't pull that much over J1772 either.

I don't know what year of Bolt you have but none have higher than 48 amp on-board charger, 240 volts * 48 amps = 11,520 watts = 11.52 kW, so you can't pull above 11.52 kW over J1772 on Bolt.

 

Are you charging via L1 (110v) or L2 (220v)? 110 is less efficient than 220 and has more losses. Other than that, losses of up to 15% is typical on L2 (220v) when considering possible conditioning, battery balancing, 12v battery maintaining, and up-conversion from the onboard charger. There's a lot of variables at play that can make it more or less, but just know that ~15% is typical for L2, even higher on L1

 

We don't have 110 or 220 volts in the US. It's 120 or 240 at homes. 208 volts is common for commercial power in the US but likely uncommon for single family homes.

 

Yes and no. It's commonly called both 110 and 120 (and 220/240) because the voltage can be a range anywhere between. My home has 115v measured at the outlets and 230v at the panel, where the commercial properties I work have 208v 3-phase that ends up reading as 115v and 202v when measured on a volt meter.

Perhaps we should say 115v and 230v to average it out. 😛

 

Not sure I'd trust the electric company.

The EPA energystar site has some numbers for EVSE's. I know when I buy electrons at CP their energy number is 10% or so higher than mine.

10kWh is a lot of waste but I'd need better metrics.

The dotted line above is when my electric doesn't transmit data.

 

Preconditioning the cabin can also have a big impact of efficiency, especially with short trips. You can easily burn 1 to 1.5 kWh preheating the cabin. More than that if you live in a really cold area and/or preheat the cabin to a higher temp. If you drive 200 miles, that extra 1.5 kWh doesn’t make a huge difference, it if you drive 5 miles to work and 5 miles back, that would probably use about 3.5 kWh in cold weather… so if you add 1.5 kWh of preconditioning, that’s basically bringing your efficiency from 2.8 miles per kWh down to 2… or a loss of about 30% efficiency! That same scenario with a 100 mile drive only results in a 4% drop in economy.

 

You've been corrected by others, regarding kW vs kWh, so I won't continue. However, I question how you measured that "... the car took on 30-35kWh,"? I do understand you may have been able to detect the energy delivered from PG&E to the EVSE, as you stated "... it took 45kWh to do so!".

 

Thanks, guys, for your replies. Sorry, I carelessly used KW instead of the more accurate KWh. And my math may be a little loosy-goosey.

I got my numbers from this chart. It clearly shows when the car is charging. Yes, it includes what the house is using too, but that's only maybe 500 Wh. When the car is charging, it draws 8KW/hr (8KWh, right?) (This chart only shows part of the charge cycle, the rest continues on the next day's chart) I just added up the approximate 8KW/hr times the 5-6hrs it took to charge. The car was showing about "half full" before charging. So, that's where I got "the car took on about 30KW" part. And yes, my EVSE is 240V, 40A. Am I way off?

 

Thanks, guys, for your replies. Sorry, I carelessly used KW instead of the more accurate KWh. And my math may be a little loosy-goosey.

I got my numbers from this chart. It clearly shows when the car is charging. Yes, it includes what the house is using too, but that's only maybe 500 Wh. When the car is charging, it draws 8KW/hr (8KWh, right?) (This chart only shows part of the charge cycle, the rest continues on the next day's chart) I just added up the approximate 8KW/hr times the 5-6hrs it took to charge. The car was showing about "half full" before charging. So, that's where I got "the car took on about 30KW" part. And yes, my EVSE is 240V, 40A. Am I way off? View attachment 66761

"kW/hr" would be kilowatts divided by hours, a nonsense unit. kWh is kilowatts times hours. The reason it's like this is that kW is a unit of power, so power * time (kW*h = kWh) is a unit of energy.

As to your math, I have to agree it's too imprecise to draw any conclusions. If you must know your charging efficiency, you'll need an EVSE that can precisely measure energy supplied to the car

 

You say your car put 30 or 35kWh into the battery and your estimate is PGE sent your car 8kW (maybe) for 5-6hrs, which would result in 40 or 48kWh. That means somewhere between 63% (30/48) and 88% (35/40) of the energy went into the car's battery.

That's already a wide range but to get these #s you're making a lot of assumptions and estimates which means the true numbers might be different still. For example, I would be surprised if your house only uses 500wh over 5-6 hours, and if you charged to full, the car tapers the charge rate at the end so it's incorrect to assume a constant rate.

If you really want to check the efficiency of your charge, you probably need more reliable numbers for what flowed past the EVSE (some will actually keep track of this) and what ended up in the car's battery. A bluetooth dongle + car scanner app would let you see exact SOC% or even kWh in the battery to know how much was added.

 

KW/hr would be average power usage over an extended period of time kilowatts per hour

a convoluted way of saying killowatt hours

it hurts my brain thinking about the units


i think the OP has way more appliances drawing power in his house than he thinks

 

1000*watt*hour
/ Can be is divided by but also count/per.

My favorite is when they get lb feet and feet pounds argument.

 

My pet-peeve (besides kWh, kW/h, kW, breaks and brakes) is using "mph" for a speed. That abbreviation implies a multiplication (m x p x h), when in fact the calculation is a division (mi/hr).

 

As to your math, I have to agree it's too imprecise to draw any conclusions. If you must know your charging efficiency, you'll need an EVSE that can precisely measure energy supplied to the car

You can get gadgets that can be connected ahead of your EVSE to measure the KWhr consumed by the car. I have an old Sagnamo analog meter in series with my Clipper Creek EVSE that I read and record on or about the first of every month. Dunno why I care, but I do it anyway.

 

Kilowatt is a rate. Kilowatt-hour is an amount. How fast water comes out of my garden hose is a rate. How much water comes out is an amount.

 

Your charging numbers are too imprecise to come up with a good conclusion. To check your actual numbers, you'll need to measure it at the car and the wall. You'll lose some energy from the box to your car due to heat loss, but that's maybe 1% max. If you have. 40 amp breaker, you're drawing about 32 amps, so maybe around 7.6 kW through the wall into your car. You'd be surprised at how much energy your house uses in the middle of the night depending on a lot of factors, such as running a home server, having a large fridge, garage freezer, or A/C running.

Anyway, I digress. The easiest way to measure your draw is to get a OBD dongle and run a program off your phone to see the actual numbers being pulled into the car and from the car into the battery.

Running my LELink and EngineLink app, I usually see anywhere from a 90%-95% efficiency, depending on weather and battery SoC on L2 and about 97%-99% on DCFC.

The LELink is only about $30 and works with ABRP for routing with SoC and charging functions. I'd highly recommend it if you do any sort of long traveling.

 

Anyway. Not sure we really know how much power is going back into the battery. For practical purposes we have to add up all the costs of power going out of the breaker service a 240VAC evse.
Each EVSE can take power and they take more power when plugged in not charging. EPA site has advertised numbers for that.
My little 60-70 a day takes about 39,829,438.8 foot-pound to recharge.

 

My little 60-70 a day takes about 39,829,438.8 foot-pound to recharge.

But how many horsepower-hours is that?

 

Darn! I put my slide rule away.

 

Pvillerob left us.

 

Nope, still here. Some of ya just got off into the weeds....😄

 

I measured the charging efficiency on my Bolt and got 80% efficiency. At that level, you should have gotten 36KW of charge into your batteries if you used 45KW line energy. So you aren't far off. I don't know what technology GM uses for their chargers, but if it is a series regulator, the numbers you read are probably accurate. In order to get more efficient, you would need what is called a switching regulator and that is more expensive to manufacture. So it doesn't take a rocket scientist to figure out why GM didn't go that way. They aren't paying for your electrical power. I don't like government interference, but that is what is needed to force the EV manufacturers to use more efficient chargers. After all, our government did that to force car manufacturers to optimize miles per gallon of gasoline.
Dave W

Thanks, guys, for your replies. Sorry, I carelessly used KW instead of the more accurate KWh. And my math may be a little loosy-goosey.

I got my numbers from this chart. It clearly shows when the car is charging. Yes, it includes what the house is using too, but that's only maybe 500 Wh. When the car is charging, it draws 8KW/hr (8KWh, right?) (This chart only shows part of the charge cycle, the rest continues on the next day's chart) I just added up the approximate 8KW/hr times the 5-6hrs it took to charge. The car was showing about "half full" before charging. So, that's where I got "the car took on about 30KW" part. And yes, my EVSE is 240V, 40A. Am I way off? View attachment 66761

 

I havent looked into it but the charger in the car has to be some form of a switching step up power supply, because it can charge from 120VAC or 240VAC and the battery is 380 to 400VDC

so it has to be some form of PWM pumping up inductors or an LC filter circuit

and here is the catch: most meter circuits assume a pure sinewave and measure the average voltage and current. But when the load is being pulsed or chopped you need an RMS meter to get an accurate reading

RMS meters cost 3 to 4 times as much, like a Fluke 87 compared to a Fluke 83.

Most meters are not true RMS.

 

How do you measure exact energy usage from PGE to calculate this? Do you use the meter or do you log onto you account online?

 

I was using my energy usage numbers as reported by PG&E via my online portal.

 

I have a few different ways to look at my energy usage while charging the Bolt.
PG&E offers a graph of blocks, and if I click on a block, I can see the draw for that hour, 6.07 kWh, for example.
That's for the whole house, in my case, which runs about 400 watts doing nothing, but might have some other usage from time to time.
I have a Tesla Powerwall,which should show house draw in agreement with PG&E, 6.0 kW.
I have a JuiceBox, which lets me see the energy being supplied to the Bolt. 5.6 kW That's the only worthwhile measurement.
5.6 / 6.04 =93% That looks like a 7% loss, but it's not. It isn't going to the car at all, except for the drop between the meter and the EVSE. I have measured that, but I don't have it handy. The rest of that loss is idle draw in your house. You could look at the other nearby PG&E blocks to guess what that might be.

I also have an OBD reader. That could give me the starting and ending levels of kWh in the battery in ABRP.
I can also use the OBD and CarScanner to view the AC draw and the DC provided to the battery during a charge.
The Carscan is from some other date. It shows AC of 24.6*240 = 5904, and DC of 15.5 * 347.5 = 5386.25
5386.25 / 5904 = 91%.

 

While charging the Bolt, which lets me see onboard charger AC volts with an OBD and CarScanner:
PG&E Smart Meter 243.8 volts, ([23.4 amps], 5.7 kW)
JuiceBox 238 volts, 23.4 amps, 5.57 kW
OBD CarScanner 236 AC volts, 23.6 AC amps, 5.57 kW
OBD CarScanner 391 DC volts, 13.6 DC amps, 5.32 kW

Circuit loss from house to charging outlet (243.8 - 238) * 23.4 = 135.72 watts
From Juicebox to Bolt charger (238 - 236) * 23.4 = 46.8 watts
DC charger ratio to house input AC 5.32/5.7 = .9333

This is on a 30 amp dryer circuit, with 80 feet of #10 AWG.

This was after the car had been charging for a few hours, so the wires were heated. The first few minutes might have lower loss.

 

I'd put a better meter on the car evse.

However if the electric company said you are using more then maybe I'd not complain. Maybe you are getting power at a lower rate.