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2021 Ascent Limited; 2023 Bolt EUV Premier w/S&S, SC
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Interesting!

Sense has a similar solution, but it doesn't monitor individual circuits (it uses AI which works - sorta). I've been using that for almost 5 years now, it has yet to identify my EV charging as a distinct "device" - despite its unmistakable usage pattern (the "bumps and spikes" are other devices turning on and off during the night):
Add the Flex Sensors to your Sense! I purchased them before I had my 240V circuit installed and the Qmerit (thru Chevy Bolt purchase) installer put them in my panel for me. They used to just be for monitoring solar, but Sense updated them so you can monitor a specific 240V circuit (or one or two 120V) or a separate panel.

My 2023 Bolt EUV can take 11.5kW (240V/48A), but I am using the 240V/32A EVSE that comes standard with it (boo, Subaru, for only including 120V EVSE). I pay $0.15/kWh here in the Milwaukee, WI area, so I entered that into Sense to get costs along with usage. Here's my current status, along with last week's and last month's usage. The final image was yesterday, when I charged it from 90% to 100% before a trip. The second peak is when I conditioned the cabin while plugged in, before leaving. I've only seen the taper when charging to 100%. I don't know if it's slowing down to protect the battery or doing cell balancing at that time.

I've grown frustrated with Sense (I've had mine for over 4 years) that it's not getting smarter, but I have energy-monitoring smart plugs for some important things, and it's proven helpful. Mostly, it's just me learning more useless, interesting information! Before I got the 240V installed, I used a Kasa plug to monitor the 120V.

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Discussion Starter · #24 ·
kWh usage per charge. kW is a measure of power, how quickly energy is transferred. kWh is how much energy is transferred.

To compute kWh per charge, multiple 120 (volts) x ___ amps (8 - 12, whatever) x hours plugged in, divided by 1,000. Multiply that result by about 1.1 to account for efficiency loss.

So, at 8 amps, that would be 120 x 8 / 1000 x 1.1 or approx 1.06 kWh per hour of charging time.

At 12 amps, it would be..... (1.5 x that figure) .... approx 1.59 kWh per hour of charging time.

Multiply either figure by the per kWh price the person pays and you'll have your answer.

At $0.10/kWh, that would be either 10.6 cents per hour or 15.9 cents per hour.

Edit: bottom line, you're not going to owe them a lot of money, unless their per kWh price is really high.
For 10 hours of charging that would be $1.06 or $1.59 at 10 cents/kWh. For 20 hours, $2.12 or $3.18.
If this formula works, why would I need to buy a device? Perhaps a device is more accurate but wouldn’t this formula provide a good estimate?
I noticed the charging choices in the Solterra are: Max, 16A, 8A. Does that mean that if the outlet can supply 20A, my car can use the full 20A???
 

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If this formula works, why would I need to buy a device? Perhaps a device is more accurate but wouldn’t this formula provide a good estimate?
I noticed the charging choices in the Solterra are: Max, 16A, 8A. Does that mean that if the outlet can supply 20A, my car can use the full 20A???
That might be the case (I don't know what the max rating of the provided "convenience charger" is), but that would have to be an outlet on a dedicated circuit with a 30-amp breaker. Most 120v outlets are just 15 amp (on 20-amp breaker).

I'm pretty sure the convenience charger doesn't come with a 20-amp plug, otherwise it wouldn't fit in a 15-amp outlet.

A 20-amp outlet looks like this:

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Versus a 15-amp outlet:

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Discussion Starter · #26 ·
That might be the case (I don't know what the max rating of the provided "convenience charger" is), but that would have to be an outlet on a dedicated circuit with a 30-amp breaker. Most 120v outlets are just 15 amp (on 20-amp breaker).

I'm pretty sure the convenience charger doesn't come with a 20-amp plug, otherwise it wouldn't fit in a 15-amp outlet.

A 20-amp outlet looks like this:

View attachment 1606

Versus a 15-amp outlet:

View attachment 1608
Thanks. Very helpful.
 

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2021 Ascent Limited; 2023 Bolt EUV Premier w/S&S, SC
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I noticed the charging choices in the Solterra are: Max, 16A, 8A. Does that mean that if the outlet can supply 20A, my car can use the full 20A???
I'll add one important note here. Since charging an EV is a continuous load, it's important that you don't draw more than 80% of the circuit's rated capacity. For example, on a 20A circuit, you must limit draw to 16A. 15A circuit, 12A max. This holds true for for 240V circuits, too, so if you want to charge at ~32A, you need a 40A circuit. (Solterra has a 6.6kW charger in the car, which is 27.5A at 240V, but it seems they draw more like 30A from the wall.)

The EVSE and the car talk to each other to set a max current draw, but nobody talks to the circuit (breaker, wire, receptacle), so it's up to you to make sure you aren't overloading the circuit. Some EVSEs (Tesla) have interchangeable NEMA connectors where the EVSE will set the max current draw based on which connector is used, but that's not typical.
 

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Discussion Starter · #29 ·
So, if I’m understanding this correctly, when charging from 120V outlet, I should set the car charge at 16A but when charging at a public Level 2 charger, I should set it a “max”. Is that correct?
 

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So, if I’m understanding this correctly, when charging from 120V outlet, I should set the car charge at 16A but when charging at a public Level 2 charger, I should set it a “max”. Is that correct?
That is actually a little confusing. Depends on whether it is a 20A or 15A circuit. You need the 20A if you want to charge at 16A. If you only have the standard 15A circuits, you need to change the setting to 8A. There is no 12A setting on the Solterra which is odd, as that is the max setting you can charge on 15A circuits. Most other EVs have 8 and 12A settings, not 16.

But yeah, for 240V public L2 chargers set it to max. The 240V setting is separate from the 120V setting.
 

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So, if I’m understanding this correctly, when charging from 120V outlet, I should set the car charge at 16A but when charging at a public Level 2 charger, I should set it a “max”. Is that correct?
Generally, no. Don't charge at 16A!

If the EVSE (the little 120V charging cable) which was supplied (in North America) with the Solterra had been constructed with a 20A plug on it like this:

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(notice that of the two straight blades, one is 90º from the other)

then it would be rated to carry 16A (80% of 20A) continuously, and would safely support 120V 16A charging.

Since the supplied North American charging cable only has a 15A plug on it, it's only rated for 12A (80% of 15A), and thus you should not charge at 16A.

Now why didn't Toybaru supply a charging cable with the proper 20A connector? Mostly because most North American household outside outlets are only rated at 15A and the 20A plug would not mate and the customer would be very dissatisfied.

Even if the wiring happened to be rated at 20A, and the breaker at 20A, and the outlet was either a 15A or a 20A rated outlet, that plug on the charging cable is only rated for 15A (12A continuously).

*Note there is a 16A and an 8A setting for the car's charge limiting.

That's unfortunate in that there isn't a 12A setting, which would, in North America, provide the greatest charging current available for the typical household circuit (in good condition and properly installed).

But with old breakers, crappy aluminum wiring (in some) and worn out outlets in many houses, I do think that 8A is the maximum safe continuous current drain for many hours.

The included EVSE cable is just for the convenience of being able to charge when you first get the car, until your real 32A (or better) 240V EVSE is installed.

Or when you are traveling and staying at someone's house without an EVSE and want to charge in a pinch.
 

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Discussion Starter · #32 ·
That is actually a little confusing. Depends on whether it is a 20A or 15A circuit. You need the 20A if you want to charge at 16A. If you only have the standard 15A circuits, you need to change the setting to 8A. There is no 12A setting on the Solterra which is odd, as that is the max setting you can charge on 15A circuits. Most other EVs have 8 and 12A settings, not 16.

But yeah, for 240V public L2 chargers set it to max. The 240V setting is separate from the 120V setting.
This all is very confusing but I’m sure I’ll figure it out in time - with your help! Very appreciated!
My house has original electric from 1950’s so I guess it’s standard 15A and I should change the car setting to 8A. It took over 30 hrs to charge my car from 45% to full with the setting on “max”. Any chance the change in setting can help? 30 hrs is ridiculous.
 

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Generally, no. Don't charge at 16A!

If the EVSE (the little 120V charging cable) which was supplied (in North America) with the Solterra had been constructed with a 20A plug on it like this:

View attachment 1609


(notice that of the two straight blades, one is 90º from the other)

then it would be rated to carry 16A (80% of 20A) continuously, and would safely support 120V 16A charging.

Since the supplied North American charging cable only has a 15A plug on it, it's only rated for 12A (80% of 15A), and thus you should not charge at 16A.

Now why didn't Toybaru supply a charging cable with the proper 20A connector? Mostly because most North American household outside outlets are only rated at 15A and the 20A plug would not mate and the customer would be very dissatisfied.

Even if the wiring happened to be rated at 20A, and the breaker at 20A, and the outlet was either a 15A or a 20A rated outlet, that plug on the charging cable is only rated for 15A (12A continuously).

Notice that there's a 16A and an 8A setting for the car's charge limiting.

That's unfortunate in that there isn't a 12A setting, which would, in North America, provide the greatest charging current available for the typical household circuit (in good condition and properly installed).

But with old breakers, crappy aluminum wiring (in some) and worn out outlets in many houses, I do think that 8A is the maximum safe continuous current drain for many hours.

The included EVSE cable is just for the convenience of being able to charge when you first get the car, until your real 32A (or better) 240V EVSE is installed.

Or when you are traveling and staying at someone's house without an EVSE and want to charge in a pinch.
Your post made me go out to the garage to check the car supplied EVSE. And it is indeed just a regular 15A outlet plug, not the 20A one.(y)
 

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Discussion Starter · #34 ·
This all is very confusing but I’m sure I’ll figure it out in time - with your help! Very appreciated!
My house has original electric from 1950’s so I guess it’s standard 15A and I should change the car setting to 8A. It took over 30 hrs to charge my car from 45% to full with the setting on “max”. Any chance the change in setting can help? 30 hrs is ridiculous.
P.S. It was on “max” because I had no knowledge. From what I’m reading, maybe “max” was a dangerous setting to use at home. Again, all very confusing but I’m learning! Subaru should offer a class with charging details. Manual is insufficient.
 

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72.8kWh battery pack.

Starts at 45% SOC (state of charge).

We want to charge it to 100%. 55% of 72.8kWh needs to be supplied to the battery pack. That's 40kWh.

Assume 10% charging loss in the car's on-board AC charger.

We need to supply about 44kWh to fully restore the charge to 100%.

It does look like the supplied charging cable tells the car to limit to 12A and the car probably actually does limit to 12A when set to "Max" (even though the other settings are 8A and 16A, it appears that the on-board AC charger is able to actually limit to 12A).

Assuming 12A, at 120V, thats 1.44kW charging rate.

Divide the 44kWh needed by 1.44kW and you are left with a result of 30.5 hours.

That's basically what you received.

Yeah, you maybe traveled 120 miles, maybe in 2 hours, and now you need to charge for 30 hours to restore it.

This is why a 32A 240V EVSE is pretty much a necessity for 90%+ of drivers.

Divide the 44kWh needed by 6.6kW and you are left with a result of 6.7 hours. Now that's decent. If you are plugged in at the office and work an 8 hour shift, you're fully charged, at home, an overnight charge instead.

Obviously the supplied 120V charging cable isn't going to supply your needs.
 

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When my Solterra arrives (estimated for next week), I will plug the supplied EVSE into my Kill-A-Watt meter and play with the various 8A, 16A and Max settings to see what the actual current draw is.

I am somewhat hopeful that it will draw about 12A when the car is set to Max.
 

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Discussion Starter · #37 ·
72.8kWh battery pack.

Starts at 45% SOC (state of charge).

We want to charge it to 100%. 55% of 72.8kWh needs to be supplied to the battery pack. That's 40kWh.

Assume 10% charging loss in the car's on-board AC charger.

We need to supply about 44kWh to fully restore the charge to 100%.

It does look like the supplied charging cable tells the car to limit to 12A and the car probably actually does limit to 12A when set to "Max" (even though the other settings are 8A and 16A, it appears that the on-board AC charger is able to actually limit to 12A).

Assuming 12A, at 120V, thats 1.44kW charging rate.

Divide the 44kWh needed by 1.44kW and you are left with a result of 30.5 hours.

That's basically what you received.

Yeah, you maybe traveled 120 miles, maybe in 2 hours, and now you need to charge for 30 hours to restore it.

This is why a 32A 240V EVSE is pretty much a necessity for 90%+ of drivers.

Divide the 44kWh needed by 6.6kW and you are left with a result of 6.7 hours. Now that's decent. If you are plugged in at the office and work an 8 hour shift, you're fully charged, at home, an overnight charge instead.

Obviously the supplied 120V charging cable isn't going to supply your needs.
Thanks for explaining why it took so long to charge and also why my house didn’t catch on fire when setting was set to “max”:)
 

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The 120v EVSE could work for you if you don't drive a lot on any given day. If parked/charging for say 12 hours per night, that's 1.44 x 12 = 17.28 kWh.

Divided by 1.1 (efficiency loss) that's 15.7 kWh delivered to the battery pack.

Divided by 72.8 kWh (battery pack size) that's just shy of 22%.

If you don't drive/use more than 22% on a typical day, you can keep up with your daily usage (say 80% down to 58% every day) by charging at 120v for 12 hours every day. But a safer option would be to install a dedicated 240v outlet for a 240v EVSE (assuming your service panel can support it - sounds like maybe not?). Whatever you decide, please consult with a licensed electrician.
 

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2023 Subaru Solterra with Technology Package, Platinum White with Two-Tone Black Roof
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When my Solterra arrives (estimated for next week), I will plug the supplied EVSE into my Kill-A-Watt meter and play with the various 8A, 16A and Max settings to see what the actual current draw is.

I am somewhat hopeful that it will draw about 12A when the car is set to Max.
Yeah even if the car is set to max or 16A, the provided EVSE is probably limited to 12A so that is all the circuitry in the EVSE will provide to the car. It won't matter if the on-board charger is asking for more, the EVSE won't give it. Someone who has one already, I am sure the provided EVSE has a label on it with how many amps it can provide. Take a picture and send it please.
 
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