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Discussion Starter · #41 ·
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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.
I often drive 100 miles to friends who only have 120V also. My thought is to install 240V outlet at their place and mine - using an electrician, of course - and then buy one of those 32A portable charging cables that I can use at both places. Right now I have to stop at free public Level 2 charges to supplement the Level 1 charging. I’ve only had the car for 2 weeks. Still trying to figure things out. The dealer essentially knows nothing so you and others have been super-helpful!
 

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I often drive 100 miles to friends who only have 120V also. My thought is to install 240V outlet at their place and mine - using an electrician, of course - and then buy one of those 32A portable charging cables that I can use at both places. Right now I have to stop at free public Level 2 charges to supplement the Level 1 charging. I’ve only had the car for 2 weeks. Still trying to figure things out. The dealer essentially knows nothing so you and others have been super-helpful!
That sounds like a good plan (if you don't mind paying for 2 240v outlet installations).

Yeah, we have a friend who lives 100 miles away too, and I've used my 120 v EVSE there twice (on the i3 - don't have my Solterra yet), but I had to leave the car plugged in the entire time I was there. I've thought about paying her to have a 20 amp 240 v outlet installed so I can use my 16 amp 240 v TurboCord in/near her garage, but the last time I checked her service panel had no open breaker spaces.

She could do a 40/50 amp 240 v in her barn (separate panel) but then the car would have to park in the barn to charge (possible, just not ideal).
 

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Discussion Starter · #43 ·
That sounds like a good plan (if you don't mind paying for 2 240v outlet installations).

Yeah, we have a friend who lives 100 miles away too, and I've used my 120 v EVSE there twice (on the i3 - don't have my Solterra yet), but I had to leave the car plugged in the entire time I was there. I've thought about paying her to have a 20 amp 240 v outlet installed so I can use my 16 amp 240 v TurboCord in/near her garage, but the last time I checked her service panel had no open breaker spaces.

She could do a 40/50 amp 240 v in her barn (separate panel) but then the car would have to park in the barn to charge (possible, just not ideal).
Interesting that you have a similar situation. I guess I need to find out capacity and cost info. Thanks again for all your help.
 

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Discussion Starter · #46 ·
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.
Hello. I have a new question: After now understanding that the car doesn’t charge at the same rate while charging, i.e. that it charges fast until it reaches a certain percentage and then slows down considerably as it approaches full, I’m wondering if the formula is affected by this variable. Thanks.
 

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Hello. I have a new question: After now understanding that the car doesn’t charge at the same rate while charging, i.e. that it charges fast until it reaches a certain percentage and then slows down considerably as it approaches full, I’m wondering if the formula is affected by this variable. Thanks.
It likely only begins to "taper" (when charging at either 120 or 240v) when it reaches about 95%... so if you don't charge it that far, you'll never see the rate drop.

The formula will work from the point you start charging until it stops, or reaches about 95% - whichever comes first.

Edit: I have the charging curve for my i3, but won't for my Solterra until it arrives in a week or two. I imagine the charging curve for AC is similar. I'm sure there are people here who can share the shape of their charging patterns.

Ignore the bumps, that's my home heating system turning on and off.

Slope Rectangle Font Line Plot
 

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The charging curve for AC Level 1 and Level 2 charging is probably pretty flat, but I will test that out in the next few days and report back.

I picked up my Solterra about 12 hours ago.

The charging curve that is very much not flat is DC Fast Charge (DCFC). That's the one everyone is complaining about.

Assuming a flat curve for home (L1 or L2) charging should be fine, up until at least 90-ish%. but again. testing will reveal more.
 

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The charging curve for AC Level 1 and Level 2 charging is probably pretty flat, but I will test that out in the next few days and report back.

I picked up my Solterra about 12 hours ago.

The charging curve that is very much not flat is DC Fast Charge (DCFC). That's the one everyone is complaining about.

Assuming a flat curve for home (L1 or L2) charging should be fine, up until at least 90-ish%. but again. testing will reveal more.
Be sure to do a full 100% charger first at L2 to completely balance all the cells. Otherwise, that could prolong your DC charge at the end while it completes that. I know my Kona EV worked that way. It actually had intermediate balancing intervals, I think around 90%, where it would pause for a while, sometimes as long as 10 min. They said it was to do cell balancing and a battery health check. This was implimented after the battery fire scare. Better to brick a car when a bad battery is detected than risk a fire. I suspect that Toyota is pretty conservative and carefull, too, with their charging schemes to protect the battery.
 
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