Charging (In)Efficiency

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I charged my SE last night. For some reason the Mini app didn’t record how much energy it used but the battery was at 24% when I plugged in and it went to 100%. Temperature was -2C overnight. I didn’t set it to precondition for any departure time.
Going from 24% to 100% if we use 28.9kWh as the total then I added 21.96kWh to the battery. My smart EVSE showed that I’d used 25.52kWh. That’s about 86% efficient.

Looking at the analysis of the charge on my EVSE app it seems to have charged at a max power of 3.6kW despite charge current being set to the max in the car and there being just over 7kW available to the EVSE and no other appliance being on through the night which could have reduced power to the EVSE. We’ve been having some issues with our alleged smart EVSE so I suspect that’s the problem but I’ll need to look into it.
 
SpeedyRS said:
I charged my SE last night. For some reason the Mini app didn’t record how much energy it used but the battery was at 24% when I plugged in and it went to 100%. Temperature was -2C overnight. I didn’t set it to precondition for any departure time.
Going from 24% to 100% if we use 28.9kWh as the total then I added 21.96kWh to the battery. My smart EVSE showed that I’d used 25.52kWh. That’s about 86% efficient.

Looking at the analysis of the charge on my EVSE app it seems to have charged at a max power of 3.6kW despite charge current being set to the max in the car and there being just over 7kW available to the EVSE and no other appliance being on through the night which could have reduced power to the EVSE. We’ve been having some issues with our alleged smart EVSE so I suspect that’s the problem but I’ll need to look into it.
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For whatever bad software reason, the app seems to only load the last charge cycle data after the car is driven.
 
JZ99 said:
For whatever bad software reason, the app seems to only load the last charge cycle data after the car is driven.
Click to expand...
The data is there, it just doesn’t show how much energy was used.
I did do a manual precondition just before we left home and it was still plugged in to our EVSE but the figures stated above were taken before that. I don’t know if that manual precondition messed up the data in the Mini app. Screenshot below.

662532C6-A5D5-4D31-B97D-89DFE7EB21A2.webp
 
JZ99 said:
We are converging on:

L1 60-65%
L2 80-85%
L3 90-95%

Obviously, L3 is best, since the boost and rectification is done internal to the charge station, vs. the car OBC. But you still pay for the loss, via higher kWh rate.
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In cold weather, yes. (as in freezing or below)

Back in Dec with temps around 21c / 72f I got 75% efficiency on the L1 charger (although I stopped before 100%).
Two days later with same temps I got 82% efficiency on the L2 charger (which includes going all the way to 100% and thus includes cell balancing).

I should also point out that my numbers always include the car sitting 2 hours after coming home and before charging window starts.
If you charge immediately after a reasonable length drive the battery will be warm and charge better.
Well, that's the case for DC charging anyway, not sure how much difference it makes on L1/L2.
 
I always put mine on to charge right away and my garage is about 50F right now. Seeing 60ish% efficiency on L1, but I'm not sure it's with worrying about.
 
For info, mine had been sitting on my drive unused for over 24 hours when I began charging on our L2 last night. If I’m charging at home it’s not usually straight after driving the car.
 
Then I guess the battery temperature isn't important for the rate an L2 charger can pump those electrons in, only DC fast charging.
 
Over 100,000 miles, at $0.125 per kWh, averaging 3 miles/kWh at the battery, the difference between 60% and 80% efficiency would represent around 14MWh, which would cost around $1,800. So, it is marginal.

One consideration, for me, is that if I install an L2 charger, the power company will halve my overnight rate. This represents another $2,600 savings. So it will definitely be worth doing.

Summary:

L1: $7,000
L2: $5,200
L2 cheap electrons: $2,600

Savings: $4,400

I'm hoping wire prices go down soon. Also, we will see what Congress does for Federal incentives, as I believe the 30% charger tax credit has expired.
 
I'm calculating about $1.50 difference per full charge (L1: 40Hrs, L2 5Hrs) between L1 & L2 at $0.12/kWH rate & 62 / 82% efficiency. Maybe $150 per year if you drive 12k miles & drive efficiently, so maybe 3-4 years if you can plug the charger into an existing 240 outlet. Maybe an additional 5-8 years if you have to get a new 240V outlet into your garage ( ~$1000? ). I guess that's why I have been living with the 120V charger for the last 5 years. My Fiat 500e is more like 70-75% efficient at 120V 1.5kW, making the payback time even longer. Once I get the SE, that 1.2kW 62% efficiency level 1 charging is going to be an issue getting enough juice into the thing for my typical daily driving
 
JZ99 said:
Over 100,000 miles, at $0.125 per kWh, averaging 3 miles/kWh at the battery, the difference between 60% and 80% efficiency would represent around 14MWh, which would cost around $1,800. So, it is marginal.

One consideration, for me, is that if I install an L2 charger, the power company will halve my overnight rate. This represents another $2,600 savings. So it will definitely be worth doing.

Summary:

L1: $7,000
L2: $5,200
L2 cheap electrons: $2,600

Savings: $4,400

I'm hoping wire prices go down soon. Also, we will see what Congress does for Federal incentives, as I believe the 30% charger tax credit has expired.
Click to expand...

Thanks!!
 
JZ99 said:
Over 100,000 miles, at $0.125 per kWh, averaging 3 miles/kWh at the battery, the difference between 60% and 80% efficiency would represent around 14MWh, which would cost around $1,800. So, it is marginal.

One consideration, for me, is that if I install an L2 charger, the power company will halve my overnight rate. This represents another $2,600 savings. So it will definitely be worth doing.

Summary:

L1: $7,000
L2: $5,200
L2 cheap electrons: $2,600

Savings: $4,400

I'm hoping wire prices go down soon. Also, we will see what Congress does for Federal incentives, as I believe the 30% charger tax credit has expired.
Click to expand...

This is a very helpful calculation! I had to re-read and comprehend this was for 100k miles, and of course costs will most definitely change based on localities, but it provides excellent insight into the cost/benefit of considering installation. I put on 30k miles in 4 years, and would rarely need the speed of a L2 given my daily driving, so perhaps the $1200 to install might not be worth it. Or perhaps wait until we get our second EV and decide on the future of charging down the road? Of course there are places that still have install rebates in place...
 
drdunkyn said:
This is a very helpful calculation! I had to re-read and comprehend this was for 100k miles, and of course costs will most definitely change based on localities, but it provides excellent insight into the cost/benefit of considering installation. I put on 30k miles in 4 years, and would rarely need the speed of a L2 given my daily driving, so perhaps the $1200 to install might not be worth it. Or perhaps wait until we get our second EV and decide on the future of charging down the road? Of course there are places that still have install rebates in place...
Click to expand...

$1,200 is dirt cheap for a Level 2 EVSE install. If you are in California it could be $0.20/kWh (exclude free solar from your powerwall) so it would only take you 10,000 miles to break even.
 
teslarati97 said:
$1,200 is dirt cheap for a Level 2 EVSE install. If you are in California it could be $0.20/kWh (exclude free solar from your powerwall) so it would only take you 10,000 miles to break even.
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You’ve piqued my interest now. I’ll run my numbers and see how it works out. I didn’t think $1200 was that great (just to install 240v + charger) but I’m also a cheap *******… if as good as you suggest then that would be worth it!


Sent from my iPhone using Inside EVs
 
drdunkyn said:
You’ve piqued my interest now. I’ll run my numbers and see how it works out. I didn’t think $1200 was that great (just to install 240v + charger) but I’m also a cheap *******… if as good as you suggest then that would be worth it!
Click to expand...

Costs to install depends on complexity of the electrical systems. Taking from Neocharge's article:
evsecosts.webp

This does not include the price of a main panel upgrade from 100A to 200A but shouldn't be a problem since you already have solar.
 
Thanks for the responses -- I obviously need to do far more research into the installation. The car is probably a couple months off, and I think I'll see what it does/costs with L1 charging. Also, I have a huge fear of electrical work. I got through med school but never really clicked with physics electronics. Go figure. So many people on here are far beyond my grasp of the basics! :( Stick to what you know, right?
 
drdunkyn said:
Thanks for the responses -- I obviously need to do far more research into the installation. The car is probably a couple months off, and I think I'll see what it does/costs with L1 charging. Also, I have a huge fear of electrical work. I got through med school but never really clicked with physics electronics. Go figure. So many people on here are far beyond my grasp of the basics! :( Stick to what you know, right?
Click to expand...
Ha, sounds about right. I could never do med school; I get light headed just hearing about people's injuries sometimes. No way no how. :confused:
 
drdunkyn said:
Thanks for the responses -- I obviously need to do far more research into the installation. The car is probably a couple months off, and I think I'll see what it does/costs with L1 charging. Also, I have a huge fear of electrical work. I got through med school but never really clicked with physics electronics. Go figure. So many people on here are far beyond my grasp of the basics! :( Stick to what you know, right?
Click to expand...
As a doctor, I'm sure you realize that there's never enough time in a day, which is what makes time so valuable. You absolutely want at least a 32-Amp L2 EVSE because you don't want to wait any longer than necessary for your SE to be ready to drive again.

It's not just the charging speed that tips the balance in favor of L2. When it's cold or hot outside, you will likely want to be pre-conditioning the interior of your SE, and this process is less problematic with an L2 EVSE. If you try to pre-condition your SE's interior while L1 charging, it can limit charging, leaving you with a comfy interior but less than a full charge.

Even if you have a second car that could get you to your destination while your SE is L1 charging, you'll start regretting that the second car (even a Tesla, Taycan, or Corvette) is depriving you of the fun you could have had in your SE. That's my completely unbiased opinion :)
 
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