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Discussion Starter #1
Just got my Juicebox 40Pro installed today by an electrician. Was wondering if 25 miles per hour charging is more energy "intensive" than 4 miles per hour charging...saw the temp go up to 120 F in the EVSE while it was charging.
Does anybody know: If time wasn't an issue, would 110V cost less kWh to charge than 240V?
 

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240 could be less efficient because it warms up the battery faster, and might require active cooling during the charge.
 

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Data on the Volt shows the included L1 cord is less efficient.
Not sure how that translates to the Bolt, but I'd lean towards similar results.

Earlier this year was, I part of a data logging trial for 3 months, a study done by FleetCarma. On my 2012 Volt, here's what I observed:

Miles driven: 4,863
Electric %: 100%

Total charge events: 269
Level 1 charges (120V): 78
Level 2 charges (240V): 191

Total energy (kWh): 1,242
Total charger loss (kWh): 160 (12.9%)

Level 1 energy (kWh): 385.8
Level 1 charger loss (kWh): 55.68 (14.4%)

Level 2 energy (kWh): 856
Level 2 charger loss (kWh): 104.1 (12.2%)
http://gm-volt.com/forum/archive/index.php/t-45617.html
 

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Yes, electrons flow more efficiently, the higher the voltage. That's why the lines coming out of Grand Coulee Dam are carrying 500,000 volts, so they can carry it long distances with relatively lower line loss.

Also, the adjunctive fans, pumps, heating/cooling processes take a relatively bigger bite out of the available energy at 120V that they do when charging at 240V.

But, say your overall efficiency from wall outlet to battery pack is 85% at 240V. If it dropped to 83% (SWAG) at 120V, would you notice the time difference? I wouldn't unless my OCD neighbor was in my garage with his stop watch.;)
 

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I have never heard the battery-cooling circulation kick in when charging at 240V in my "partially air-conditioned" garage like I have when DCFCing outside on a warm day. Is it just me, or do others notice the same? I am not "pre-airconditioning" the interior while still "on the plug", but I plan to try "pre-warming on the plug" when Winter comes.
 

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Discussion Starter #7
I've never even heard the battery conditioning come on (it always says 0% on the energy usage screen). I'm sure that's going to change in winter.
The reason I ask the question of 110v vs. 240v is that I have solar panels. On a good day, I can easily make enough power to feed the car using 110v and still not use any grid power. But with 240v I'll have to take some from the grid.
I realize it's all a matter of accounting, an electron is an electron no matter where it comes from, so that whatever power I feed into the grid I can just take out later with charging the EV. (My utility doesn't have TOU for residential customers)
 

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I have never heard the battery-cooling circulation kick in when charging at 240V in my "partially air-conditioned" garage like I have when DCFCing outside on a warm day. Is it just me, or do others notice the same? I am not "pre-airconditioning" the interior while still "on the plug", but I plan to try "pre-warming on the plug" when Winter comes.
it's possible that DCFC requires more cooling just because you're sending a lot more power into the battery. that heats things up.
 

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it's possible that DCFC requires more cooling just because you're sending a lot more power into the battery. that heats things up.
I agree. I was simply saying that you are not "spending" any more electrons cooling the battery at 240V than you are at 120V. The solar panel question is the true tipping point. If davids wants to charge without taking from the grid, maybe 120V is still the way to go. davids: Can you charge only when the sun is shining, or can you "store" the energy to put into the car at a later time? Would you partially charge when sunny, and then change plugs and "top off" at night?

Does your power company pay you to "feed into the grid" or is that gratis? (Many utilities allow you to "donate" electrons, but will not pay you for them.)

We also do NOT have time of use differential billing.
 

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The reason I ask the question of 110v vs. 240v is that I have solar panels. On a good day, I can easily make enough power to feed the car using 110v and still not use any grid power. But with 240v I'll have to take some from the grid.
I realize it's all a matter of accounting, an electron is an electron no matter where it comes from, so that whatever power I feed into the grid I can just take out later with charging the EV. (My utility doesn't have TOU for residential customers)
I'm assuming you have net metering? If so, I'd still charge at night when demand for power is low, and feed your solar excess to the grid during the day when it's needed most. 240v charging is more efficient and will save you a slight amount of money.
 

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Discussion Starter #11
davids: Can you charge only when the sun is shining, or can you "store" the energy to put into the car at a later time? Would you partially charge when sunny, and then change plugs and "top off" at night?

Does your power company pay you to "feed into the grid" or is that gratis? (Many utilities allow you to "donate" electrons, but will not pay you for them.)
No, I don't have a home battery yet. I think what you suggest is exactly what I'll do on the weekends when I don't really need the car and as long as the sun is shining enough for solar generation.
If and when home batteries are much cheaper, I'll be able to store the power during the day and feed the car at night. There's power loss when going thru batteries so it may not be the best solution for efficiency.
And if they take net metering away, I'm going to buy a home battery and get a generator for the winter.
 

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I ran the numbers on my 2018 Bolt with the included L1 charger (plugged into a Kill a Watt meter), and with my recently acquired 240V Jekayla L2 charger, which continuously displays accumulated kWh, charging current, charging kW, and other parameters. The L1 charged at 85% efficiency. That is, for every 100 kWh through the charger, the car accepted 85 kWh in the battery. (Just for illustrative purposes; I know that the battery only accepts a max of 60 kWh.) The L2 charges at 95% efficiency. The L1 is now in the trunk, for travel use when nothing else is available, and I use the L2 exclusively.
 

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Just to add a data point, my Bolt EV is charged at my apartments' parking lot at 220V 32A (7kW) and I have not seen battery cooling kicking in. This adds about 40km (25mi) per hour, so I think it's similar to the 240V charging that's talked about in this thread. Charging efficiency has been hovering around 90%.
 

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I too have never heard the conditioning fan kick in while charging (Level 2), but I charge almost exclusively between 11 PM and about 5 AM. I have heard it kick in when I have my Bolt parked and the air conditioning cranked up on a warm day.

I do wonder if Level 3 (DCFC) charging is more efficient. The power use for battery conditioning should be at most a couple of kW, which isn't much. The DCFC inverter (built into the charger) may be more efficient than the Level 2 inverter built into the Bolt. In any case, it's likely DCFC will reduce battery life if the Bolt's drive battery is anything like the drive battery in a Tesla.
 

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Op- if you have "net metering" for your solar production, it would be beneficial to charge at 240V since it's slightly more efficient, faster and you could charge any time you desire.

We're not talking huge % points difference between 120v and 240v efficiency, but you will actually use less kWh overall to charge at 240v. It all depends if you're on "net metering" for your solar....
 

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If you have solar, it's best to use the energy you use. Why sell your excess solar production at 2-3 cents a KWh and buy it back to your for 16 cents at night when it is produced using fossil fuel plants.

Using the energy you produce also ensures minimal system loss as it could take 3 KWh produced at the power plant to get you 1 KWh in your garage.
 

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Yes, electrons flow more efficiently, the higher the voltage. That's why the lines coming out of Grand Coulee Dam are carrying 500,000 volts, so they can carry it long distances with relatively lower line loss.
Higher voltages are used to reduce power loss because of power line resistance, not because electrons flow more efficiently. Power dissipation/loss is proportional to the square of current multiplied by resistance (I*I*R). For the sake of simplicity, assume that a 1 mile long cable is 1 ohm.
If you transmit 1200W at 120V over 1 mile there will be 10A flowing in the cables and it will dissipate 10A*10A*1ohm=100W.
If you transmit 1200W at 240V over 1 mile there will be 5A flowing in the cables and it will dissipate 5A*5A*1ohm=25W.
 

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To answer the original question, 240V charging is more efficient than 120V charging. The Bolt battery voltage is typically around 96*3.0V=288V at empty (3.0V is a safe estimate) to around 96*4.1V=394VDC at full. 120VAC is about 120*1.414=170VDC when rectified. 240VAC is about 339VDC when rectified. Those voltages need to be converted to the battery voltage using a DC-DC converter, and that converter is most efficient when the input voltage is near the output voltage. The farther the input/output voltage ratio is from 1 the lower the DC-DC converter efficiency, in general.
 

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If you have solar, it's best to use the energy you use. Why sell your excess solar production at 2-3 cents a KWh and buy it back to your for 16 cents at night when it is produced using fossil fuel plants.

Using the energy you produce also ensures minimal system loss as it could take 3 KWh produced at the power plant to get you 1 KWh in your garage.
Here in VT, we are paid the residential rate (same rate as wat we pay the utility) for any excess solar generation fed back into the grid on a grid-tied system. When I put my system in, the State was giving a bonus incentive of an extra 5.3¢/kWH for every kWH I generate, whether it is fed back into the grid or I use it myself. That bonus incentive is locked in for the first 10 years of operation of the Solar PV system, after which it goes away, and I drop back to just getting the retail rate . (Before I put my system in, the bonus incentive 6¢/kWH incenvtive, and has been slowly phasing out ever since. I'm guessing it may have phased all the way out by now.
 
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