It is true that level 2 240 charging is slightly more efficient, and you use less electricity to fill the car faster. I think it may have to do with heat loss is less on level 2. What he said is true, but a matter of degree, it is modestly more efficient so over the long run you would use less electricity.

This says it averages to be 5.6% more efficient, but moreso when topping a car off at 4kw or less draw, in which case it is 13% more efficient, or moreso depending on certain temperatures:

https://ieeexplore.ieee.org/document/7046253/

For me, I upgraded to two 240 outlets to save recharge time, but come to think of it, since most days we are refilling about 5kw on the batteries of our two volts at a time, I guess it does make a noticeable difference. We probably average 10% less usage on level 2. We are also standard rate users.




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True - When charging L1, the cooling system runs for a larger percentage of the charge time (and the charge time is more than doubled) and the BMS time at the end of the charge cycle also takes more energy than if you were using L2. From what I've read over the years, the 10% savings figure for L2 appears to be a realistic difference

Don

 

There have been a number of posts on the efficiency of L2 vs. L1 charging. As stated by the other two posts there is in fact a slight electricity "discount" by using L2. You probably won't notice a huge difference in your total power cost but it is a couple cents cheaper per charge. Aside from the BMS running less often, it also allows more power to be put into the battery for charging while also cooling/heating the battery during those times. Electronics seem to suffer less electrical losses due to heat and other inefficiencies when powered at higher voltages. I believe it only amounts to a few percent. This is where the argument as to whether spending a few hundred dollars to have a dedicated 240V line and L2 charger really is much of a money saver. If time is a major concern for you to be able to charge quickly, then yes it's worth it. However it would take years to realize a monetary savings for paying and installing L2 if you are perfectly fine just charging for 8-12 hours on L1.

 

Most properly conducted engineering/scientific studies show that the advantage to 240 vs. 120VAC charging is about 2.5-3% improvement in efficiency. That number can be slightly higher if you charge for only short periods of time, but most people do not charge their cars in that manner.

Reference: https://www.energy.gov/sites/prod/files/2016/06/f32/Vermont Case Study.pdf

 

Many partial charges count as "charge for only a short periods of time". I typically charge 2-4 times a day, not just once, and at least half of those are for about 15-20 minutes, depending on whether it's winter.

 

When charging, you are also activating circuitry within the car, which can draw several hundred watts - This draw is the same for L1 or L2, but since L2 is more than twice as fast, that draw is for much less time

One of those losses is that you are powering the DC to DC converter to charge the 12 volt battery and that converter is running all the time you are charging, regardless of whether you're using L1 or L2. I don't know the exact figures for the Volt, but with my Mitsu, the associated 'losses' to all other circuitry is between 500 and 600 watts, largely due to the DC to DC converter. Assuming the Volt is similar, that means for L1 charging at 12 amps, (1440 watts) 500 of those watts are not going to charge the traction battery, so it would only be getting 1,440 minus 500, or about 940 watts. When charging L2 again at 12 amps (2,880 watts) the traction battery is getting 2,380 watts.

2,380 watts is way more than twice as much as the 940 watts it's getting when L1 charging. Again, I'm not sure what the losses are for the Volt . . . . maybe they are less, but they are still there and they are the same for L1 and L2 and since L2 is more than twice as fast, you're not 'wasting' those watts for nearly as long when using L2

Don

 

In that case, one would waste over 4kwh (500w x (13 - 4.5)hrs) for each L1 charge which is significant but the math doesn't appear to work out:

13 hrs at L1 to the battery only -> .940 x 13 = 12.2KW (too low should be about 15KW)
13 hrs including "losses" ---------> 1.44 x 13 = 18.7KW

4.5 hrs at L2 to battery only -----> 3.3 x 4.5 - 14.85 (seems right)
4.5 hrs including "losses" ---------> 3.84 x 4.5 = 17.28

For L2, I'm using 16A at 240V = 3840w

 

Thanks for the info guys. I much better understand what he was getting at now. Probably not a financial savings (given the cost of an L2 charger), it's probably still worth it for quick charge convenience since I already have the right circuit in my garage from an old dryer hookup.

 

JayVolt: you are absolutely correct - saving 3% on your electricity costs will take a LONG time to pay off the cost of a L2 charger. You are fortunate though that you do not also have the added cost of also requiring a 240V circuit. The GM EVSE unit can actually run off 240VAC (by adding a special adapter) and that would then be able to charge your vehicle at 12 AMPS - 240VAC, not quite up to the 16A or a proper L2 charger, but worth considering...

 

Thanks for informing me of this! I just went down a long rat hole of long and technical threads with many caveats and permutations of specs about this. High voltage stuff is above my pay grade, so here's my ask, if someone could kindly tell me what the easiest route to getting there is:

• 2014 Volt
• EVSE pictured here: https://imgur.com/a/IFlOIpp
• NEMA 10-30 (I think?) 240V outlet in garage pictured here: https://imgur.com/zpCibF3
• Want ability to charge 240V in garage, and still have 120V standard plug capability when I'm traveling (pigtail adapter?)

Is this all I need? https://www.amazon.com/Parkworld-886344-Household-Receptacle-Adapter/dp/B078PHY3ZJ

 

https://gm-volt.com/forum/showthread.php?239225-Upgrade-2015-EVSE-to-120-240V

Appears only the 2013 would work (with mods) on 240v

I have a gen2 but did not want to use the factory EVSE with 240v. I called clippercreek and the tech advised against it. It may work for a while but was not designed for continuous 240v and any surge could damage it. So, I ended up with a used ebay clippercreek for $250ish and keep the 120v EVSE in the trunk when traveling.

CC also sells used recertified EVSE's for $300 or you could buy an amazinge, also made by CC for $219 (1/2 the warranty)

I would stay away from the Duosida EVSE's

That nema 10-30 is outdated and could easily be replaced with a 14-50 or 14-30 for < $10, adapters are over $50

 

Thanks for this info - great advice. I'll look into those models. And yeah, that outlet is surely outdated, it was put in when the house was built in 1965 Tested out clean though when I had an electrician over to check out something else and had him look at it. I'll probably swap it out for a modern outlet box (and relocate it to a more accessible spot) and buy a reasonably priced L2 charger from your recommendations.

 

Do all the testing in cooler temp so the I^2*r is not a big factor
With faster charging the car has to remove the extra heat using 2 cooling systems.
ie battery and electronics.

Even looking at the power curves for home computer systems power supplies the 240 Volts ac units are a bit better than the 120 Vac units.

 

My garage has a 240 V 50 A nema 14-50r (receptacle) (I don't have a Tesla, but this is what Tesla uses for home adapters which is why I have this particular receptacle in my garage)

I built this adapter plug cable for my 240 V 3.8 kw rated charge cable (the attached image).
The purpose of fusing is to protect the wire.
In the main breaker panel there is a 50A breaker, and wire that will carry 50A continuous to the receptacle.

If you use an adapter to go from a 30A or 50 A breaker'ed circuit down to a 20A circuit, you need some new fusing to protect the wires downstream.
So in the middle I installed a custom box with two 20A fuses, one for each hot leg L1, L2.

The small plug shown in the picture matches the charging cable and is a Nema 6-20r (NEMA Straight Blade 20 Amp, 250V Power Cord Plug)

 

If you use an adapter to go from a 30A or 50 A breaker'ed circuit down to a 20A circuit, you need some new fusing to protect the wires downstream. So in the middle I installed a custom box with two 20A fuses, one for each hot leg L1, L2.

That is absolutely the correct way to go about it, but I fear many 'amateur electricians' are ignoring the fact that fuses and breakers are based on wire gauge and too big isn't safe - You could burn down your garage or house. If you have a 50 amp outlet, you should never plug anything into it which uses wire smaller than 8 gauge - Fuses and breakers are sized to protect the WIRE and not the load you may plug into the circuit

If you intend to run a 16 amp EVSE with 12 gauge wire from your 50 amp outlet, you must have 20 amp fuses in the circuit to protect it

Don

 

Always good to have a subpanel in the garage. I put one in myself (with permits and inspections to keep it legal and fire insurance valid) when I renovated the house (had to go along bedroom floor for a ways so carpet had been ripped up before I put in hardwood floor),. I have a 20 amp 230 Volt circuit for my L2 charger that came with the car (it was initially for my 240V air compressor that I now trade off on) and a 30 amp 240V circuit that I use for the old wall oven that got moved to the garage when I upgraded to a new one in the kitchen (that I use for curing VHT painted parts and powder coated parts down the road). This can be used down the road for EV if I get to that stage. These days every home should have a similar subpanel in the garage in the increasingly likelyhood of the EV age. It will make your home easier to sell in the future as more and more people will be looking at this as a requirement kind of like expecting to see a dish washer in the kitchen.

 

The fuse in the breaker box for this circuit is 30A. Since nothing else is on this circuit would it make the most sense to change this out to a 20A fuse in the panel? Or still need to have an electrician put a sub panel in the garage (or in-line fuse in the charger cable)? It seems the panel fuse change would be simpler but I’m not an expert on this stuff.

The problem I have is, if someone sees there is a 30A receptacle in your garage and goes to plug in, then they expect it to be ready and rated for 30A.

Another thing to consider, if you replaced the garage receptacle to the correct 20A receptacle (is your EV plug a Nema 6-20?), and used a 20A breaker in the breaker panel, then the wires would be safe, and everything downstream of the receptacle should be good too.

Summing up, a new 20A breaker in the breaker panel replacing the old 30A one, and a new 20A receptacle for the wall outlet plug that replaces the 30A receptacle. Perhaps this is a more cost effective approach that you were looking for?

 

Doesn't the EVSE have a fuse? So, you're saying the whole 120-240v conversion thread where everyone is making pigtails should have included in-line fuses, since presumably a 14-50 box, is protected by a 50amp fuse.

 

The idea being in the conversion thread, if the only thing you plug into the pigtail has a fuse shortly after the plug? You feel like you are pretty much covered? Or was this even discussed?

In my case, I actually have 2 of these pigtail adapters (slightly different versions), but in 2 of my 3 charging scenarios, I have a heavy duty extension cord with no fusing available until later in the circuit. The Volt 120V charging interface that came with the Volt does have some fusing, but I don't know if my 240 V EVSE cord does or does not have a fuse (with the pigtail fusing, I don't care). My custom EVSE for my EV conversion has no over current protection until you reach the input of the car where L1,L2 breakers are located just past the charge port.

 

Some of the fixed losses in the Volt (regardless of 120V or 240V) are things like pumps to circulate coolant through the battery charger (where the spare tire would have been) and the battery itself, and a fan to cool the coolant. The charger will generate heat (a 3-5% loss) more or less depending on 120/240V.
These are things that always run when charging, and they take a bite out of the available power. The power that remains is what actually makes it to the battery.
When charging from 120V (9A=1080W or 12A=1440W), these fixed losses (assume 250W) take a bigger bite than when charging from 240V (16A=3840W).
The numbers have been changed to protect the innocent....

 

You're correct, of course. Since this thread started I've been researching trying to find exactly how much the 'overhead' actually is - The power drawn from the wall that doesn't go into the traction battery. When I saw the earlier comment about the savings using 240 volts was just 3%, I knew that wasn't even close to right so I was looking for the definitive number, in watts of the fixed losses

GM doesn't share that info evidently as I've been unable to source it, but there are some owners who closely monitor how many watts are drawn from the wall and how many Kw's that results going into the battery and they report that 240 volt charging is around 10 to 12% more efficient than 120 volt charging - I suspect if you only recharge using 120 volts at 8 amps, the number is even higher, as the associated pumps, low voltage charger and circuitry are running for even longer while you sloooowly fill the traction battery

Don

 

When I saw the earlier comment about the savings using 240 volts was just 3%, I knew that wasn't even close to right

It is actually correct - the average efficiency gain is only about 3%, on average. It only starts to get higher than that if you charge in very short cycles. Here is the science (not opinions):

https://www.veic.org/documents/defa...s/an-assessment-of-level-1-and-level-2-electric-vehicle-charging-efficiency.pdf

 

FI Spyder: I have to disagree - you seem to have not read the entire document thoroughly. The 15.8% energy efficiency gain is ONLY for low energy charge situations on public charging infrastructure (which they have found averages only 41 minutes of charge time and usually less than 2KWH of energy consumed).

The majority of Volt owners who are charging at home would be in the high energy charge situation where they are fully charging and using significantly more than 2kWH of energy. A 2kWH charge cycle would only be about 36 minutes of charging at Level 2 for the Volt, The "high energy" (> 2KWh) charge cycles experienced by Volt owners home charging stations would therefore average about 3% efficiency for Level 2 versus Level 1 charging.

 

laganon - Did you read the report you linked to?? I did - It's not my 'opinion' and your 'science' backs it up

Average efficiency of L1 charging when drawing less than 2Kw (that's us, as 120 @ 12 amps is only 1440 watts) is 70.7% and average efficiency when L2 charging drawing more than 2 Kw (again, that's us using either 240 @ 12 amps (2,880 watts) or 240 @ 16 amps (3,840 watts) is 86.5% - The difference is . . . . 15.8%

Those are averages - Your specific application will vary

Don

 

I read it the same way.
But, you are right, it does say kwh, and I read it too quickly as kw.

I am going to have to give this some more thought.
I could see that charging efficiencies would be lower in the case where battery temperatures had to be addressed for a small charge.
Then thermal management becomes a bigger percentage of the charge energy consumed, which by definition is a drop in efficiency.

 

My EV conversion runs 95% efficient, but I don't have cooling or heating controls during charging, I just shut down the charge if it is too hot or too cold.
This is a luxury the Volt doesn't have.

To do this right, you would really need to get data for an entire year on a Volt, and this is going to vary depending on where you live because ambient temperatures make a big difference in the results.

I have observed a wide range of additional electric loads running at various times during charging:

When charging I have seen the following:

• No cooling or heating (system quiet, max efficiency)
• Balance of plant computers baseload
• Water pump running (probably cooling the charger)
• Radiator fans running
• AC Compressor running (cooling batteries)
• Electric heaters running (heating the batteries)

If I were doing the battery thermal management today, I might not be so conservative with the cooling numbers for example during charging. This would have an impact on charging efficiency during hot periods.

 

Don M and FI Spyder: you both are confusing "power" with "energy". A kilowatt (kW) is a unit of power and a kWh is a unit of energy. Energy is power used over a specific period of time.

The document specifically is talking about energy, not power. Energy efficiency is calculated using a unit of energy, not power.

For a better understanding of that difference please read this: https://cleantechnica.com/2015/02/02/power-vs-energy-explanation/

The document is talking about energy efficiency, and hence my comments above still stand: for charge cycles where the vehicle is plugged in for periods where it consumes more the 2kWh of energy then the efficiency of Level2 over Level1 is only 3%. But if you do charge in cycles less than ~ 40 minutes (highly unlikely) then that efficiency increases to about 15%...

 

Here’s a thought experiment: The window sticker rates a Volt for ev miles on a full charge, and for MPGe (miles using the energy available in 33.7 kWh of wall power), which allows you to determine the amount of wall power pulled during the EPA testing to fully charge the battery for the vehicle being rated.

The Gen 2 Volt: 53 ev miles using (53/106 x 33.7) = 16.85 kWh from the wall.

Gen 2: ~14.2 kWh of usable power in a full charge = ~84.3% of the 16.85 kWh from the wall.
Or, the amount needed to recharge is ~118.7% of the kWh Used.

My 2012 Volt: 35 ev miles using (35/94 x 33.7) = 12.55 kWh from the wall.

Gen 1 Volts have a 65% usable soc window, so for a 2012 Volt: ~10.4 kWh usable power in a full charge = ~82.88% of the 12.55 kWh from the wall.
Or, the amount needed to recharge is 120.7% of the kWh Used.

These charging efficiencies of ~82.8-84.3% seem to be in the ballpark of the charging losses cited earlier in this thread when using L2 charging.

If L1 charging efficiency drops to ~71%, then the amount needed to recharge is ~140.8% of the kWh Used, or ~14.64 kWh for the 2012 Volt (an additional ~2.1 kWh of wall power) and ~20.0 kWh for the Gen 2 Volt (an additional ~3.15 kWh of wall power).

That’s an extra, what... $0.25-$0.35 per full charge @ ~$0.11/kWh?

 

If L1 charging efficiency drops to ~71%, ...,

You are missing the facts once again. It is true that Level2 charging efficiencies are about 83-85%. But Level1 efficiencies are only on average 3% less, NOT 71-72% versus 83%. Those lower Level1 efficiencies are ONLY in situations where you are charging for very short intervals (<= 2kWh).

Please reread the document linked above...

Consequently, if say it takes 16.5 kWh of energy to fully charge a Gen 2 Volt from a Level 2 charger (which is a typical number), then it would only take 3% more to do the same energy charge from a Level 1 charger, so about 17kWh used (16.5*1.03). Hence at 11c per kWh the saving per charge is only 5.5 cents.

That is why repeatedly on this forum it has been shown that buying and installing a Level 2 charger should not be done for electrical cost savings (you will never recoup that amount) but only for time to charge convenience....

 

Thanks lagagnon for laying out the data so well.

Not having access to 240 volt ac I did my tests using only 6,8,12 Amps at 120 Volts ac.

8 amps because I share the power plug at night with the condo car port lighting system.
6 amps to see if during a good wind my ham-station wind system would charge the Volt out on the farm. ( using a DIY- EVSE)

lets just say the ac line voltage difference between city and county changed the number more than the EVSE amps

 

It is a convenience/lifestyle decision. For me, since we do a number of top offs of 4kw or less, it may be slightly more efficient, but that was not a factor for us. Having the ability to leave home with a full charge midday after morning errands makes it worthwhile. Particularly in winter when running the heater. It allows us to maximize the Volt as an EV and minimize gas usage.




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It is a convenience/lifestyle decision. For me, since we do a number of top offs of 4kw or less, it may be slightly more efficient, but that was not a factor for us. Having the ability to leave home with a full charge midday after morning errands makes it worthwhile. Particularly in winter when running the heater. It allows us to maximize the Volt as an EV and minimize gas usage. Sent from my iPhone using Tapatalk

Electric cars are fuel efficient, and the cost of the electricity needed to provide 50-100 miles of ev range is relatively inexpensive in many areas. The advantages of electric propulsion are hampered, however, by the significant amounts of time it takes to refuel the car. This limitation is compounded by the limits to the size of the fuel tank that can be incorporated into the vehicle’s design.

In a sense, home L2 charging in a 120-volt world is more than a convenience/lifestyle decision. The significant reduction in charging time adds value to the operation for a price. I suspect most drivers fail to factor the cost of the L2 equipment and installation (and we don’t all have 240-volt outlets conveniently located near the parking areas) when calculating their "per mile" costs of home charging . I also suspect that most drivers also fail to include the costs associated with pre-conditioning the car when calculating their "per mile" costs of home charging.

The Vermont study of charging efficiencies at the L1 and L2 levels cited by lagagnon had a more long term goal in mind. As the number of electric vehicles increases, the impact they have on electric consumption similarly increases. An electric vehicle traveling X miles per year will require the use of Y kWh of wall power annually, and the actual quantity represented by Y is directly related to the efficiency of the vehicle’s recharging circuits. A vehicle with a high MPGe (distance traveled on a quantity of electricity measured at the wall plug) will provide less of a demand overall on the electric grid than a vehicle with a lower MPGe traveling the same miles (similar to a car getting 35 mpg will consume smaller annual quantities of gas than a vehicle getting only 20 mpg traveling the same distances). Note that even the small decrease in charging efficiency from using L1 charging equipment increases the amount of wall power required to recharge a battery, thus lowering the vehicle’s MPGe and increasing the demand on the power grid.

Improvement in vehicle charging efficiency would thus have an observable impact on the growth of the demand on the power grid arising from the use of electric cars.

Even the small differences observed in charging efficiencies at L1 and L2 levels have a long-term impact. Would upgrading public charging units from L1 to L2 level be a prudent long-term effort that should be taken by municipalities for reducing or limiting the increase in demand on the power grid?

 

marcusm: yes, pre-heating the vehicle is also an excellent reason for going Level2. Pre-heating on Level1 is almost useless. I did some tests myself on Level1 pre-heating and it took an additional 45-50minutes to recover a full charge after the 10 minute pre-heating cycle. You may as well just get in the cold vehicle, put the heater on full blast and go....

 

Yes. Since it has been blazing hot lately I forgot about this. Makes a big difference in the winter for Ev range. Again, helps keep it an EV to avoid gas.


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martik777: we have been discussing Level 2 versus Level 1 energy efficiencies, not whether there are costs savings of purchasing electrical energy versus gasoline. You are way off topic...

 

On going L2 was not a decision I had to make as the car came with a new L2 Charger. I just had to change the 240V outlet for the air compressor to a twist lock outlet to match the cord (and the one on the air compressor). Once you go EV you never go back. Once you go L2, you never go back. If I had to pay some of the outrageous prices some people have quoted, well that might well be another matter.