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Discussion Starter · #1 ·
I had an electrician tell me that a 240v charger will use less electricity to charge my car and therefore cost me less to charge my car. I thought that it uses the same amount of electricity but just charges twice as fast (i.e. at twice the rate).

I'm not an engineer so I thought I'd ask here. It didn't sound correct. He was trying to explain that it will cost me a lot less in the long run to charge my car if I have a 240v charger vs my stock adapter that came w/ the car. Is that true? I am not on a "time of use" type plan btw, just a standard pay-for-the-amount-you-use plan.
 

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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
 

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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.
 

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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.
 

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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
 

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Discussion Starter · #8 ·
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.
 

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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...
 

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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
 

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Discussion Starter · #11 · (Edited)
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
 

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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
 

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Discussion Starter · #13 ·
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.
 

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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.
 

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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.

Cable Electronic device Technology Electronics accessory Electrical supply

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)
 

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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
 

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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.
 

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Discussion Starter · #18 ·
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
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.
 

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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.
I don't see it making a difference. It's only going to pull however much it's going to need regardless how big the breaker is (otherwise radios plugged into 15amp breakers would be blowing all the time). If it shorts out it's going to short out whether it's on a 20 amp breaker or a 30 amp breaker. The only thing with pigtails is in introduces another surface(s) to get corroded to build up resistance which builds up heat which increases resistance until you have a problem.
 

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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?
 
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