Cost and time of 220v vs 110?

What I cant understand about the 220v charging vs 110.

First, I was assuming that - even though 220v is faster, that my electric bill will be about the same, since electricity is charged by watts (amps*volts?).

However, it does not seem to me that it takes 2x as long to charge with the 110, it seems to charge 3x as long.

So... does it really cost the same, and its just longer to charge with 110? Or is is cheaper to charge with 220?

What you are missing is differences in charging efficiency. There is a fixed draw while charging, for cooling pumps and such, which end up drawing power for a longer time on 120V. In addition, the charger itself may be a bit more efficient at 240V as it don't have to boost the voltage as much.

the biggest thing you are missing is that 120 volts only charges at 12 amps. so power in is 120*12 or 1440 watts. 240 charges at 16 amps or 3840 watts which is the reason why 240 charges more than twice as fast.

the other thing already mentioned does not seem to change from 120 to 240 is the cooling system which draws a constant amount of power that is nearly the same.

but generally charge at 240 and you will get 88-90% of the power from the wall to the battery so you are juicing up at about 3840*90% or 3456 watts per hour. with 120 its about 76 % or 1440*.76 or 1094 watts. so divide one by the other and you have your 3 to 1 ratio

tkutter said:

So... does it really cost the same, and its just longer to charge with 110? Or is is cheaper to charge with 220?

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It matters a lot if you are on the Time of Use electric plan.
For example, SCE Super-Offpeak rate is only good from 12am - 6am, so you only have 6 hours to charge at lowest rate.
With the 120V EVSE, you can only charge about 25 miles per day, so it may pushed you out to the more expensive Offpeak rate instead.
With the 240V EVSE, you can charge about 75 miles per day, so you'll always have 80% charged everyday before you drive

But the 240V is really more about convenience. Buy + Install should be around $1000 for most people.
You'll be unlikely to save enough on electricity to justify the spending based on pure cost perspective.
For me, I actually spend more than $2500 for the installation because I decided to put up a second panel for EV charging rate.
So while I don't have to worry what time I'm using my electricity, I can also installed the second EVSE easily in the future for new car.

DoxyLover and DaveinOlyWA have pretty well covered it, though I think Dave's numbers are a little high for 240v charging. My (somewhat conservative) rule of thumb is that you actually get about 1kW into the battery at 120v 12A, and 3kW at 240v 16A. This fits nicely with what Nissan has said: 1kW "trickle" times 21 hours = 21kWh. 3kW "normal" times 7 hours = 21kWh. We know that the usable capacity of a new battery is about 21kWh. Reality is more complicated than that, because the charge rate tapers as you approach 100%, and the Nissan 7 and 21 hour numbers are from Low Battery Warning, not an empty battery. But those two factors somewhat balance each other out.

DaveinOlyWA said:

the other thing already mentioned does not seem to change from 120 to 240 is the cooling system which draws a constant amount of power that is nearly the same.

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I'm not sure whether he was agreeing or disagreeing with DoxyLover here, but it is indeed a constant amount of power, which is a constant amount of energy per hour, and that does explain the differences in observed efficiency. I believe the cooling system pulls 200-250 watts. (This includes two pumps, two cooling fans, and the DC/DC converter.) Let's assume you put 15kWh in the battery. By my rule of thumb, that will take 5 hours at 240v 16A and 15 hours at 120v 12A. Here is how I see it breaking out, assuming 225 watts cooling and an average of 1 less than the maximum amps:
Ray

p.s. You may notice we are saying 120v and 240v, not 110/220. Though the lower numbers are commonly used in conversation in the US, the standard was raised to 120/240 more than 50 years ago.

Ahh, got it. Very good answers. Glad I found this forum!

At a minimum, consider getting your factory EVSE upgraded at http://www.evseupgrade.com" onclick="window.open(this.href);return false; so you can get both 240 volt and 16 amp charging, saving time and money.

I would go with the NREL Teardown data:

http://www.mynissanleaf.com/viewtopic.php?f=8&t=10307" onclick="window.open(this.href);return false;

Charger and EVSE efficiency (presumably L2) - 86.69%

i think i remember Phil saying cooling overhead was like 325 to 355 watts or so and the difference between the charging rates as to the overhead was negligible

DaveinOlyWA said:

i think i remember Phil saying cooling overhead was like 325 to 355 watts or so and the difference between the charging rates as to the overhead was negligible

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I don't follow... 325-355 watts compared to 1440 or 3890 total charge power is definitely NOT negligible... for 120v@12A it's 350/1440 or 25% loss (!!!) and for 240v@16A it's 350/3840 where 350W is still almost 10% loss...

maybe I misunderstood the comment?

ljwobker said:

DaveinOlyWA said:

i think i remember Phil saying cooling overhead was like 325 to 355 watts or so and the difference between the charging rates as to the overhead was negligible

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I don't follow... 325-355 watts compared to 1440 or 3890 total charge power is definitely NOT negligible... for 120v@12A it's 350/1440 or 25% loss (!!!) and for 240v@16A it's 350/3840 where 350W is still almost 10% loss...

maybe I misunderstood the comment?

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ya, my bad.
ya the 325-355 watts is a guess. dont remember the exact amount but the real number is the same so its either or or something in between.

the difference in the overhead between 120 volt charging and 240 volt charging is negligible. its like 10 watts or something relatively small.

as far as being negligible overall, most definitely not

Here are my charging measurements on the Leaf:

Charging using the original 120v EVSE: (112.5v recorded at EVSE input)

Standby Power: 4.9w
Charge Power in: 1.451kW
Power to Leaf Battery: 1.125kW
Total Power Lost: 326w
Total Charge Efficiency: 77.5%

These measurements are all using our Rev2 Upgraded EVSE:

120v: (112.6v recorded at EVSE input)
Standby Power: 1.7w
Charge Power in: 1.436kW
Power to Leaf Battery: 1.125kW
Total Power Lost: 311w
Total Charge Efficiency: 78.3%

240v: (239.8v recorded at EVSE input)
Standby Power: 3.4w
Charge Power in: 3.756kW
Power to Leaf Battery: 3.414kW
Total Power Lost: 342w
Total Charge Efficiency: 90.9%

All these measurements were with the Leaf pack at around 62 degrees F and ~65% SoC. Readings were allowed to stabilize before recording. The power to the Leaf battery was calculated by recording amperage at the cell interconnect level using a high-accuracy kelvin-connected current shunt, so the losses are a sum of all EVSE/Charger/Leaf systems. Charger input power was similarly recorded using lab-grade calibrated true RMS equipment, not a Kill-A-Watt.

These efficiency calculations do not take into account the coulombic loss in the Leaf's battery, and other Leaf systems during discharge, so this is only charging efficiency up to the battery pack itself but not including the pack, of which also has notable loss.

While I'm at it, someone asked me recently what the idle draw of the Leaf is. It bounces around a lot, but it's as low as 140w, typically around 160w with all accessories, lights, and CC off, and 230 watts for headlights and 360w with High-Beams on. (My Leaf will be slightly lower, as I've changed most of the incandescent bulbs to LED.) Again, these power measurements were derived by recording amperage at the cell interconnect level using a high-accuracy kelvin-connected current shunt.

If anyone wants to know any highly accurate information about the Leaf's systems, I might have already recorded it, feel free to ask!

-Phil

Ok, this thread made me question whether I was right about sticking with L1 only. So here are my numbers:

Assume 10,000 mi/yr (even though I only did 7000 last year).
Driving Style: 4 mi/KWH (I get 5 in the Spring to Fall, but 3.5 in the winter).
Electricity: $0.06/KWH no TOU because of all those dams.

10,000 mi/yr x KWH/4 mi x 1/0.75 (L1 efficiency) x $0.06/KWH = $200/yr
10,000 mi/yr x KWH/4 mi x 1/0.85 (L2 efficiency) x $0.06/KWH = $176/yr

So, L1 will cost me $24/yr more than L2. Even using Phil's $300 upgrade (and ignoring the fact that I don't have 240 VAC in the garage), it would take 12.5 yr to breakeven. Using the more realistic 7500 mi/yr reduces the difference to $18 and 17 yr to breakeven. One day I may get 240 V into the garage (it's over 100 ft to the panel in the basement and through two concrete walls), but doing it will make Phil's upgrade look like peanuts. I think I'll wait until there's a real need (like maybe I become a traveling salesman or taxi driver).

Reddy

ok 31 watts more than i had remembered but still not much.

Ready; with your undoubtedly low power rates, you will never recoup the cost of any kind of L2 upgrade even if you went with Phils which is only a few hundred. now the reason i did it is because at 120 volts, i do not effectively have full range of the car. if i drive to an SOC of like 20% or less, I do not have enough time to recharge to 100% for the next day.

The Centrailia commute of 64 miles RT could not be done two days in a row. the LEAF simply could not recharge quick enough

duplicate

Reddy said:

Ok, this thread made me question whether I was right about sticking with L1 only. So here are my numbers:

Assume 10,000 mi/yr (even though I only did 7000 last year).
Driving Style: 4 mi/KWH (I get 5 in the Spring to Fall, but 3.5 in the winter).
Electricity: $0.06/KWH no TOU because of all those dams.

10,000 mi/yr x KWH/4 mi x 1/0.75 (L1 efficiency) x $0.06/KWH = $200/yr
10,000 mi/yr x KWH/4 mi x 1/0.85 (L2 efficiency) x $0.06/KWH = $176/yr

So, L1 will cost me $24/yr more than L2. Even using Phil's $300 upgrade (and ignoring the fact that I don't have 240 VAC in the garage), it would take 12.5 yr to breakeven. Using the more realistic 7500 mi/yr reduces the difference to $18 and 17 yr to breakeven. One day I may get 240 V into the garage (it's over 100 ft to the panel in the basement and through two concrete walls), but doing it will make Phil's upgrade look like peanuts. I think I'll wait until there's a real need (like maybe I become a traveling salesman or taxi driver).

Reddy

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The argument is usually not the cost, but the utility. If you don't have a loss of utility, then you are fine, but if there are situations where you simply lose range because you cannot get recharged in time, then it may be worth the hassle.

It does sound like adding 240v to your charging area would be difficult, but maybe not. What service is in your garage now? What wire feeds it, and how many conductors? If there are 2 circuits (would require 2 hots, a neutral and a ground), then you might be able to do it w/o running any new wire. If there is only one circuit, then you will not be able to do it unless you convert your existing circuit to 240v, thus leaving you with no standard 120v service in the garage.

If all you need in the garage is some minor lighting loads, etc, then maybe you could consider changing the existing circuit to 240v, then either installing 240v lighting, or adding a transformer. In extreme cases, sometimes this makes a lot of sense!

-Phil

Phil, thanks for the suggestions. Yes, there are two circuits but I haven't checked if they are on different legs. Since I use an electric lawn mower, weed eater and chipper, I use both circuits pretty much all summer. I will consider garage modifications for the future, but no limitation on Leaf use for me now. Work is 8 mi RT, shopping is 15 mi RT, maybe 40 mi RT to the other side of the "metroplex" (plus I located a L2 over there). Heck, I don't even pack the L1 with me in the car except for five or six trips out of town that were successful. My "need" outside of this is so remote that I have to find an excuse (http://www.mynissanleaf.com/viewtopic.php?f=51&t=9946&p=226115#p226115) just to try something new. Now, I did consider your EVSE upgrade for such out of town travel and it would be mandatory for a trip from here to Portland, OR which starts out with about 60 mi of complete desolation until reaching Crow Butte State Park. From there, it's another 78 mi of desolation to The Dalles, OR.

Reddy

Just FYI: If your two circuits are on opposite legs (they should be), then you could easily use a Quick220 type device with our Rev1 upgrade and be charging at over twice as fast. This would require no wiring changes in your garage.

If the 2 circuits are separate runs of romex, (possible) and 12AWG, you could even convert one to 240V and install an L6-20.

Seems like your setup is adequate, my only advice would be to replace the outlet you are using presently with a heavy-duty spec-grade one. Most of the stuff you'll find installed by contractors are low-end. This will ensure you don't have any additional voltage drop, and make it safer.

It's also a good idea to secure the EVSE "brick" in such a way so it isn't hanging by it's cord.

-Phil

Again, thanks. I replaced the outlet a couple of months ago and have had the brick attached with a nail or held up on a shelf since Day 1 (thanks to reading all the great info provided at this site). Since I mostly only charge a couple of hours per night, I've yet to see any heat buildup.

I am currently considering this as well. We are looking/hoping to get our Leaf in the next month or so, and we are currently in a rental house. We will be leasing the Leaf.

Our garage has both types of plugs -- regular 110 as well as a "large" plug that our dryer plugs into. We do not want to pay for any electricians fees or permanent upgrades to the house / garage itself as it is a rental, so we are considering going either trickle charge all the way or ESVE upgrade, which would be mobile.

A few questions:

1) Does the larger dryer plug mean we have 220V? Or would we have to confirm this in some way by hiring an electrician?

2) Is there a circumstance in which we would not be able to charge the Leaf using either 110v or 220v? E.g. our house is too old and it knocks out the power? Or would 110 always work, and 220 would be an issue? Again, we do not own the home so don't have a lot of history on the state of the electrical system.

3) I have a daily commute of 30 mi roundtrip (San Mateo / Mountain View, CA) with chargers available at work for a relatively pricey fee ($1/hr). We occasionally go up to the city (SF) on the weekends for a 40-50mi round trip. Should we consider 220 charging at home to be a deal breaker for us? We also have the option of our 2nd car & the train but if we get the Leaf I think we'd like to be able to use it

Appreciate any thoughts folks have! Apologize in advance if these have been asked elsewhere -- I'm pretty new