# charging efficiency

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#### rkshack

##### Active member
I am not sure the best way to ask this question. If I fully charge my leaf from 0 to 100% how much electricity does it take to do that. I know the battery holds 24kwh. How much of my house hold electricity does it take to fill that 24kwh. Is there some loss somewhere in the system that makes it use 25kwh of my electricity. I can't imagine that it is 100% efficicient. Also is there a difference in that efficiency with a home charging station and the trickle charger?

rkshack

From what I've read there is a flat 300w loss during charging. Using an L2 evse makes it charge faster so the 300w loss is for a shorter time, therefore the efficiency is better. I was using the included l1 evse but then had Phil at evseupgrade upgrade it to L2 rev 2 so I get the fastest L2 charging and the lowest cost L2. I highly recommend that approach, especially if like me, you can't score one of the free L2.

From what I've read there is a flat 300w loss during charging. Using an L2 evse makes it charge faster so the 300w loss is for a shorter time, therefore the efficiency is better. I was using the included l1 evse but then had Phil at evseupgrade upgrade it to L2 rev 2 so I get the fastest L2 charging and the lowest cost L2. I highly recommend that approach, especially if like me, you can't score one of the free L2.

Is the 300w for a full charge. So if I do a half charger from 12-24kw is the waste 150w. So if am doing my calculation for expense I should add .3 to the kwh that I am figuring. For example I pay \$.086 per kwh from my power company. So If I can calculate 24.3 x .086 to give me my cost in dollars.

rkshack

No it is 300w for the entire charging time. So, so say it takes you 12hours to charge using L1, with that you would be losing an extra 300w*12hours=3.6kwh. If you used an L2 for 5.25 hours instead, you would only lose 300w*5.25hours=1.575kwh. So you save a couple of kwh for about the same amount of battery charge.

Its 300w per hour

So it it takes 6 hours for a full charge then you used 300w x 6h or 1800 wh, or 1.8kWh.. since the average rate is \$0.12 per kWh then that works out to 22 cents

73% at 120 volts
84% at 240 volts
90%+ on DC

A lot has been made about the efficiency of the LV1 vs. LV2 charging . If you are making a decision based on cost savings between these two (that is, the recapture of the "wasted" kwh because of the longer recharge time of LV1) and not on the speed of the charging cycle (LV2 faster), you are wasting your time. :shock:

Using the provided example, you could recapture approximately 740 kwh/yr using the LV2 over the LV1. Even at my outrageous 14.4 cents per kwh, that's a yearly savings of about \$107. If I could install a LV2 charger for about \$1,200 (EVSE plus installation), the payback on that installation is 11 years :? . A lot more if the price of the EVSE LV2 charging station plus installation is greater than \$1,200. Not a very good investment.

The above, of course, is based on stable electricity costs (maybe) and the EVSE LV2 charger staying the same price (not likely). Conjigure with those two inputs and the payback period may be a bit shorter if the charger comes down in price and electricity rates rise significantly.

In my particular case (based on yearly estimated driving), the payback period is 25 years. So, unless you need the benefit of a fast charge vs. a slow charge, there is no need to use an LV2 IF what you are after is significant efficiency cost savings between the two systems.

I only use an LV1 and do just fine.

TonyWilliams said:
73% at 120 volts
84% at 240 volts
90%+ on DC

What are these percents?
rkshack

First off, you are not charging from zero to 24 kWh. Nissan has limited user access to only a percentage of the full pack capacity. Most of us accept the estimate that user available capacity is 21 to 21.5 kWh.

Owners who have charged at 240 Volts to "full" 100% charge from "turtle" (which is as empty as the car will allow you to get) in new cars with full battery capacity have reported using about 25 kWh from the power panel, as I recall. I think that I used 26.2 kWh, but my reading was considered an outlier.

rkshack said:
TonyWilliams said:
73% at 120 volts
84% at 240 volts
90%+ on DC
What are these percents?
rkshack
Those are the approximate efficiencies of charging the current LEAF at those voltages. As explained by others above, the 300 Watt "overhead" for charging is reduced with faster charging speeds.

I charge at 240 Volts, 16 Amps and get about 84-85% efficiency. This is calculated by comparing the power I use "at the wall" per mile with the power used per mile as reported by the car. In May my numbers were 4.36 miles/kWh at the wall and 5.1 miles/kWh in power use reported on the dash of the car.
4.36/5.1 = 85%
The missing 15% is the loss of the charging process.

Chieftan68 said:
A lot has been made about the efficiency of the LV1 vs. LV2 charging . If you are making a decision based on cost savings between these two (that is, the recapture of the "wasted" kwh because of the longer recharge time of LV1) and not on the speed of the charging cycle (LV2 faster), you are wasting your time. :shock:

Using the provided example, you could recapture approximately 740 kwh/yr using the LV2 over the LV1. Even at my outrageous 14.4 cents per kwh, that's a yearly savings of about \$107. If I could install a LV2 charger for about \$1,200 (EVSE plus installation), the payback on that installation is 11 years :? . A lot more if the price of the EVSE LV2 charging station plus installation is greater than \$1,200. Not a very good investment.

The above, of course, is based on stable electricity costs (maybe) and the EVSE LV2 charger staying the same price (not likely). Conjigure with those two inputs and the payback period may be a bit shorter if the charger comes down in price and electricity rates rise significantly.

In my particular case (based on yearly estimated driving), the payback period is 25 years. So, unless you need the benefit of a fast charge vs. a slow charge, there is no need to use an LV2 IF what you are after is significant efficiency cost savings between the two systems.

I only use an LV1 and do just fine.
For a low mileage driver—I am one such—the LEAF isn't a good "investment". Just saying....

For less expensive L2 charging one can use EVSEupgrade.com to covert the Nissan/Panasonic L1 cable to L2 for about \$300. If one's electrical panel is located in the garage, as many are, or there is already a 240 V circuit in the garage, adding an L6-20 240 Volt outlet is a DIY project that should cost less than \$50. (I put a meter on mine, so it cost me about \$100.)
My L6-20 outlet and meter

In addition to the convenience of being able to charge more quickly at home, those of us who live in the snowbelt also need to be able to preheat the car. That works a whole lot better on L2 than on L1. So, speed of charging and efficiency aren't the only considerations when going to L2.

Chieftan68 said:
A lot has been made about the efficiency of the LV1 vs. LV2 charging . If you are making a decision based on cost savings between these two (that is, the recapture of the "wasted" kwh because of the longer recharge time of LV1) and not on the speed of the charging cycle (LV2 faster), you are wasting your time. :shock:

Using the provided example, you could recapture approximately 740 kwh/yr using the LV2 over the LV1. Even at my outrageous 14.4 cents per kwh, that's a yearly savings of about \$107. If I could install a LV2 charger for about \$1,200 (EVSE plus installation), the payback on that installation is 11 years :? . A lot more if the price of the EVSE LV2 charging station plus installation is greater than \$1,200. Not a very good investment.

The above, of course, is based on stable electricity costs (maybe) and the EVSE LV2 charger staying the same price (not likely). Conjigure with those two inputs and the payback period may be a bit shorter if the charger comes down in price and electricity rates rise significantly.

In my particular case (based on yearly estimated driving), the payback period is 25 years. So, unless you need the benefit of a fast charge vs. a slow charge, there is no need to use an LV2 IF what you are after is significant efficiency cost savings between the two systems.

I only use an LV1 and do just fine.

Some PGE customers pay more than triple that and there is also the benefit of faster charging when both at home and when traveling. One does not need to install a level 2 charger if they have an upgraded unit. For some the difference in savings is much larger and an upgrade is under \$300. Even in SD this makes sense for many.

Both EVDRIVER and dgpcolorado have made my point. If you need the convenience of LV2, either because you need to quick charge at work/home because of the commute distance, or you take frequent trips on nights/weekends, or you need to preheat or precool the car, or you just like shoving 240 up instead of 120, than LV2 is not just a convenience but a necessity.

But for me, considering my commute and other driving habits, there is no need for an LV2 even if you consider an EVSE upgrade using the standard Leaf cable. Going the upgrade route instead of a charging station would still cost me around \$800 since I am not an electrician and I do not have a 220/240v outlet currently installed anywhere in my home (gas dryer, you see). So now payback is reduced from 11 years to a little over 7 (let's be generous--call it 5) in the previous example used. That may make sense given those parameters. But my personal payback is reduced from 25 years to 16.5 years--again, not very realistic.

Of course, one of the reasons a charging station is more desirable than the upgrade is the "pain-in-the-butt" factor of plugging the line in and out at home/work everytime you need to charge. Having the ability to just pull from the station and hook up seems to me a most time-saving benefit--and what is the monetary value of your time?

As for investment decisions surrounding the purchase of a Leaf considering the short commute that I have, that's an ethereous and elusive subject for most people, not just me. You have to factor in cost of electricity, miles driven, price of fuel, oil, maintenance, expected battery life, battery cell failure rates, battery cell replacement costs, comparable automobiles for payback period (and the media REALLY gets that wrong, often comparing the Leaf to the Versa--not hardly), ease of use (no more going to gas station), and on, and on. It's like the economy: not just a simple math problem with inputs and outputs.

I've factored those issues and others as best I can given the uncertain nature of all those factors and the uncertain nature of the future in general (as a wise man once said, "the future is not what we think it is.") My payback period for the purchase of the Leaf worked out to about five years, half of the average age of cars driven in the U.S. (10 years).

I'm satisfied with that.

Chieftan68 said:
Using the provided example, you could recapture approximately 740 kwh/yr using the LV2 over the LV1. Even at my outrageous 14.4 cents per kwh, that's a yearly savings of about \$107.
Since you live in California it is a bit surprising that you make that argument. A large percentage of Californians, excepting those with solar electric power, go over the electric power quota they have been assigned, and are penalized with very high rates for the excess. My quota is 11kWh/day, so an extra 2kWh wasted is a big thing. Your average may be 14.4 cents/kWh, but at least here, on the standard rate, if you use more than 14.3kWh/day (averaged over the month) you pay 30 cents/kWh for the excess (Well, OK, I exaggerate. It's really only 29.94 cents/kWh). You can't count those 2 wasted kWh as "average" usage. They are marginal use, and really can cost more than twice as much.

But that's only if I go more than 30% over quota, right? What's the chance of that happening? Well, to use adspguy's example, as you did, 5.25 hours at 240v means the car has pulled 20kWh, all by itself, and I would already be more than 80% over quota before I even plugged in my computer. :shock: And I'd better not turn on a light, because once I get to 100% over quota the price jumps again to 34 cents/kWh.

Ray

Granted that for some people L1 charging works fine. I just was pointing out that L2 doesn't have to be as expensive as you had stated and that it is necessary for some of us.
Chieftan68 said:
...Of course, one of the reasons a charging station is more desirable than the upgrade is the "pain-in-the-butt" factor of plugging the line in and out at home/work everytime you need to charge. Having the ability to just pull from the station and hook up seems to me a most time-saving benefit--and what is the monetary value of your time?...
This statement puzzles me. You point out that using an EVSEupgrade L2 involves lots of plugging/replugging and that this is a nuisance. Yet you plan to use L1 charging using the very same cable, involving plugging/replugging. Huh?

I would guess that a lot of people with just the Nissan/Panasonic EVSE leave it in their garage and don't bother with carrying it in the car. I've never needed my portable EVSE on the road since I got the car home, although I surely will later this summer when I venture much farther from home. However, in my remote rural location having the portable EVSE in my car is necessary for my peace-of-mind so I have two: one upgraded that lives in my garage most of the time, the other unmodified one stays in the car in case I guess wrong about a trip or the weather. (There aren't any L2 public charge stations here and calling Nissan for a tow to a dealer isn't practical since there aren't any within LEAF range.)

planet4ever said:
Chieftan68 said:
Using the provided example, you could recapture approximately 740 kwh/yr using the LV2 over the LV1. Even at my outrageous 14.4 cents per kwh, that's a yearly savings of about \$107.
Since you live in California it is a bit surprising that you make that argument. A large percentage of Californians, excepting those with solar electric power, go over the electric power quota they have been assigned, and are penalized with very high rates for the excess. My quota is 11kWh/day, so an extra 2kWh wasted is a big thing. Your average may be 14.4 cents/kWh, but at least here, on the standard rate, if you use more than 14.3kWh/day (averaged over the month) you pay 30 cents/kWh for the excess (Well, OK, I exaggerate. It's really only 29.94 cents/kWh). You can't count those 2 wasted kWh as "average" usage. They are marginal use, and really can cost more than twice as much.

But that's only if I go more than 30% over quota, right? What's the chance of that happening? Well, to use adspguy's example, as you did, 5.25 hours at 240v means the car has pulled 20kWh, all by itself, and I would already be more than 80% over quota before I even plugged in my computer. :shock: And I'd better not turn on a light, because once I get to 100% over quota the price jumps again to 34 cents/kWh.

Ray

Sorry about the pain you are feeling at the meter.

SDG&E indeed has a tiered system and it matches closely to yours. Fortunately for me, a single old man living alone in a small manufactured home, my baseline is, in relative terms, generous. I reach Tier 2 and Tier 3 only three months out of the year (July, August, Sept)--and that is from the AC. If I could live w/o that, I don't even think the Leaf would push it into those two additional tiers those months. So, in my case, its a matter of total usage for one person compared to the bill for a large household.

Last year's bill only pushed the price of the total kilowatt hours to a max 17 cents per (compared to the normal 14.4) for those three months. I went into the third tier for those three months. I understand what you are saying about marginal rates but you still have to count total kwh and divide that into your bill to get what you are paying per kwh--with or without the Leaf. So, in reality, I'm guesstimating my nominal rate will go up 2.6 cents per kwh--but for how many months out of the year is currently unknown.

I expect my electric bill to go up by 211 kwh per month via the Leaf. That's an average of seven additional per day. Of that, 25kwh/month are "wasted" compared to using a 240 hookup. That's \$4.25 per month (using the highest cost per kwh in last year's bill).

That's nothing to sneeze at--could buy an In-N-Out burger with that. However, even if I could manage a 240v EVSE upgrade for around \$500 including installation (not likely since as mentioned earlier I am not an electrician and do not have a 220/240v outlet), the payback for upgrading to Level 2 is still 10 years. Would you do it?

Chieftan, I just looked at your rate schedule, and if I am reading it correctly your SDG&E rates are much lower than our PG&E rates, so no more argument from me about payback time. (Your summer tier 3: \$0.173/kWh; our summer tier 3: \$0.2994/kWh.) I will say that I, too, am not an electrician, and did not have an available 240v outlet, but I put one in myself, including conduit, wires, sub-breaker box, breakers, and outlet, for about \$100. Um ... OK ... so I forgot to get a permit.

Ray

Ray, wish I had your smarts to do that sort of thing. I'm afraid I would electrocute myself. Never could do that kind of home project without hurting me or someone else and it ending up twice as expensive.

I'm hoping that a free standing charging system will dramatically fall in the next few years so I could at least consider that option in the future. But my driving habits would need to change dramatically as well.

For those where cost considerations as well as usage justify an LV2, it makes complete sense. I'm kind of jealous--would love to have the speed of the LV2 in case I was ever in an emergency situation.

But as my brother used to say, "You have to do the math" when doing cost/benefit analysis. That almost always puts a crimp into my "I want it now" syndrome. Such is life.

http://www.ehow.com/how_5163297_install-electrical-outlet.html" onclick="window.open(this.href);return false;

Chieftan68 said:
Ray, wish I had your smarts to do that sort of thing. I'm afraid I would electrocute myself. Never could do that kind of home project without hurting me or someone else and it ending up twice as expensive.

I'm hoping that a free standing charging system will dramatically fall in the next few years so I could at least consider that option in the future. But my driving habits would need to change dramatically as well.

For those where cost considerations as well as usage justify an LV2, it makes complete sense. I'm kind of jealous--would love to have the speed of the LV2 in case I was ever in an emergency situation.

But as my brother used to say, "You have to do the math" when doing cost/benefit analysis. That almost always puts a crimp into my "I want it now" syndrome. Such is life.

now i HAVE to think that someone has already mentioned Phil's EVSE Mod which allows you to convert the Nissan supplied 120 volt charging cable into 240 for a few hundred \$\$'s right? (now why Nissan does not already do this? i am guessing that might be a surprise for the 2013's???)

as far as getting the 240 hookup. you live in one of the largest plug in communities in the US . get on Facebook. sign up for the "Nissan Leaf owners of San Diego" or whatever they are called. there is a TON of knowledge and skill there and you might be able to talk someone into helping you get it done for the price of parts and a 6- pack.

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