Only 18 KWh Usable Energy for MY Leaf--Retest Shows 20.3 KWh

[TickTock]

I decided to test the whole range. Drove it until it stopped (at 4 gids), then performed a 100% charge pulling a total of 22.6kWh from the wall (well 2.7 of that was from my generator but I had power meter on both so this is a measured total - not a computation). Interestingly, I picked up 5 gids! Before today I always only got 238 or 239 gids on a 100% charge but this time I got 244.

 

[Stoaty]

I decided to test the whole range. Drove it until it stopped (at 4 gids), then performed a 100% charge pulling a total of 22.6kWh from the wall

Assuming 87% charging efficiency, that would be 19.7 KWh usable--pretty low.

 

[TickTock]

I decided to test the whole range. Drove it until it stopped (at 4 gids), then performed a 100% charge pulling a total of 22.6kWh from the wall

Assuming 87% charging efficiency, that would be 19.7 KWh usable--pretty low.

Yeah, one more piece of evidence that my battery bites. I guess I may be finding out how good that warranty really is...

 

[TonyWilliams]

But, I fairly consistantly see smaller amount of energy per soc # above 200 (and below 100) than I see between 100 & 200.

I think an interesting next experiment is to get a Gids/mile average from the middle of the range, say 140 Gids, and then keep expanding out to see where the Gids/mile change, as your theory suggests (and that I suspect).

Another job for a dynamometer, or a track.

One more issue... obviously, we don't all get 281, or even close. But if we drive to turtle, you'll get really, really close to ZERO Gids.

So, there's really three parts of the battery Gid equation. The center half-ish, the bottom 1/4-ish, and the top 1/4-ish.

 

[Stoaty]

One more data point (drive from Claremont back to L.A.):

Charged to 80% (226 gids)
Drove 48 miles
Ending SOC - 136 gids
Efficiency from Center Console - 7.1 miles/KWh (it is, after all, a 900 foot elevation loss)

Total miles available = 48*273/(226-136) = 145.6 miles
Total KWh usable = 145.6/(7.1-0.1) = 20.8 KWh

 

[aqn]

It seems to me that 18 or 19 kWh could be the amount of usable energy after factoring in discharging losses. Assuming that 24 kWh is the "ultimate" capacity and that the "usable" capacity is closer to 20 or 21 kWh, a discharging efficiency in the ballpark of 85 - 95% could bring us down to 18 or 19 kWh actually available to the motor and accessories.

Although not tested by a complete discharge of the battery, my results suggest that--at least for my car--I should be multiplying the miles per KWh from the dash by 18.2 to get the total miles available on a full charge.

FWIW, my empirical data (gathered over 90 charge events so far) indicates each SoC bar equals 1.38 kWh, if one assumes that the mi/kWh figure is correct. Additionally, if we assume that there are 13.5 SoC bars altogether, the total available capacity is then 1.38 x 13.5 = 18.63 kWh. (A reserve of 1.35 SoC bars is my seat-of-pants guess based on number of miles between LB-VLB and VLB-turtle that I have seen on here.)

What I still can't square with is why 18-19 kWh? Can it be that 5-6 kWh of capacity is being withheld? If my empirical figure of 1.38 kWh/bar is accurate, 24 kWh capacity would equate to over 17 SoC bars!!! One or more of these might be true:

1. The LEAF's mi/kWh figure is wrong/manipulated.
2. The claimed 24 kWh capacity is wrong; the actual capacity is much less.
3. The battery actually is 24kWh but Nissan is intentional disallowing use of 5-6 kWh in interest of longevity.

I decided to test the whole range. Drove it until it stopped (at 4 gids), then performed a 100% charge pulling a total of 22.6kWh from the wall

Assuming 87% charging efficiency, that would be 19.7 KWh usable--pretty low.

Low, but it is in the same ballpark as numbers arrived via other methods, e.g. my method, so while we don't know whether it's accurate, there is a strong case that it is consistent.

Yeah, one more piece of evidence that my battery bites. I guess I may be finding out how good that warranty really is...

I don't know if it's necessarily true that your battery "bites". Some/many people are seeing battery capacity in the 18-19 kWh.

 

[Stoaty]

Although not tested by a complete discharge of the battery, my results suggest that--at least for my car--I should be multiplying the miles per KWh from the dash by 18.2 to get the total miles available on a full charge.

FWIW, my empirical data (gathered over 90 charge events so far) indicates each SoC bar equals 1.38 kWh, if one assumes that the mi/kWh figure is correct. Additionally, if we assume that there are 13.5 SoC bars altogether, the total available capacity is then 1.38 x 13.5 = 18.63 kWh.

Yes, but did you notice that I believe my first test was not valid, and that two subsequent tests came up with a figures of 20.3 and 20.8 for the usable KWh in the battery pack? Of course, this is using the miles/KWh figure rather than the total amount of energy put into the battery to recharge it. The latter is not easy to know even if the KWh from the wall is known, since we don't know the efficiency of L2 charging for sure.

 

[edatoakrun]

Although not tested by a complete discharge of the battery, my results suggest that--at least for my car--I should be multiplying the miles per KWh from the dash by 18.2 to get the total miles available on a full charge.

FWIW, my empirical data (gathered over 90 charge events so far) indicates each SoC bar equals 1.38 kWh, if one assumes that the mi/kWh figure is correct. Additionally, if we assume that there are 13.5 SoC bars altogether, the total available capacity is then 1.38 x 13.5 = 18.63 kWh.

Yes, but did you notice that I believe my first test was not valid, and that two subsequent tests came up with a figures of 20.3 and 20.8 for the usable KWh in the battery pack? Of course, this is using the miles/KWh figure rather than the total amount of energy put into the battery to recharge it. The latter is not easy to know even if the KWh from the wall is known, since we don't know the efficiency of L2 charging for sure.

Got CW update?

As I posted earlier, Since I had the Carwings update done on 8/3, my Dash and Carwings miles/kWh numbers seem to match.

Even more interestingly, the daily Driving Records/electricity consumption now seem to accurately reflect the kWh delivered from my Modified L2, as best as I can calculate by recharge time.

Has anyone tried a 100% charge to Turtle discharge drive since having the update?

What total electricity consumption (kWh) did carwings report-and do you believe it to accurately reflect total battery capacity?

If you have a meter at the wall, what L2 charging efficiency percentage did it show for your recharge, using the Carwings energy consumption report?

http://www.mynissanleaf.com/viewtopic.php?f=31&t=5423

 

[DaveEV]

I decided to test the whole range. Drove it until it stopped (at 4 gids), then performed a 100% charge pulling a total of 22.6kWh from the wall (well 2.7 of that was from my generator but I had power meter on both so this is a measured total - not a computation). Interestingly, I picked up 5 gids! Before today I always only got 238 or 239 gids on a 100% charge but this time I got 244.

Interesting - I suspect that for whatever reason your battery is more out of balance than usual - a few more "full" cycles with sufficient time for balancing might bring your 100% gid count up more.

I might try getting down to 2 bars or so and charging to 100% a couple more times to see what happens. Depending on your commute that may not be that easy.

BTW - I assume that the 2.7 kWh from your generator was how you got the car home after draining it?

 

[TickTock]

I decided to test the whole range. Drove it until it stopped (at 4 gids), then performed a 100% charge pulling a total of 22.6kWh from the wall (well 2.7 of that was from my generator but I had power meter on both so this is a measured total - not a computation). Interestingly, I picked up 5 gids! Before today I always only got 238 or 239 gids on a 100% charge but this time I got 244.

Interesting - I suspect that for whatever reason your battery is more out of balance than usual - a few more "full" cycles with sufficient time for balancing might bring your 100% gid count up more.

I might try getting down to 2 bars or so and charging to 100% a couple more times to see what happens. Depending on your commute that may not be that easy.

BTW - I assume that the 2.7 kWh from your generator was how you got the car home after draining it?

Yup. Had to bring it all the way to 25 gids before it let me put it back into drive to bring it home.

Looks like 244 is here to stay. At least my next charge also reached it. I am reticent to try again, though, until we really know what a gid is. Wishful thinking, but it is possible lower max gid levels are actually *good* and I am observing the degradation of my battery. Even at 239 gids, I wasn't that far from Stoaty's number. Maybe the sw increases the target gid count in an attempt to keep constant capacity. As I said, wishful thinking, but I will wait for more information before trying again.

 

[davewill]

...Looks like 244 is here to stay. At least my next charge also reached it. I am reticent to try again, though, until we really know what a gid is. Wishful thinking, but it is possible lower max gid levels are actually *good* and I am observing the degradation of my battery. Even at 239 gids, I wasn't that far from Stoaty's number. Maybe the sw increases the target gid count in an attempt to keep constant capacity. As I said, wishful thinking, but I will wait for more information before trying again.

Seems more likely to me that the gids at the top of the scale just don't mean very much. I'd be interested to see how far the 281 people are able to get before THEY reach the 240 neighborhood you're in. I bet it won't turn out to be very far, and that all of these numbers represent a reasonable variation. Rendering gids as a linear percentage was always a questionable practice.

 

[mark13]

Averaging 5.8 KW/M is very good on the main dash..That is what Im averaging currently..That should be getting you 120+ miles per charge tho..

 

[DaveinOlyWA]

Consumer Reports has "verified" with high level measuring equipment of an unspecified nature of the 85% charging efficiency and that is wheel from well efficiency. what part gets to the battery would be implied to the 100% of the 85% if that makes sense to anyone. this is assuming (not a easy one) that the Car is reporting its efficiencies accurately in relation to how far it has traveled in computing its own miles/kw figure.

in any measurement that deals with electricity, charge, etc. unless we are counting electrons, its all really an estimate. the only real way to doing it is to track records over time

using single trip stats is not going to work. take 20 trips, toss out the highest and lowest and average the rest if you must, but that is really the only thing i would bank on.

then we need to add in possible errors from each measurement including the big unknown; the Car. i am assuming it to be accurate since i do not have access to an accurate version of Carwings (is there such a thing??)

the other thing is the battery pack itself. all battery packs are not created equally and i fully expected user reports to vary widely. but is it the pack, the measuring tools used or simply the huge variance in driving conditions?


if we all used the same charging/monitoring system, that would make me feel a lot better about everything. but we are not. and i cannot say i have a lot of trust in some of the systems you are using.

as for me; i have an analog meter that tells me how much i am getting from the wall that is reputed to be 99.9+% accurate, so that is a given. the rest i have to use is what you all have. the Car.

now; using the 12 amp 240 mod from Phil i am running a rock steady 83.3% efficiency. Consumers Reports states the EVSE (not specified which one, but i think its CT?) is 85%. using the unmodified 120 volt EVSE will give you 75% which i also verified for the 6 months i used 120 volt exclusively monitoring power from the wall with a Kill a Watt which is also supposed to have a high degree of accuracy.

so, now we go back to the car; some here have reported measurable discrepancies with the odometer. i have not. keep in mind, i have been meticulously tracking my driving which includes distances, etc for 8 years including distances correlated with VZ Navigator, Google Maps and an EV that had a range of 20 miles (had to plan to make sure i could either get back home or get to a plug!!)

so distances i have traveled i have down pat (carried a book in my Zenn that plotted distances from destinations to destinations including several measured distances from intersections to intersections on my commonly traveled routes) and all those distances pretty much match the odometer in the Leaf. so no real errror there at least in my case.

the other point to investigate; the weather. i have become to realize that ambient temps WITHOUT CLIMATE CONTROLS (hope you caught that point) will affect efficiencies by at least 10-15% when getting colder (15-20º F)

so if cold is that affective, heat must play a part as well. its been reported that "100%" seems to be a wandering target for many and i believe its thermal charge management doing its job. what i have not seen (have been busy so have missed a lot of topics here) is a correlation between the measurements of SOC verses the temperatures seen.

 

[TonyWilliams]

the other point to investigate; the weather. i have become to realize that ambient temps WITHOUT CLIMATE CONTROLS (hope you caught that point) will affect efficiencies by at least 10-15% when getting colder (15-20º F)

so if cold is that affective, heat must play a part as well.....

Certainly, I don't know how much ambient heat affects charging, but it definitely affects range above 70F.

Nissan engineers in the Phoenix area doing heat testing report 10-20% range reduction. Which corresponds somewhat to my rule-of thumb of:

Temperature Increase: Subtract 1% from range for each 4F/2C above 70F/20C

So, at 118F ambient temperature, the math is (118-70=48/4=12), or 12% reduction in range. It's probably a bit higher than that, perhaps 3F per 1%.

 

[TickTock]

Nissan engineers in the Phoenix area doing heat testing report 10-20% range reduction.

do you have a reference? I would love to read that report.

 

[SanDust]

What I still can't square with is why 18-19 kWh? Can it be that 5-6 kWh of capacity is being withheld? If my empirical figure of 1.38 kWh/bar is accurate, 24 kWh capacity would equate to over 17 SoC bars!!! One or more of these might be true:

3. The battery actually is 24kWh but Nissan is intentional disallowing use of 5-6 kWh in interest of longevity.

You can't fully charge and discharge a Li-ion battery and have it continue to function. Ditto for storing it at high or low temperatures fully charged.

The EPA announced last November that the Leaf used 21 kWh of the 24 kWh available, leaving 3 kWh at the top and bottom. That's quite aggressive. If you're short a couple of kWh that is probably due to Nissan keeping something in reserve after the initial spate of people running out of juice and the difference in not counting battery usage not capable of fully powering the car.

The big question which some of this measurement will eventually answer is: How long will the AESC cells last? We know that they're not designed like the LG Chem cells to last 300K miles but we don't know just how short of that benchmark they'll be.

 

[LEAFfan]

Certainly, I don't know how much ambient heat affects charging, but it definitely affects range above 70F.

Sorry Tony, but I'm going to have to shoot some holes through that theory. All through the summer, in all of our heat, my m/kW h didn't vary much. The only reduction I saw was when my wife needed the A/C. Otherwise, there was NO reduction in my range nor continues to be in our cooler temps we are having right now. When Nissan did that summer heat testing, I'm sure they weren't hypermiling it so maybe driving it 'hard' will reduce the range more in the heat.

 

[SanDust]

So, at 118F ambient temperature, the math is (118-70=48/4=12), or 12% reduction in range. It's probably a bit higher than that, perhaps 3F per 1%.

Why would this be? Drag would be less as would rolling resistance and drive train losses. Battery performance would be enhanced. If the AC was on that would definitely reduce the range but since the Leaf doesn't have a TMS I don't see any additional electrical loads if climate control is off.

 

[DaveinOlyWA]

Nissan engineers in the Phoenix area doing heat testing report 10-20% range reduction.

do you have a reference? I would love to read that report.

not for heat and this is a bit unrelated to charge capacity but the colder weather has reduced my efficiency by 15%.

http://www.mynissanleaf.com/blog.php?u=291&b=107" onclick="window.open(this.href);return false;

my driving habits, routes, speeds, etc have not changed. driving conditions do create a variance of 4-7% but i am continuing to see 4.8 to 5 miles/Kw and have still not used any climate controls. i did get that portable heater for defrost purposes from Harbor Freight and am still evaluating its effects on my range after 2 days of use.

prelim reports; well, its electric so it does have some effect but on energy consumption screen, the needle does not move when its on or off. unlike heat; 3 Kw, Defrost 4.5 kw or rear defrost; 250 watts, the 12 volt heater does not move any needles.

its listed at 12 VDC and 13 amps. states should not be run more than 20 minutes at a time so we will see. the power cord does get slightly warm after a while. longest run time was this morning (breakfast with Son thru FF drive thru) about 20 minutes or so, maybe 25. but at $8.99 even if it burns up, its worth seeing if this is a good solution for defrost and a bit of warmth

its on a slide mount and this morning i used it to put it on my lap for a few minutes and it does provide a bit of warmth without being hot enough to burn me.

**edit** LOL!! got so sidetracked i forgot to respond to the post....

ya, anyway, heat can be a limiting factor on range in that the warmer the pack, the lower "100%" has to be to protect longevity. iow, hot weather like 90º may see only 95% pack capacity restrictions to prevent overcharging when compared to a temperature adjusted capacity to a standard conditions like ummm STP or 68º.

 

[Stoaty]

The EPA announced last November that the Leaf used 21 kWh of the 24 kWh available, leaving 3 kWh at the top and bottom.

Do you have a reference for this? I haven't ever heard of this info coming from the EPA.

As far as temperature effect on range, my observation is that range was better through the summer (90-95 degrees at work, battery in the 6 bar temp range about 40% of the time), and isn't as good now that temperatures have cooled off. Of course, it may not be temperature that is causing the change, but that is the only correlation I can see.