Leaf Miles / KWh is Wrong Or Usable bat. cap. is not 24 KWh

Herm said:

DaveinOlyWA said:

hate to burst your bubble, but many of us have found the 120 volt efficiency to be around 75% so you would have around 19.5 KWH used.
... i am looking at a charging efficiency of probably 88-90% then a set overhead for the charge management (which should be small) and cooling system which is small but still significant.
so the longer the charge time, the greater the hit on the overall charging efficiency. most have seen 85-88% on 240, around 75% on 120.

Click to expand...

I'm ok with the efficiency numbers for typical power supplies and chargers, but the 350w fixed overhead sounds a bit too high.. but in any case is all a case of circular logic since NO ONE has measured the wattage going in and out of the battery while being charged.. who will be the first dedicated Lead owner to actually make some measurements?

Click to expand...

Phil (the EVSE mod guy) will be making some measurements to better nail down the real efficiency of the 240 volt EVSE and also trying to figure out how much power the cooling system is taking.

remember the 350 watt # is also charger inefficiencies, so if looking at cooling alone, its probably in the 175-200 watt range

JessEV said:

After 8.5 hours of charging on L1, I have recovered 7 bars. At 1.33kWh * 8.5 I got 11.3kWh from the wall.

Click to expand...

You can't assume 1.33 kWh either - you should measure using a kill-a-watt to get true energy going in at the wall.

Look at this sticky ... this gives the range of each bar. Top bar was 4% and rest 8%. But this is before the firmware upgrade. It would have changed to become more nonlinear now.

http://www.mynissanleaf.com/viewtopic.php?f=31&t=2390

Herm said:

I'm ok with the efficiency numbers for typical power supplies and chargers, but the 350w fixed overhead sounds a bit too high.. but in any case is all a case of circular logic since NO ONE has measured the wattage going in and out of the battery while being charged.. who will be the first dedicated Lead owner to actually make some measurements?

Click to expand...

I don't think it will be 350w fixed. At least the cooler will depend on temperature, I'd think - unless they don't measure that and the coolant circulates irrespective of the temperature.

My experience is that the change efficiency (or rather the ratio between mpkwh at the wall and at the dash) vary on a daily basis. I don't know whether it is because the charger efficiency varies or because the mpkwh at the dash is not accurate.

Between Dave's and evnow's posts, I'd say I'm right in the range--wall to wheels about 3.7 mi/kWh. Very non-scientific in that I'm just adding up what my SmartMeter says for the 5 hours I charge (minus the house baseline from midnight-5AM) and dividing that into my mileage for the previous day. Probably good to 5%.

I like the term "Wall to Wheels" as it's very descriptive. I've been calling it "Consumed". Is there a standard term in the EV community?

gascant said:

I like the term "Wall to Wheels" as it's very descriptive. I've been calling it "Consumed". Is there a standard term in the EV community?

Click to expand...

Well to Wheels is the standard way to measure CO2 emissions for a gas car. It has now been adopted for EVs. You can see this terminalogy in EPA funded research.

evnow said:

gascant said:

I like the term "Wall to Wheels" as it's very descriptive. I've been calling it "Consumed". Is there a standard term in the EV community?

Click to expand...

Well to Wheels is the standard way to measure CO2 emissions for a gas car. It has now been adopted for EVs. You can see this terminalogy in EPA funded research.

Click to expand...

Thanks evnow. "Wall to Wheels" it is, then.
The nice thing about the SmartMeter (which I forgot to add, above) is that it gives you the actual cost of the electricity consumed. So, in the first half of my billing cycle, I've found that it's costing me $1.90/day to commute 61 miles RT. At $9.50/week it beats the Prius's $24 pretty handily.

DaveinOlyWA said:

Phil (the EVSE mod guy) will be making some measurements to better nail down the real efficiency of the 240 volt EVSE and also trying to figure out how much power the cooling system is taking.

remember the 350 watt # is also charger inefficiencies, so if looking at cooling alone, its probably in the 175-200 watt range

Click to expand...

I would consider the overhead any extra power that does not go into the battery, that would include charger losses, charger cooling losses, EVSE loses and EVSE cooling losses.. plus whatever other load is running on the car at the time (not including AC) necessary to run the charger, probably carwings communications, BMS plus assorted computers and sensors. Yeah, perhaps it does add up.

evnow said:

Well to Wheels is the standard way to measure CO2 emissions for a gas car. It has now been adopted for EVs. You can see this terminalogy in EPA funded research.

Click to expand...

Some people could care less about CO2.. in any case power at my outlets is CHEAP, only $0.11 a KWh, all I care about is range or "battery-to-wheels" efficiency.. if we had an on-board genset like the Volt then we would worry about MPG including the efficiency of the genset in the chain.. but I really could care less about the local utilities power plant/transmission line efficiency, even EVSE charger cords losses are almost meaningless. Again, power at the outlet is cheap and plentiful.. plus its American made .. in most places.

I care about two things:

1) Cost per mile, which becomes Miles per kWh as a normalized measure. (I prefer Watts per Mile)

2) Useable Range, and predicted range while driving, because it impacts planning and useability

To that, end I'm keeping detailed track of the total energy consumed by the LEAF. This is represented completely and accurately by the SDG&E utility meter. It's what I pay. I don't care if the EVSE is lossy, the charger is inefficient, or the energy goes to waste-heat during charging -- I have to pay for it, and I don't have any control over it. To some extent, I don't even care if the meter is inaccurate. It is what it is.

So, if I begin my day at 100%, drive my commute and errands, and charge up at midnight, that's a really good and irrefutable measure of cost. Not a lot of wiggle room or estimated factors.

Right now I'm running about 2.5 mi/kW. I know this is lower than most, but it's because I drive the Leaf like any other car, without special considerations for power savings.


For Range, I'm having a harder time. I believe our long-term solution to this is a real Geek Screen with the numbers we crave: Instantaneous Watt consumption, true battery SOC, and some detailed representation of recent performance. This information is so massaged and 'interpreted' by the time it's presented on the Dash or Carwings, that it's nearly useless. The battery bars are the only thing with some basis in constants, and they're both non-linear and subject to change.

I will continue to seek the data via CANbus.

gascant said:

I like the term "Wall to Wheels" as it's very descriptive. I've been calling it "Consumed". Is there a standard term in the EV community?

Click to expand...

i have mine...

AMPK= AC miles per kwh which would be..."wall" power

DMPK= DC miles or "battery" power. but my acronym thread was not very popular so your YMMV on understanding while using these terms

so my efficiency is determined by DMPK/AMPK. the AMPK is measured and considered accurate and like yours i am right at 3.7 AMPK as well. the DMPK is determined by resetting the Leaf's meter which is accurate based on something i am assuming. not sure of my understanding of that, but it has been pretty much dead on consistent

DaveinOlyWA said:

AMPK= AC miles per kwh which would be..."wall" power

Click to expand...

We'll have to rethink this when someone starts DC Quick-charging, or direct-DC charging off Solar.

DMPK= DC miles or "battery" power.

Click to expand...

I can't use these units because I don't have a direct view of DC (battery output) kWh. Assigning specific units to something inferred, approximated, or variable just makes for confusing results later.

Miles we can measure accurately.
"Wall" kWh we can measure accurately at the source.
Battery kWh, that's still Nissan's secret. Because of this, charger efficiency is also a debatable ratio.

If I had a favorite summary unit, it would be:
Wall Watt-hours per Mile.
Consumed Watt-hours per Mile?
And for now, A/C Wh per mile.

Because MPG is still our unfortunate unit for ICE, mi/kWh is a natural analog. It's still upside-down, though.

For instantaneous readout on the dash, my favorite values would be:
- Useable Wh remaining in the Battery.
- Instantaneous Watts Per Mile

Bonus values:
- Average Watts per Mile for 1, 5, and 20 miles.
- Wh used from Battery since last charge.
- Instantaneous Watts

GroundLoop said:

I care about two things:

1) Cost per mile, which becomes Miles per kWh as a normalized measure. (I prefer Watts per Mile)

2) Useable Range, and predicted range while driving, because it impacts planning and useability

Click to expand...

GroundLoop - this is exactly what I've been saying. If we are truly interested in advancing the EV (LEAF and others), this is what people want to know. How much is it going to cost me to drive it? How far can I go? We need to educate others that the LEAF is a tool. You own a specific tool for a specific purpose.

It was recently called out in another thread that TRONZ owns a LEAF, an F350 SuperDuty, and a GSXR1000. Three radically different vehicles, yet I suspect that he bought each for three different purposes. When we discuss our LEAF with others, we always say that the LEAF is the perfect situational vehicle - but if your situation is not the same as ours it may not be the right vehicle for you. Then again, neither is an F350 or a GSXR1000. One day, EVs will go further and cost less. One day publicly available EVSE's will be abundant. One day, people will say "Why did it take so long?" What we can do now is to help others understand that the LEAF is a really great car. But it may not be the right car for you - yet.

LEAFguy said:

When we discuss our LEAF with others, we always say that the LEAF is the perfect situational vehicle - but if your situation is not the same as ours it may not be the right vehicle for you.

Click to expand...

Exactly.

Similarly, there are people for whom m/kwh or the usable battery capacity is important. May be not for others :lol:

JessEV said:

My assumption is that each bar represents 2kWh since there are 12 and it is a stated 24kWh battery.

Click to expand...

I thought I read that while it is a 24 kWh pack, not all of that is available for use. There's a 'protective cushion' at the top & the bottom, leaving about ~21-22 kWh effective (0-100% Soc). This is done to extend the life of the battery.

Herm said:

Some people could care less about CO2.. in any case power at my outlets is CHEAP, only $0.11 a KWh

Click to expand...

I imagine you meant "couldn't care less"?

Anyway, where do you get juice for $0.11/kWh? At PG&E, my "baseline" usage is 8 kWh, and my house draws about 20 kWh per day before I've even added a car. Server computer, waterbed, aquarium, freezer, networking gear, three kids... it adds up! And past baseline, I pay about $0.48/kWh. Makes solar installations start looking appealing, if my house wasn't surrounded by trees. (And the city has a tree preservation ordinance)

jwatte said:

At PG&E, my "baseline" usage is 8 kWh, and my house draws about 20 kWh per day before I've even added a car. Server computer, waterbed, aquarium, freezer, networking gear, three kids... it adds up! And past baseline, I pay about $0.48/kWh. Makes solar installations start looking appealing, if my house wasn't surrounded by trees. (And the city has a tree preservation ordinance)

Click to expand...

Can't you switch to PG&E's TOU E-9 rates for EVs? It's less than $0.06/kWh for off-peak usage.

SparkyEV said:

I thought I read that while it is a 24 kWh pack, not all of that is available for use. There's a 'protective cushion' at the top & the bottom, leaving about ~21-22 kWh effective (0-100% Soc). This is done to extend the life of the battery.

Click to expand...

It may be 24 kWh total, or maybe 27 kWh, or even more. It may be 24 kWh usable, or as little as 21 kWh, or possibly even less. There could be a 15% protective cushion, or maybe 20%, or only 10%, possibly even less than that. It's mostly all speculation at this point. We don't have enough facts to nail down the truth.

Ray

SparkyEV said:

jwatte said:

At PG&E, my "baseline" usage is 8 kWh, and my house draws about 20 kWh per day before I've even added a car. Server computer, waterbed, aquarium, freezer, networking gear, three kids... it adds up! And past baseline, I pay about $0.48/kWh. Makes solar installations start looking appealing, if my house wasn't surrounded by trees. (And the city has a tree preservation ordinance)

Click to expand...

Can't you switch to PG&E's TOU E-9 rates for EVs? It's less than $0.06/kWh for off-peak usage.

Click to expand...

It's not nearly that simple. In the first place there is E-9a and E-9b. E-9b has some very hefty startup costs. E-9a means the EV is sharing the tier allotment with the rest of the house. If jwatte is paying $0.48, they must already be using something like E6 TOU and be at tier 3, and he is quoting the peak rate. Peak rate tier 3 for E-9a is $0.46, nearly as bad. And tier 3 off peak is $0.15, not $0.06.

Ray

planet4ever said:

It's not nearly that simple. In the first place there is E-9a and E-9b. E-9b has some very hefty startup costs. E-9a means the EV is sharing the tier allotment with the rest of the house. If jwatte is paying $0.48, they must already be using something like E6 TOU and be at tier 3, and he is quoting the peak rate. Peak rate tier 3 for E-9a is $0.46, nearly as bad. And tier 3 off peak is $0.15, not $0.06.

Ray

Click to expand...

That's true, I was quoting tier 1 rates and I should have been more clear about that in my post. I plan on going with E9-B myself, in order to keep most of the EV usage in tier 1. The upfront costs are $250 for the meter plus the cost to have an electrician install a second panel. I expect to recover these costs in the first year because of the advantage over sharing the baseline with the rest of the house under E9-A.

In any case, jwatte could do much better than $0.48/kWh with no additional costs by switching to E9-A and charging during off-peak hours.

SparkyEV said:

Can't you switch to PG&E's TOU E-9 rates for EVs? It's less than $0.06/kWh for off-peak usage.

Click to expand...

That would not save me money, because the peak time draw (which is when AC and kid computers run and whatnot) would be billed at a higher rate.
I'm looking at E-9B rates, with the option of a second meter (although the installation charge for that -- ouch!)
What I don't understand is that the rate goes all the way up to Tier 5 for the E-9B. Peak use at Tier 5 is $0.57 with that rate!

Given the $4k install for a second meter, though, I probably should put in a kilowatt or two of PV solar instead -- would probably pay itself back sooner