Miles per kwh so far... my calcs vs. the LEAFs calcs

there maybe other KAWs out there, but mine is only good for 120 volt for current measurement. i have had it near 15 amps before but only briefly. have been up to 1714 watts before. i know this because i took a picture of it once and saw that. did not notice it when i took the pic so dont know how long it had been that high. i normally see it in the 1300-1400 range.

but either way. so far total miles 68, total K's 23.19 so just under 3 mpk. now that is wall to wheels. i really dont care about anything else, since that is "MY" cost.

with connection charge, taxes, etc my cost is around 10.2 cents/kwh. so i am just over 3 cents a mile so far. but the real numbers start now. just as the first tank from the dealer on my Prius was short. this one will be as well. as long as i was at the dealer, i should have plugged in but did not think of it at the time. oh well. but now i am full and we shall see what happens now.

i am beginning to think that charging efficiency is not going to be so good. to test, i will not be preheating (its about 37º outside, around 47 inside my garage so it will be a bit of a sacrifice!!) so i can get a better idea of the efficiency to wheels from battery.

Had an almost 2 minute power outage last night (around 5:30 per my UPS status report) after the car was fully charged. At 7:30 all blue lights on the dash were off. Is it normal that they go off once (or a while after) reaching 100% charge ? Or should they stay on until you unplug ?

LEAFer said:

Is it normal that they go off once (or a while after) reaching 100% charge ? Or should they stay on until you unplug ?

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From page CH-26 of the manual:

When fully charged
All of the indicator lights 1 to 3 illuminate when:
. The Li-ion battery is fully charged
. 80% of a charging timer is completed
. When 90% of a quick charge is completed
The indicator lights turn off after approximately 15 minutes or when the charge connector is removed.

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Thanks. I will pick up a manual (or the PDF) one of these days :lol:

Ok I did not read the manual since I never do but I was guessing with the last light blinking we were charging the last 20%. Knowing u r at 90% is good to know..

Not so sure ... because it says QUICK CHARGE ... the final blue light indicates at 90% as opposed to 100%. For normal charge (L1 & L2) I assume that means the final blue light is still blinking anywhere from 67% - 99%. Unless you are using a timer, in which case that final 3rd light turns solid at 80% (and probably blinks between 67%-79%, but that's a guess).

(Kind of confusing ... I'd rather not see a difference for indicators between timed- and un-timed charging.)

just an update; yesterdays commute 20.3 miles, recharged 6.18 kwh, mpk 3.28

scenario; normal commute with short detour. all at 40 mph or less. temps mid 40's. based on a 19.2 kwh pack and my estimated 106 mile range which would imply a mpk from pack to wheels of 5.52 mpk

if using 90% then that is 4.90 mpk.

that leaves a pretty pathetic charging efficiency (obtw, the plug uses about 10 watts while plugged into nothing)

so am i missing something? will continue to monitor...obtw, carwings not working, should have it fixed today at Olympia Dealer. that should give me more to work with.

leafme said:

This 33% (67% savings) is based on regular gas at $3.10/g, a mpg of 45, the LEAF costing 0.0227 $/mi at a super off-peak tariff rate of 0.075 $/kwh (midnight to 5am, 0000-0500 hrs, for SDG&E).

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Of course, if you figure the cost of a 36mo/12k lease is about $0.50 a mile, then you might as well get out of the slow lane and drive it like bodengroden's wife.
:twisted:

DaveinOlyWA said:

based on a 19.2 kwh pack and my estimated 106 mile range which would imply a mpk from pack to wheels of 5.52 mpk

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I believe that is a misconception. It seems to be pretty well established that the total usable capacity of the battery is about 24 kWh, although that does work out to about 19.2 kWh for 80%, or, if you prefer, from 10% to 90%. But you don't charge between 10% and 90% of usable capacity. The 106 mile estimate is from wherever you are (presumably 100%) down to 0%. It is how far the computer thinks you may be able to go if you run the car down past the Low Battery warnings, down past the heat/AC power limitation, down past the turtle mode, until it finally comes to a stop. i.e. it is how far you can go on 24 kWh, not 19.2 kWh.

Using that basis, the computer is saying that battery to wheels will be 4.42 mpk. You got 3.28 mpk wall to wheels, which is only about 75% efficiency. Still very bad, though not as bad as you thought. However, you shouldn't assume this is all charging system inefficiency. Some of it is probably due to incorrect estimation in the computer program that is trying to guess how well you will drive before you start your day's trip. Also, with temps in the mid 40s weren't you using the heater? Surely that 106 mile range was their estimate with climate control off.

Well then if we assume that the estimate is based in the entire 24 kwh then we are still over 5 over 5 miles per kwh

now that i have enough data to make one, i am creating an excel sheet (actually open office calc) to track progress since i dont have Carwings working yet.

as i was generating columns a thought came to me; i am reseting the MPK estimate from the car daily (thought about per trip, but without charging, it would be valueless) and was using that divided by MPK estimate from the wall (AC-MPK...make that AMPK the other DMPK) in an attempt to get a guideline on charger efficiency, but without knowing the value of the trees (the more trees, the lower the efficiency) that would be less meaningful as well.

so perhaps the inverse would give me an indication of how much more of a role regen played?

i am trying to verify how efficiently the charger is working and not getting good numbers here. now the only thing i seem to be missing is how much power the climate controls use. i am not finding them on the carwings website. everything else seems to be listed.

any one know where or is it even available. i would think that to be very unusual considering all the details carwings does provide

DaveinOlyWA said:

i am trying to verify how efficiently the charger is working and not getting good numbers here. now the only thing i seem to be missing is how much power the climate controls use. i am not finding them on the carwings website. everything else seems to be listed.

any one know where or is it even available. i would think that to be very unusual considering all the details carwings does provide

Click to expand...

Log in to the owner's portal
'launch CARWINGS''
select Driving History from the menu bar (adjacent to the Home icon)
select My Driving Style (second item on the sub-menu line at the top)
You'll see detail for the most recently recorded day, and at the bottom, a scrollable table (Past Records) which shows other days, with 3 values, Electricity consumed by the traction motor, captured by regenerative braking, and consumed by vehicle accessories. The climate control usage is reflected in that third category. Yes, it has "other things" in it as well, but you can extrapolate how much that additional relatively constant load might be by examining days when you didn't use climate control. (We generally aren't using climate control so our accessory figure is typically .2 per day for anywhere from 25-35 miles of driving)

ok i have seen the accesories category but it does not reflect what i had expected. the 28th, it listed only 1.5 kwh used and this would be a trip that had heat/defrost for nearly all of the 57 miles traveled
verses the previous day where i only pulsed defrost on once in a while to clear the windows but had the radio running most of the time along with charging my cellphone.

i have to say, my figures are plausible but climate controls seem not to be included. now because of the hiccups i had with getting carwings started, i only have 2 days to review. i guess we will see what happens down the line.

Is the energy "consumed by the traction motor":
1. the TOTAL consumed, part of which came from the WALL, and some came from REGEN.
2. or, the NET energy consumed, total into the motor (or inverter) minus the Full Regen'd amount (that is used to re-charge the battery)?

The "used" kWh (reported by some) does not appear high enough to be #1.

The Full Regen amount is almost like From-Wall energy, it has losses going into the battery, and losses coming back out of the battery for use. The anount out would be Reclaimed-Regen, always significantly less than the Full Regen amount.

So, 4 kWh of Full Regen might only provide 3 kWh of "motor" power (Reclaimed-Regen).

Assuming 11 (net, #2) used and 4 Regen (only 3 recovered for use), the actual Total motor usage might be 11+1=12, not just the 11 "reported".

Does that help explain the "strangeness" of some CARWINGS numbers?

Of course, not properly including A/C or Heating in the "acc" amount might also explain some things.

garygid said:

The "squared" increase in energy usage for the aerodynamic drag applies only to the portion of the energy being used to overcome aero-drag.

So, if the aero-drag is about 50% of the total, then only that part goes up by 21% when the speed increases by 10%.

The part (maybe 30%) that is velocity-related (like rolling resistance) only goes up by 10%.

And the Heater and other "constant" energy uses do not increase ... their energy usage PER MILE actually decreases, since you are shortening your trip with the higher speed.

So, a 10% increase in speed typically does not require 21% increase in energy, at least until speeds at which the aero-drag becomes the dominant energy-hog!

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The aero drag is the dominant energy hog quite early on (40-45+ mph??). My guess is the aero drag is MUCH higher that 50% above that. I mean what else is there? Some wheel rolling resistance, wheel bearing resistance, slight increase in motor losses? What else am I missing? Can't imagine those amount to a whole lot (but maybe I'm wrong).

Malcolm

http://craig.backfire.ca/pages/autos/drag

Carwings has been telling me I have been getting 5.7 miles/kwh. So i thought I should check this against reality. I've been charging to 80% using the timer. Yesterday I drove 27.9 miles. I hooked up the trickle charger to a kill-a-watt and charged the car back to 80%. It took 9.86 kWh to do this. This is 2.8 miles/kWh. I'll keep track over a longer period but a suspect this trend will hold.

Observations:
1. apparently I should just take the Carwings figures and divide by two.
2. Where I live electricity is $0.27 /kWh at the moment. So the 2.8 miles/kWh translates to 0.095 $/mile. I traded in my 2002 VW Golf TDI for the LEAF. It got 42 miles/gal. Currently Diesel is $3.88/gal here so that comes out to 0.092 $/mile. So, my fuel costs are slightly more per mile by going with the electric car. So much for the electric car yielding fuel savings!

Question:

These results are based on using the level 1 trickle charger. Is there any reason to believe my results will be any better using the level 2 charger (I don't have an easy way to measure the current consumed by my level 2 charger)?

akohekohe said:

These results are based on using the level 1 trickle charger. Is there any reason to believe my results will be any better using the level 2 charger (I don't have an easy way to measure the current consumed by my level 2 charger)?

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People "seem" to be getting slightly lower wall-to-wheels efficiency using only the L1 charger. It's quite likely that the on-board charger is less efficient at converting 120V AC to 400V DC than 240V AC to 400V DC. Most power supplies I have seen that handle dual voltages are slightly less efficient on 120V. I don't know that anyone has tested both with accurate enough equipment. Certainly 2.8 mi / kWh seems to be a bit low compared to what others seem to be reporting.

1. You are measuring kWh from the wall, whereas CARWINGS is attempting to show the energy (again kWh) recovered OUT of the battery. So, the CARWINGS figure is ignoring the following three significant losses:
a. in the charger,
b. in the battery while putting energy in,
c. in the battery while recovering energy from the battery.

2. It appears to me that the CARWINGS calculation of the energy used contains an error, most likely in how Regen Energy is handled, subtracting it almost twice. This makes it seem like the energy used us substantially smaller than it actually is, so their mi/kwh is much too high, especially when there has been a lot of regeration on the "trip".

I think that both these issues contribute to the Hyper-Efficient numbers we see on CARWINGS.