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Ingineer
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Leaf Charging Efficiency - Lab Test (and Idle power draw)

Tue Apr 17, 2012 9:15 pm

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
Easily Learn Electricity HERE! - - - - Website: http://evseupgrade.com/ - - - - Like us on Facebook: EVSE Upgrade

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Nubo
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Re: Leaf Charging Efficiency - Lab Test (and Idle power draw

Tue Apr 17, 2012 9:35 pm

Do you know the power draw of the coolant pump? When I was charging at 120V there was barely any detectable warmth in the coolant hoses, yet the pump seems to run continously. At 240V there is noticeable heat. I'm just wondering if the pump varies its speed based on the heat load. Seems like it wouldn't need to run so hard during 120V charge.
I noticed you're still working with polymers.

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Re: Leaf Charging Efficiency - Lab Test (and Idle power draw

Wed Apr 18, 2012 12:39 am

Any idea what the power factor was charging at 120V vs 240V?

Kind of curious that it appeared to be pulling at least 12.75A on 120V and 15.66A on 240V. I wonder if it bumped up the current while on 120V because of the voltage sag? I know you've mentioned seeing that before. Would be interesting to see what it does when the input voltage varies.

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Ingineer
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Re: Leaf Charging Efficiency - Lab Test (and Idle power draw

Wed Apr 18, 2012 12:51 am

The coolant pumps (there are 2) run all the time while charging, pump one runs at 39% duty-cycle and pump two runs at 44%. The speed does not change regardless of charging power, which is why there is significant fixed overhead while charging. Why this was chosen by Nissan is a mystery.

The Power factor varies but is almost always above .96 and usually .99 or better.

Yes, the Battery ECU decides what the charge power limit should be and the charger obeys. So if you have higher line voltage, you'll have less amps, but you won't ever increase power.

-Phil
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Re: Leaf Charging Efficiency - Lab Test (and Idle power draw

Wed Apr 18, 2012 12:56 am

Ingineer wrote:Yes, the Battery ECU decides what the charge power limit should be and the charger obeys. So if you have higher line voltage, you'll have less amps, but you won't ever increase power.

Any idea how low the voltage can get before the car decides that voltage is too low? For example, if AC input voltage is 100V will it increase current draw to 14A even though the EVSE is telling it not to exceed 12A? How low will it let the voltage get before giving up completely?

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Re: Leaf Charging Efficiency - Lab Test (and Idle power draw

Wed Apr 18, 2012 1:09 am

drees wrote:Any idea how low the voltage can get before the car decides that voltage is too low? For example, if AC input voltage is 100V will it increase current draw to 14A even though the EVSE is telling it not to exceed 12A? How low will it let the voltage get before giving up completely?
I haven't performed a LVCO test, but I can tell you that the charger was engineered to work on Japan's power system which is 100/200VAC rather than the 120/240VAC we have here. This likely means it's good down to at least 90 if not lower.

The charger usually obeys the EVSE's Pilot signal within about .5 amps. For this test I had the Pilot signal overridden to about 32% duty cycle (or about 19.2a limit) to see what would happen with some sag. Even with this, The charger simply will not pull much more than my tests show at low voltages likely due to the transformer winding specifications. On the Rev2 EVSE we sell, the Pilot is actually set to 16.5a, but you still don't ever see anything over 13 because of this hardware issue.

-Phil
Easily Learn Electricity HERE! - - - - Website: http://evseupgrade.com/ - - - - Like us on Facebook: EVSE Upgrade

garsh
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Re: Leaf Charging Efficiency - Lab Test (and Idle power draw

Wed Apr 18, 2012 2:17 am

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

Can you put together a list to answer the question I posed here?
I was curious about the power draw of as many of the Leaf's systems as you may have measured.
I was a bit stunned the first time I turned on the windshield wipers and saw the rather significant jump the accessory power meter made. :o
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edatoakrun
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Re: Leaf Charging Efficiency - Lab Test (and Idle power draw

Wed Apr 18, 2012 10:02 am

Does a stop-and-start event, draw any additional power?
no condition is permanent

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Ingineer
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Re: Leaf Charging Efficiency - Lab Test (and Idle power draw

Wed Apr 18, 2012 10:58 am

The accessory power meter is a "fake" meter. It simply adds on some pre-coded amount of power when it detects you have turned somehing on (via the CAN bus). So it will not show the actual power draw, nor will it show many accessories, such as anything drawing power from the 12v outlet. Do not depend on it for making any calculations.

Here's a rough list of the biggest consumers in the order I am guessing they consume power in:

Drive System
PTC Heater (Climate Control)
A/C Compressor (Climate Control)
Radiator/Condenser Fan
Fan (Climate Control) varies greatly depending on speed.
Power Steering Motor (when doing lots of low speed maneuvers)
Windshield Wiper (Varies depending on speed)
Rear Defroster (+ side mirrors)
Heated Seats
(Base ~160w Leaf Load - Cannot turn off!)
Halogen High Beams
Average Laptop plugged into 12v accessory jack
Heated Steering Wheel
Led Low Beams
Exterior Marker Lighting
Stereo System - Audio part only (Assuming normal listening levels)

I have not measured these independently, I am basing this on my experience and knowledge as an Engineer. The Nav/MFD is always on and it makes almost no difference if you are actually listening to something at low levels or have the system "off".

A "start/stop" event doesn't drain much additional power, the 12v aux battery charge algorithm is reset, so there is a momentary pull to top off the 12v battery, and the brake system does a test, other than that there is not much that occurs during startup that draws power. So if you are making a decision of whether to leave your Leaf on while you run into the house for a few minutes, it's almost always better (power wise) to shut it off. I would imagine even 60 seconds of being off negates any extra consumed during "start". The bigger reason is safety and security. If you jump out of a Ready Leaf, anyone can jump in and take off, even without your keyfob.

-Phil
Easily Learn Electricity HERE! - - - - Website: http://evseupgrade.com/ - - - - Like us on Facebook: EVSE Upgrade

charlie1300
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Re: Leaf Charging Efficiency - Lab Test (and Idle power draw

Wed Apr 18, 2012 11:03 am

Phil, thanks for posting this useful info.
Let me just ask if I'm understanding it correctly. If I'm charging with your rev2 upgrade EVSE at 240V (90.9% efficiency) and car wings says that my last trip consumed 3.2kwh, does that make my wall to wheel consumption 3.52kwh? (3.2/.909 = 3.52)
My assumption is that car wings tells me what I drew from the battery.
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