leafme
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Electrical charging - measured results, 120v vs. 240v

Sun Jan 09, 2011 10:59 pm

Measured my LEAF tonight while charging to get a feel for the power input for 120v and 240v EVSE conditions.

Equipment used:

P3 International P4400 Kill A Watt, 15a, 120v electricity usage monitor (primarily for power factor, PF)
Fluke 289 True RMS recording multimeter
Fluke i410 AC/DC current clamp
Fluke T5-600 Volt/Amp/ohm meter

Used all equipment to verify consistency which was within approximately 1%. Assumed the Kill A Watt power factor was accurate and used its value for calculating power when using Fluke measured values at 240v.

The power factor indicated 0.98. A power factor close to 1 is expected since we are just charging a battery here and no reactive load is expected.

The Kill A Watt indicated 120.4v, 11.94a and 1,406w with PF of 0.98. It fluctuated over the few minutes I measured it but stuck very close to 1400-1420w. This is a good thing since the plug on the portable EVSE is rated 120v, 15a. The NEC limits continuous loads to 80% of equipment rating (unless equipment is rated for 100% loading which almost nothing is) which equates to the 12a continuous load I measured (11.94a). While the manual does indicate a 20a branch circuit is needed, errata supplied with the owners package corrects this indicating only a 120v, 15a branch circuit is necessary. Good thing since the plug on the portable EVSE is a 15a plug NOT a 20a plug. At 120v, 12a, 0.98 PF, you can squeeze 1,411w out of the wall as input to the LEAF. As the charge begins, the LEAF smoothly ramps the current up from 0a to 12a in 5 seconds. A nice smooth ramp up. Nice job on that design Nissan. Fairly easy to do with power converter technology but at least they chose to do it.

To measure the 240v EVSE supply on my garage wall I used the Fluke 289 and the i410 current probe and verified the measured values with the T5-600 and assumed the power factor to be the same, 0.98. This indicated 15.55a and 245v which yields 3,809va or 3,733w. This too ramped up in 5 seconds from zero. After about 3-5 minutes the current settled out at 15.67a, 243v or 3,731w. Nissan also kept this rate at under the 16a max current allowed on a 20a branch circuit by code even though my EVSE and installed 40a branch circuit is capable of 32a at 240v. As an fyi, the Blink is rated at a maximum of 240v at 30a. This "larger" branch circuit provides the capability to charge at almost twice the 3,733 rate in the future if I choose to upgrade the power converter in the LEAF when Nissan releases the upgrade in a couple of years. Mark Perry told me its coming but I knew better than to ask him the price at this time.

So what we see here is 1,410w for the 120v EVSE and 3,771w for the 240v EVSE or a ratio of 0.37, or (1/x) at 2.67. This is to say the 120v EVSE will charge at 37% of the 240v EVSE rate or the 240v EVSE will charge at 267% of the 120v EVSE rate. In any case, the indicator in the car usually states a 3 or 4 to one difference (and only estimates to the half hour).

As you can see here, my measurements indicate a 2.67 to one ratio. Extending these measurements to miles (range) gained per charge time, and noting that Randy and I got 18 miles for 1.5 hr of charge on our "111 mi trip" (12 mi/hr), I would expect the 120v EVSE to boost the battery by 12/2.67 or 4.5 mi/hr. If I come across a single phase power meter I'll verify the power factor at 240v (but I bet it's very close to the same at 0.98).

For general travel planning purposes, I plan my trips for non-eco driving, add 5-6 miles for good measure (I call it anti-walking measure) and then drive almost 100% of the time in eco mode with the climate control in auto. I've only owned my LEAF since Tuesday so I'll need a few more travel data points to draw conclusions on my forecasting ability but for now, I haven't had to walk yet.

Owning and driving an electric car does take a different mindset. But so far, man, this is a blast.

Malcolm :geek:

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Re: Electrical charging - measured results, 120v vs. 240v

Sun Jan 09, 2011 11:27 pm

Thanks for that report. And good to know the LEAF will not cut off at 3.3kW. It actually got you 14% more than expected :P

So ... rather than limiting to 3300/243 = 13.58A, and seeing a 30A max pilot signal, the LEAF's charger allowed almost the full 16A. I wonder what will happen at a public charging location with 208V nominal (not 240). Will the LEAF charge at 16A (almost) also (3328W), or increase the current a little to reach a similar 3731W ?
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Lost CapacityBar 6/6/13 @34,173 miles while in LEAF Battery Monitor: 83.41%, 71.4F (avg); cool overnight;

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walterbays
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Re: Electrical charging - measured results, 120v vs. 240v

Sun Jan 09, 2011 11:44 pm

leafme wrote:Measured my LEAF tonight while charging to get a feel for the power input for 120v and 240v EVSE conditions.
This is great information! Thanks for taking such careful measurements and writing it up for everyone's benefit.
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leafme
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Re: Electrical charging - measured results, 120v vs. 240v

Sun Jan 09, 2011 11:45 pm

LEAFer wrote:Thanks for that report. And good to know the LEAF will not cut off at 3.3kW. It actually got you 14% more than expected :P

So ... rather than limiting to 3300/243 = 13.58A, and seeing a 30A max pilot signal, the LEAF's charger allowed almost the full 16A. I wonder what will happen at a public charging location with 208V nominal (not 240). Will the LEAF charge at 16A (almost) also (3328W), or increase the current a little to reach a similar 3731W ?
My measurements were input power to the LEAF power converter. Assuming the battery charge cycle and the power converter have a combined efficiency of about 85%, there is likely around 3.3kw actually increasing battery state of charge. Not sure these are exact values but you get the idea. Of course we don't know exactly how Nissan characterized their 3.3kw value but this could explain their 3.3kw language (but of course I'm just guessing here).

As to how Nissan designed the battery charge power converter I don't know. I could guess at 16a max but as soon as I did I could easily be wrong.

Malcolm :geek:

leafme
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Re: Electrical charging - measured results, 120v vs. 240v

Sun Jan 09, 2011 11:56 pm

walterbays wrote:
leafme wrote:Measured my LEAF tonight while charging to get a feel for the power input for 120v and 240v EVSE conditions.
This is great information! Thanks for taking such careful measurements and writing it up for everyone's benefit.
My pleasure walterbays. My adoption of the geek icon was not random. Just trying to move the knowledge forward with what I can contribute as all of us on this forum are trying to do (which is why this is such a cool forum).

Malcolm :geek:

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Re: Electrical charging - measured results, 120v vs. 240v

Mon Jan 10, 2011 12:09 am

Great information, Malcolm. Thanks!
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Re: Electrical charging - measured results, 120v vs. 240v

Mon Jan 10, 2011 8:57 am

leafme wrote:
LEAFer wrote:Thanks for that report. And good to know the LEAF will not cut off at 3.3kW. It actually got you 14% more than expected :P

So ... rather than limiting to 3300/243 = 13.58A, and seeing a 30A max pilot signal, the LEAF's charger allowed almost the full 16A. I wonder what will happen at a public charging location with 208V nominal (not 240). Will the LEAF charge at 16A (almost) also (3328W), or increase the current a little to reach a similar 3731W ?
My measurements were input power to the LEAF power converter. Assuming the battery charge cycle and the power converter have a combined efficiency of about 85%, there is likely around 3.3kw actually increasing battery state of charge. Not sure these are exact values but you get the idea. Of course we don't know exactly how Nissan characterized their 3.3kw value but this could explain their 3.3kw language (but of course I'm just guessing here).

As to how Nissan designed the battery charge power converter I don't know. I could guess at 16a max but as soon as I did I could easily be wrong.

Malcolm :geek:
Sure thing ... I wasn't implying that there is no loss, just good to see that from a wall AC perspective we are apparently blessed with 3.7 not 3.3kW (subject to additional corroboration). Wall-to-battery (miles per hour charged) is still open (actual measurement).
2011 Silver SL+QC [Mfg: 11/2010] 36mo/15k LEASE
06Jun2013 Status [28.5 months][34,173 miles][11 bars]
Lost CapacityBar 6/6/13 @34,173 miles while in LEAF Battery Monitor: 83.41%, 71.4F (avg); cool overnight;

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wsbca
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Re: Electrical charging - measured results, 120v vs. 240v

Mon Jan 10, 2011 4:56 pm

LEAFer wrote: Wall-to-battery (miles per hour charged) is still open (actual measurement).

Here's a data point:

Yesterday we drove 22.1 miles (with 4 adults in the car, in Eco, being rather gentle but including a bit of freeway and some climbing/descending - basically a typical San Diego area trip). Carwings reports net consumption of 4.2 kWh (5.6 kWh to the motor - 1.7 kWh regen + .3 kWh accessories).

Last night's recharge to 80% (10 bars, reported as 83%), which is also where we started yesterday morning before the drive in question (i.e. after an identically configured charge the night before) took exactly 1:48 (1.8 hours.) Malcolm reports that the Clipper Creek unit (which I also have) sucks up 3771w continuous, implying I pulled 6.8 kWh from the wall.

22.1/6.8 = 3.25 Miles per (wall) kWh.

So the car thinks it used 4.2, but I fed it 6.8. That's a little bothersome because it implies the overall charging efficiency is only 62%. A far cry from 85%, and it may result in real world electric bill vs. car mileage measurements that don't jibe with the cost per mile claims being made in the marketing literature.

On the other hand, the bottom line figure of 3.25 miles/purchased (or solar generated) kWh isn't completely horrifying.

Disclaimer...this is ONE trip and ONE matching recharge and I know there are unaccounted for variables...but I believe those variables may be somewhat minor and I won't be surprised if this is about where things end up when we get more data.

EDIT: whoops - I think I misinterpreted Malcolm's data. The 3771W was from the EVSE into the car - I was assuming that was downstream of the meter, before the EVSE. So if it's even more going into the EVSE, with some losses within that device and the cabling, the 3.25 is going to drop further....
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planet4ever
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Re: Electrical charging - measured results, 120v vs. 240v

Mon Jan 10, 2011 6:01 pm

Though of course if there is some taper off even before you get to 80% that would make the numbers look better. I think I'd like to hear what someone's TED says rather than depend on back calculation from a wall clock.
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garygid
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Re: Electrical charging - measured results, 120v vs. 240v

Thu Jan 13, 2011 4:01 pm

The wall clock is only helpful if the current usage is constant.

However, from graphs of the current, the LEAF takes a substantial "siesta" before the last "burst" of charging.

Thus, the constant-current assumption that you were using is substantially wrong, especially for short-duration charges like your 1.8 hour charge. Perhaps 0.4 hours were "siesta" (zero current), and another 0.4 hours with the current tapering off (perhaps averaging 75% of full current).

During the "siesta", the cells MIGHT be doing some voltage-equalizing.
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