ldallan
Posts: 32
Joined: Mon Jan 16, 2017 10:15 am
Delivery Date: 31 Dec 2016
Leaf Number: 000000

Near Turtle to cells balanced: 20.8 kW with 2015 Leaf with 24 kW battery: Low kW? As expected? Battery losing capacity?

Sun Feb 25, 2018 8:48 pm

2015 Leaf with 24 kW battery, 30,400 miles, 12 bars.

I plugged my Leaf into a ChargePoint station. It was in Very Low Battery status near the point of "Turtle Mode". The Range and Percentage values had both been blinking for several miles. I generally avoid letting the battery get that low, other than for tests.

I left the Leaf charged in for nearly 5 hours, to let it go through its monthly "Cell Balancing". My understanding is that "cell balancing" about once a month is recommended as "best practice" for battery life and/or performance.

I use the ChargePoint app on my Android device, but not LeafSpy. The app and the ChargePoint head LCD screen showed 20.8 kW put into the Leaf. Another factor is that there are some inefficiencies with 220v charging from heating and inverter losses, so that all 20.8 kW wouldn't actually get into the Leaf's Li-Ion battery. There were also some losses from "cell balancing" with the highest cells being drained several times.

I'm pondering how to interpret that.
  • I was expecting something like 25+ kW, reflecting losses from the charger thru the inverter to the battery
  • As expected ... the 24 kW rating is optimistic
  • reserve capacity ... there is less that 24 kW actually available
  • battery capacity is declining, and the 12 bar indicator may be getting closer to losing a bar to 11

cwerdna
Posts: 8396
Joined: Fri Jun 03, 2011 4:31 pm
Delivery Date: 28 Jul 2013
Location: SF Bay Area, CA

Re: Near Turtle to cells balanced: 20.8 kW with 2015 Leaf with 24 kW battery: Low kW? As expected? Battery losing capaci

Mon Feb 26, 2018 1:07 am

First off, get your units right. Leaf has a 24 kWh battery but only about 21 to 22 kWh are user accessible on a new battery. There's some inaccessible at the top and bottom. As it degrades, there's less capacity.

kW and kWh are very different metrics. It's the same as confusing gallons with horsepower. Think of kW = horsepower, kWh = gallons.

If one charges at 1 kW (or 1000 watts) for 6 hours, 6 kWh came out of the wall. If it's at 6 kW for 1 hour, it's also 6 kWh. If it's 1 watt for 6000 hours, it's also 6 kWh.

Watts or kilowatts are measure of power. Watt-hours are a measure of energy.

One pays for electricity at home in cents per kWh. There are a few utilities w/residential plans where they not only bill per kWh but also have demand charges, but that's rare and complicates calculations. (Demand charges aren't unusual on many commercial plans.)

You'll notice that Chargepoint's UI has the correct units: kW for power and kWh for energy dispensed. There's also no 220 volts in the US. It's 120 or 240 volts. 208 volts is common for commercial power and thus many public and workplace L2 EVSEs actually run at 208 volts.

Your 20.8 should be kWh, not "kW".

(BTW, 1 hp = ~0.746 kW. And, many .gov sites say 1 gallon of gasoline=33.7 kWh.)

And, yes, not all the energy coming out of the "wall" makes it into the battery. There are charging losses (e.g. to run pumps, inherent in the on-board charger, besides numerous places where energy is "lost" as waste heat, including in the battery). Also, you didn't run the car low enough. If you wanted a more accurate measure, you should've run the car to below turtle, to when the contactor opens and the car won't move.

'13 Leaf SV w/premium package (owned)
'13 Leaf SV w/QC + LED & premium packages (lease over, car returned)
'06 Prius

Please don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

finman100
Posts: 328
Joined: Thu Sep 20, 2012 10:42 am
Delivery Date: 06 Jun 2014
Location: Albany, OR

Re: Near Turtle to cells balanced: 20.8 kW with 2015 Leaf with 24 kW battery: Low kW? As expected? Battery losing capaci

Mon Feb 26, 2018 12:13 pm

seems about right. My 2014 SV with 43,000 miles is down a bar and I regularly get 18.5 kWh from empty to full and balanced.
empty is when there are dashes on the dash GOM (1 kWh left in the "tank" per Leafspy).

full is 100% charge and Leafspy showing 18.5 kWh.

Hopefully that helps.
Albany, Oregon
2014 Silver SV with charge/LED package. June 2014, I'm in the EV game!
46,000 miles
17.5 kWh on 100% charge (51-ish Ah), down 1 bar
4.2 miles/kWh average
Best trip: all of 'em. They're all no-gas!

ldallan
Posts: 32
Joined: Mon Jan 16, 2017 10:15 am
Delivery Date: 31 Dec 2016
Leaf Number: 000000

Re: Near Turtle to cells balanced: 20.8 kW with 2015 Leaf with 24 kW battery: Low kW? As expected? Battery losing capaci

Mon Feb 26, 2018 3:24 pm

Thanks for the replies.

And "guilty as charged" as far as having measurements confused between kW and kW-Hr.

I'm curious what "when the contactor opens" means.

  • The GOM starts blinking with "---" when there is about 8% left on the "Percent Remaining" read-out.
  • The "Percent Remaining" starts blinking with "---" when it reaches lower than 5% remaining.
  • In reasonable weather between about 50° to 80° F, the Leaf can go about 10 miles further before reaching "Turtle Mode".
  • ...
  • In the test I did at about 10° F, there may have been 5 or 6 more miles before "Turtle Mode" would have shown up.

FWIW:
We got our Leaf as a 2 year lease turn-in with 14,500 miles at the end of December, 2016 during a cold spell of -5° F. The first several weeks were an unpleasant learning curve. Less range that expected and longer charge times. For a while we were thinking "have we made a big mistake?" But once the weather got warmer and our expectations got more realistic, we've gotten to be relatively pleased with it.

Plus, it depreciated like a rock during the cold snap ... the dealer knocked off an additional $3000 and seemed to "throw in the towel" and was prepared to auction it off.

I've done tests down to "Turtle Mode", but i was staying near a charger, and didn't go more than several blocks once "Turtle Mode" was reached. The Leaf was definitely down in power ... having the go-pedal to the floor only resulted in about 3 or 4 circles showing.

Levenkay
Posts: 495
Joined: Mon Sep 26, 2011 10:01 pm
Delivery Date: 11 Aug 2018
Leaf Number: 308382
Location: Portland, OR

Re: Near Turtle to cells balanced: 20.8 kW with 2015 Leaf with 24 kW battery: Low kW? As expected? Battery losing capaci

Mon Feb 26, 2018 10:07 pm

ldallan wrote:I'm curious what "when the contactor opens" means.
The "contactor" is an extremely robust relay that, by default, disconnects the main Li-ion battery from pretty much everything except whatever microscopic drain the cell voltage sensors inside the battery represent. The contactor relay must be energized in order for the car's systems to access its main (aka "traction") battery, and this is done using power from the 12V system.

cwerdna
Posts: 8396
Joined: Fri Jun 03, 2011 4:31 pm
Delivery Date: 28 Jul 2013
Location: SF Bay Area, CA

Re: Near Turtle to cells balanced: 20.8 kW with 2015 Leaf with 24 kW battery: Low kW? As expected? Battery losing capaci

Mon Feb 26, 2018 11:16 pm

ldallan wrote:I'm curious what "when the contactor opens" means.

  • The GOM starts blinking with "---" when there is about 8% left on the "Percent Remaining" read-out.
  • The "Percent Remaining" starts blinking with "---" when it reaches lower than 5% remaining.
  • In reasonable weather between about 50° to 80° F, the Leaf can go about 10 miles further before reaching "Turtle Mode".
  • ...
  • In the test I did at about 10° F, there may have been 5 or 6 more miles before "Turtle Mode" would have shown up.

Contactor hasn't opened yet. I believe the contactor will open somewhere past turtle if the lowest cell drops below a certain critical voltage, to help protect the battery. (There's been debate as to what that value is, which may depend on the model year of car/revision of battery and likely is different on the 30 kWh and 40 kWh batteries vs. 24 kWh.)

You find find earlier discussion by Googling for site:mynissanleaf.com contactor open.

In Edmunds testing at https://www.edmunds.com/nissan/leaf/201 ... r-end.html, when doing 35 mph, it looks like they hit VLBW (2nd warning) at 122.0 miles. Turtle came on a 130.0 miles and I'm guessing the contactor opened at 131.2 miles, at which point they steadily lost speed until car halted at 132.0 miles.

They also said
It took 26.08 kWh of juice to recharge the battery, which works out to a consumption rate of only 19.8 kWh per 100 miles. The most we'd ever put in previously was 24.35 kWh, after a real-world random drive of only 71.2 miles and a DTE reading of 7 miles.

However, the OBC on an '11 and '12 Leaf is TOTALLY different than the one on a '13 to '17 and is only a "3.3 kW" (max output to the battery) and 3.8 kW max draw from the wall. It must run longer and therefore its fixed overhead (e.g. running pumps) is longer, so I wouldn't compare those numbers to yours.

Also, I have no idea where you are. You mentioned cold snap of -5 F. I suspect in warmer temps (say 75 to 85 F), the pack capacity will increase from where it is when it's cold and more energy will have come out of the "wall" given equal start (e.g. car run until dead) and end points (car stops charging when full).

'13 Leaf SV w/premium package (owned)
'13 Leaf SV w/QC + LED & premium packages (lease over, car returned)
'06 Prius

Please don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

ldallan
Posts: 32
Joined: Mon Jan 16, 2017 10:15 am
Delivery Date: 31 Dec 2016
Leaf Number: 000000

Re: Near Turtle to cells balanced: 20.8 kW with 2015 Leaf with 24 kW battery: Low kW? As expected? Battery losing capaci

Wed Feb 28, 2018 8:39 pm

Also, you didn't run the car low enough. If you wanted a more accurate measure, you should've run the car to below turtle, to when the contactor opens and the car won't move.


I'm hesitant to run the battery down to the point of "contactor opens" and then having to push the vehicle to where I can put some charge in it.

I was thinking that I could get to "Turtle mode" and then get home or to a nearby charging station. Then I'd run the heater + a/c until it reached "contactor opens" and the car was effectively "dead in the water". But ... I'd be right where I could plug in.

From that point, I could charge until "cells balanced" and see what the overall kW-hrs were added.

But ... I'm not really that curious and don't want to stress the battery by doing such a test. IIRC, there are some risks to shorting out a cell or three if you let the battery get too low.

Someone else willing to get to "contactor open" and they measure how much it takes to fully charge to "cell balancing"?

Levenkay
Posts: 495
Joined: Mon Sep 26, 2011 10:01 pm
Delivery Date: 11 Aug 2018
Leaf Number: 308382
Location: Portland, OR

Re: Near Turtle to cells balanced: 20.8 kW with 2015 Leaf with 24 kW battery: Low kW? As expected? Battery losing capaci

Wed Feb 28, 2018 10:58 pm

ldallan wrote:I'm hesitant to run the battery down to the point of "contactor opens" and then having to push the vehicle to where I can put some charge in it.


You could drive into your garage under Turtle, put the car in Park, and crank the climate control up with the windows open. Might take awhile to fully deplete the battery, but at least you'd know it was within reach of a charger when it shuts down.

cwerdna
Posts: 8396
Joined: Fri Jun 03, 2011 4:31 pm
Delivery Date: 28 Jul 2013
Location: SF Bay Area, CA

Re: Near Turtle to cells balanced: 20.8 kW with 2015 Leaf with 24 kW battery: Low kW? As expected? Battery losing capaci

Thu Mar 01, 2018 3:54 am

ldallan wrote:
Also, you didn't run the car low enough. If you wanted a more accurate measure, you should've run the car to below turtle, to when the contactor opens and the car won't move.


I'm hesitant to run the battery down to the point of "contactor opens" and then having to push the vehicle to where I can put some charge in it.

I was thinking that I could get to "Turtle mode" and then get home or to a nearby charging station. Then I'd run the heater + a/c until it reached "contactor opens" and the car was effectively "dead in the water". But ... I'd be right where I could plug in.

From that point, I could charge until "cells balanced" and see what the overall kW-hrs were added.

But ... I'm not really that curious and don't want to stress the battery by doing such a test. IIRC, there are some risks to shorting out a cell or three if you let the battery get too low.

I've never heard of the bolded part. The contactor opening should prevent further draining once the lowest cell reaches a critical voltage. Definitely don't leave the car in that state for too long (e.g. days) as you don't want self-discharge that happens over time to take it much lower. Just plug in immediately.

But yes, get it down to turtle or almost turtle then run the heater at full. viewtopic.php?p=149528#p149528 is what the famed Ingineer did.

'13 Leaf SV w/premium package (owned)
'13 Leaf SV w/QC + LED & premium packages (lease over, car returned)
'06 Prius

Please don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

powersurge
Posts: 1120
Joined: Wed Oct 21, 2015 10:24 am
Delivery Date: 06 Dec 2014
Location: Long Island, NY

Re: Near Turtle to cells balanced: 20.8 kW with 2015 Leaf with 24 kW battery: Low kW? As expected? Battery losing capaci

Thu Mar 01, 2018 7:13 am

I don't understand the fascination with how many KWH we can put into the battery, or other things after we reach turtle mode??

Quick version... don't run the car to turtle mode unless you need to drive to the hospital to save a life, or a T-Rex is chasing you. Otherwise, take care of your car and do experiments with cheaper items......

PS - You don't "balance" your battery cells by going down to 0% battery, no matter what anyone has told you.

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