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

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ldallan

Well-known member
Joined
Jan 16, 2017
Messages
52
Location
Colorado Springs, CO
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
 
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.
 
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.
 
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.
 
ldallan said:
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.
 
ldallan said:
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/2011/long-term-road-test/2011-nissan-leaf-driving-it-to-the-bitter-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).
 
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"?
 
ldallan said:
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.
 
ldallan said:
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. http://www.mynissanleaf.com/viewtopic.php?p=149528#p149528 is what the famed Ingineer did.
 
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.
 
I concur with the T-Rex chasing. Best to drive as far and as fast as u can in your Leaf, regardless of battery health and longevity. But, if their eyesight is based on movement, then...
 
cwerdna said:
But yes, get it down to turtle or almost turtle then run the heater at full. http://www.mynissanleaf.com/viewtopic.php?p=149528#p149528 is what the famed Ingineer did.

Thanks for the link. I figured my "work-around" of having the heat-on was "re-inventing the wheel". ;-)

Ingineer said:
I pulled into my garage and continued to move back and forth with CC still on high heat, and finally the car performed an auto Ig-off. (Battery Contactor Opened) It went into the same mode as you would with 2 power switch presses w/o the brake.

I'm unclear why he moved the car back and forth while in the garage. rather than just leaving in Park with the heat on full blast.

I suppose CC means "Climate Control"?

Regarding "cells shorting out", that may be obsolete information from vehicles with less sophisticated BMS (battery management systems).

In any case, I'm not inclined to go to "battery flat", especially without Leaf-Spy installed. (which I probably ought to obtain and get a compatible ELM-327)
 
Levenkay said:
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.

Agree with running the heater to drain the battery without the risk of having to push or tow the car to a charger.

My less-than-informed speculation is that running the heater might be the equivalent of driving at 10 mph or so. I have been curious about how much drain the heater puts on the battery. I've done relatively controlled tests on an 11 mile loop at speeds from 45 to 70 mph at about 15° F with the heater on and off, and it made a significant difference. But I didn't wrestle with the math to get more specific. Mea culpa?

The amount of battery drain from the heater while in PARK might be something Leaf-Spy could reveal.
 
powersurge said:
I don't understand the fascination with how many KWH we can put into the battery, or other things after we reach turtle mode??

I suppose it could be a matter of how much we want to Grok what is going on with our Leafs.

This time, I didn't intentionally drive until near "Turtle Mode", but since it happened, it seemed like a "why not" to measure how my kWH got put into the battery.

With the used Leaf being a lease-turn-in, and now that it has over 30,000 miles and still at 12-bars, I thought it might give me a hint on how far away it might be until 11-bars.

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......

I rarely drive until "Turtle Mode", but we can "agree to disagree" on just how bad of an idea it is to drive to the point of getting to "Turtle Mode". Are you recommending to have the Leaf towed if the Very Low Battery warning is reached (both GOM and Percent are blinking)? Unless it was a medical emergency or T-Rex?

I would describe my driving practices as "baby'ing the battery", but not that much. Certainly, I've never been in the situation of having the Leaf towed, or having to push it.

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

We are in "heated agreement" ... perhaps I was unclear for you to think that I was suggesting that "cell balancing" was related to getting the battery to ultra low or even to 0%. If so, my apologies.

FWIW:
My impression with laptops that may or may not extrapolate to the Leaf battery: it is "life in the real world" to have the laptop battery get to being completely drained. That seems to have the indirect benefit of helping the laptop system estimate battery life remaining, and maybe how long to full charge.

But we are probably also in "heated agreement" that there is a big difference between a $100 laptop battery that can be replaced, and a Leaf battery that might cost $5000 to $10,000 to replace. Ouch.
 
cwerdna said:
In Edmunds testing at https://www.edmunds.com/nissan/leaf/2011/long-term-road-test/2011-nissan-leaf-driving-it-to-the-bitter-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.

Thanks for the Link, and your interpretation.

That surprises me that there might be only 1 or 2 or 3 miles remaining after "Turtle Mode" reached, so I will be more careful in the future. I REALLY don't want to push the Leaf.

Also, there could be differences between the different model years, as you mention.

And if I stay in the mode of "Inquiring Minds Want to Know", I almost certainly should get Leaf-Spy and a compatible ELM-327.

OT? Thread-drift?
Am I the only one who is paranoid enough to worry about potential hacking with Leaf-Spy software that can apparently "Write" values to the car, such as windshield wipers, etc. I would prefer a less powerful Leaf-Spy that was "Read-Only".
 
ldallan said:
I'm pondering how to interpret that.
To summarize:
You don't know the charging efficiency;
You don't know the energy amount reserved, or the usable in the battery at the start of the charging.

But you think 20.8 kWh from the meter is a concern.
 
That surprises me that there might be only 1 or 2 or 3 miles remaining after "Turtle Mode" reached, so I will be more careful in the future. I REALLY don't want to push the Leaf.

Turtle mode is meant to give you enough time to park the car safely. It's the VLBW that should be taken as "I have just a few miles left." The goal for everyone should be to never see Turtle mode.
 
A question kinda related to this subject: I don't have a fancy EVSE, just the OEM, and do >90% of my charging on the dumb L2 at work. If I leave LeafSpy connected during charging (which I've never tried doing), will it measure the actual energy added to the battery, or is it always just estimating kWh from some other parameter?
 
ldallan said:
Am I the only one who is paranoid enough to worry about potential hacking with Leaf-Spy software that can apparently "Write" values to the car, such as windshield wipers, etc. I would prefer a less powerful Leaf-Spy that was "Read-Only".
That does seem kinda paranoid. Why would someone hack your phone then waste time dinking around with your car settings? Surely they could find something more valuable to play with?

I do worry about the future of car-hacking, but not until those infernal Skynet-spawned self-driving cars become common. It seems inevitable that they will not be secure enough to prevent some hostile actor from taking over a large number of cars and having them all suddenly turn sharply left into oncoming traffic (or the Jersey barrier) at the same time one morning.
 
finman100 said:
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.

I was just wondering about this myself. Looks like the most I've I've gotten into my 2015 SV from a ChargePoint station was 21.155kWh, but that was about a year ago. I'm pretty sure I was well past VLBW for that charge, but I've never taken it to Turtle. Still have all 12 bars.
 
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