12% capacity loss in 9 months is "normal"

[tbleakne]

GIDs might be 80 Wh into the battery, but you do not recover
the full 80 FROM the battery.
Since we drive with the recovered energy, not what was put in,
the "usable" 75 Wh per GID accounts for that loss.

Supposedly GIDs are WHAT IS STORED in the battery, it took a bit more than that to fill those batteries but we dont care about that.. extracting those kWh out of the battery wont be 100 percent efficient, especially if you drive aggressively.. but 75 sounds like a reasonable number with motor/inverter, tires and gearing losses. The battery itself will be close to 100% efficient while discharging, otherwise it would get very hot.

I doubt it.

Just by watching the battery temperature bars while driving, I'd expect the discharge efficiency will be found to be somewhere in the mid 90's percent, once it is accurately calculated. Both the 80/75 gid count and Carwings available battery capacity reports, as compared to Phil's calculations of total battery capacity, point to this eventual conclusion.

95% discharge efficiency would mean about 1 kWh was released as heat over a full LEAF battery pack discharge cycle.

The battery does not get "very hot", since that's not very much heat, given the thermal mass of a 600 lb battery pack, which is constantly being passively cooled, while you drive.

A better way to measure the efficiency of the battery discharge, separate from the losses in the inverter/motor, is to monitor the battery voltage drop under load with the gid meter.

Data collection procedure:
record idle voltage with car at rest or in neutral.
operate car at uniform power level, 10, 20, 30, 40 kW
record voltage at each power level
return car to stop or neutral, and record idle voltage again.

Since I do not have the data-logger port (nor a lap-top to connect it to), it is difficult for me to get precise readings while driving, but here are my rough results:

Power Voltage Drop
10kW 4V
20kW 5-6V
30kW 8-11V
40kW 13-15V

(voltage drop)/(idle voltage) = the fraction of power lost in battery discharge.
The pack voltage was about 375 volts, so under most cruising conditions, where power is no more than 30 kW, battery discharge loss is no more than 3%.

 

[surfingslovak]

Just by watching the battery temperature bars while driving, I'd expect the discharge efficiency will be found to be somewhere in the mid 90's percent, once it is accurately calculated. Both the 80/75 gid count and Carwings available battery capacity reports, as compared to Phil's calculations of total battery capacity, point to this eventual conclusion.

95% discharge efficiency would mean about 1 kWh was released as heat over a full LEAF battery pack discharge cycle.

The battery does not get "very hot", since that's not very much heat, given the thermal mass of a 600 lb battery pack, which is constantly being passively cooled, while you drive.

A better way to measure the efficiency of the battery discharge, separate from the losses in the inverter/motor, is to monitor the battery voltage drop under load with the gid meter.

Data collection procedure:
record idle voltage with car at rest or in neutral.
operate car at uniform power level, 10, 20, 30, 40 kW
record voltage at each power level
return car to stop or neutral, and record idle voltage again.

Since I do not have the data-logger port (nor a lap-top to connect it to), it is difficult for me to get precise readings while driving, but here are my rough results:

Power Voltage Drop
10kW 4V
20kW 5-6V
30kW 8-11V
40kW 13-15V

(voltage drop)/(idle voltage) = the fraction of power lost in battery discharge.
The pack voltage was about 375 volts, so under most cruising conditions, where power is no more than 30 kW, battery discharge loss is no more than 3%.

Yes, agreed. I have collected some anecdotal data a while ago, and internal resistance appears to be low. Around 50 mOhm, possibly less, for the entire pack. The trouble with this is that the internal resistance curve is nonlinear, it roughly resembles a bathtub and depends on SOC level.

Be that as it may, Gary pointed out something interesting a while ago. We lose energy on the way in, during charging, and on the way out, during vehicle operation. I believe that Nissan said that the battery gets hotter on a level 2 charger, and remains a bit cooler when driving. If you assumed symmetrical losses for the sake of simplicity, you would only need to lose 2.5% each way, on average, to get 95% roundtrip efficiency.

To put it in other words, you would lose about 500 Wh during a full charge, which is roughly like using a 100W bulb to warm the pack for a few hours. Not a very scientific comparison, but perhaps a plausible one. What do you think?

 

[Herm]

AFAIK Gids are derived from a Coulomb count of what went into the battery, and they don't reflect the amount of energy the battery is physically holding perfectly accurately. It can only be an estimate, a close guess, but still an estimate.

IIRC GIDs are derived from a coulomb count of what is going out subtracted from an initial model, occasionally recalibrated by measuring the resting voltage, but it could easily be as you describe.

 

[tzzhc4]

Just to add some data to the discussion, my LEAF #889 was delivered March 30, 2011, almost 12 months ago. It has 11,049 miles at this moment. I have had one of Gary's SOC meters for months, since September IIRC. I charge to 100% routinely and I have logged gids upon first drive each day and at end of day for months. I've been getting 281 gids repeatedly, in fact 6 times out of 13 full charges that I have documented in March were to 281 gids, and 5 more charges were no lower than 278 gids. So I think that I have full capacity at the same total mileage as Tick Tock, and I'm ignoring Nissan's "long life" recommended charging schedule of 80% charging.

To add my data my LEAF, #2192 was delivered June 2nd 2011, right around 12 months ago and has just over 11k miles on it. I had been only charging to 80% until I noticed recently the car was only charging to 75% with Carwings. I confirmed this with my GID SOC meter (which showed 74% 208 gids). I have tried charging to 100% several times after this and the latest "100%" charge is only 247 gids and so far no higher than 250 gids

I took my car in for the "yearly" battery check today so it will be interesting to see what it comes back with. Will pursue Nissan after this and contienue documenting my loss.

 

[mwalsh]

I took my car in for the "yearly" battery check today so it will be interesting to see what it comes back with. Will pursue Nissan after this and continue documenting my loss.

Yes, that would be MOST interesting. I was thinking I might take mine in and get an extra battery check. I have the advantage of my dealer being base-camp for the Nissan engineering team, so we get their top man working on our cars (unless he's checking on odd-ball issues elsewhere).

Incidentally, my car has been charged a total of 363 times in the last 17 months. Or at least that's what I have saved email notifications for. 299 of those were full charges; 36 were to "10 of 12 bars", so presumably to 80%; 10 were to "11 of 12 bars" (maybe failed full charges?); and 18 were "other" (between 3 and 9 bars worth).

 

[surfingslovak]

To add my data my LEAF, #2192 was delivered June 2nd 2011, right around 12 months ago and has just over 11k miles on it. I had been only charging to 80% until I noticed recently the car was only charging to 75% with Carwings. I confirmed this with my GID SOC meter (which showed 74% 208 gids). I have tried charging to 100% several times after this and the latest "100%" charge is only 247 gids and so far no higher than 250 gids

Thank you for sharing this! I sincerely hope that eventually there will be a satisfactory resolution to all of this. Perhaps we simply don't understand the car as well as we think we do. That said, my Leaf has nearly identical parameters to yours, and had 279 Gids on a full charge last time I measured. A friend of mine has been driving it for the past 2 1/2 months, and he has been charging to 100% more often than I would like. I will run a few tests this weekend, and let you know what the outcome was. I will start a Google doc tracking my capacity numbers as well.

 

[tzzhc4]

Yes, that would be MOST interesting. I was thinking I might take mine in and get an extra battery check. I have the advantage of my dealer being base-camp for the Nissan engineering team, so we get their top man working on our cars (unless he's checking on odd-ball issues elsewhere)..

Wow, wish we had that here. I went to pick up my car and the sheet they gave me just said they rotated the tires so I went and spoke to the service manager at Nissan of McKinney and was told the battery check was included in the 11 point inspection. I mentioned that isn't the case and this is the 12 month battery check and there is supposed to be a print out that rates the battery and how I charge and such. He tried to tell me that isn't the case and was fairly condescending. So it sounds like they did not run the battery check. I called the Nissan hotline and explained the situation, they said there should have been a printout along with few other maintenance items and they will call the dealership and see what was done in the mean time I am going to take my LEAF to another dealership tomorrow to get the 12 month battery check.

 

[EdmondLeaf]

I went to pick up my car and the sheet they gave me just said they rotated the tires so I went and spoke to the service manager at Nissan of McKinney and was told the battery check was included in the 11 point inspection. I mentioned that isn't the case and this is the 12 month battery check and there is supposed to be a print out that rates the battery and how I charge and such. He tried to tell me that isn't the case and was fairly condescending. So it sounds like they did not run the battery check. I called the Nissan hotline and explained the situation, they said there should have been a printout along with few other maintenance items and they will call the dealership and see what was done in the mean time I am going to take my LEAF to another dealership tomorrow to get the 12 month battery check.

Not sure if I should laugh or cry. They told me they sold 26 Leaf, maybe a good reason and time to learn something/anything about them. Are we really on our own in this, seriously?

I called the Nissan hotline and explained the situation, they said there should have been a printout along with few other maintenance items and they will call the dealership and see what was done in the mean time I am going to take my LEAF to another dealership tomorrow to get the 12 month battery check.

Wonder if is not better for you to wait few days and collect data to see how this are going for you

 

[tzzhc4]

Not sure if I should laugh or cry. They told me they sold 26 Leaf, maybe a good reason and time to learn something/anything about them. Are we really on our own in this, seriously?

Hahaha, makes you wonder. My wife reminded me she had issues with them years ago when she brought her Frontier in for some warranty issue. Suffice to say I am glad I did not buy my LEAF there. Only took the LEAF there today because it was the closest dealership.

Wonder if is not better for you to wait few days and collect data to see how this are going for you

It is due for the 12 month battery check, been getting emails from the LEAF service reminder. So just trying to get it in. I will be surprised if anything comes of it but we will see.

Thank you for sharing this! I sincerely hope that eventually there will be a satisfactory resolution to all of this. Perhaps we simply don't understand the car as well as we think we do.

I really hope so because other than this capacity issue my wife and I really like the LEAF and the whole concept and frankly our experience with Nissan vehicles over the years.

 

[LEAFfan]

I talked to one of the ECO techs today while QCing, and you owners in Phoenix aren't going to be too happy about what he told me. He talked to someone that had tested these packs, and was told that in AZ, they are expected to lose a capacity bar every 15,000 miles. So that would be only about 78% left in just two years. Even his LEAF lost one recently and then a few minutes later it came back. He tested his pack after an L2 100% charge, and he said he only has 17.6kW h capacity left. He also said he drove a LEAF in TN and tested that one after a 100% L2 charge and it said there was 23.6kW h in that pack available.

 

[planet4ever]

He also said he drove a LEAF in TN and tested that one after a 100% L2 charge and it said there was 23.6kW h in that pack available.

Available? Sorry, I refuse to believe that one. Are you pulling our leg? Trying to do a one-up on evnow?

Ray

 

[DaveEV]

He also said he drove a LEAF in TN and tested that one after a 100% L2 charge and it said there was 23.6kW h in that pack available.

Available?

The number is probably the BMS estimate of total capacity. If capacity is 23.6 kWh, that's 295 GIDs. A "100%" charge is 95% capacity which is 280 GIDs. So the tech was probably looking at a normal car.

If his car only has 17.6 kWh capacity, that would suggest that a "100%" charge is getting him around 210 GIDs. But that should mean that he has lost 3 battery capacity bars, not just one, so something is definitely fishy here.

 

[Herm]

Incidentally, my car has been charged a total of 363 times in the last 17 months. Or at least that's what I have saved email notifications for. 299 of those were full charges; 36 were to "10 of 12 bars", so presumably to 80%; 10 were to "11 of 12 bars" (maybe failed full charges?); and 18 were "other" (between 3 and 9 bars worth).

How low is the battery when you recharge it, usually?
I believe battery life is 1000-1500 full cycles to 70% end of life degradation.

 

[mwalsh]

How low is the battery when you recharge it, usually?
I believe battery life is 1000-1500 full cycles to 70% end of life degradation.

25-30% charge remaining.

 

[Herm]

25-30% charge remaining.

at your rate you will reach 1000 cycles in about 6 years.

 

[mwalsh]

at your rate you will reach 1000 cycles in about 6 years.

Which is more or less what I was expecting. Actually I figured after 5 years I would be needing to charge to 100% overnight to get to the office, but also to charge some (probably all day on L1 would be more than sufficient) to have adequate charge for the trip home.

Of course I was hoping that a pack rebuild would only be around $5k by then too!

 

[TickTock]

Yup, this was my expectation, too. With the further hope of pack expanders being available (after-market if not by Nissan). However, I'm not giving up yet. All will be fine if the promised "leveling off" of degradation occurs. If not, and we continue to see 20% degradation each year, I have no doubt Nissan will do the right thing.

 

[DaveinOlyWA]

ya know, one thing i factored into my purchase decision was the increased public charging options. in 5 years, i expect i will have a lot more options to charge. i might be wrong.

i also figured on being able to cope with a 50 mile range. that would obviously prevent me from leaving town unless the charging network is much more developed by then and things "seems" to have gone slowly but in retrospect; i am simply wanting more than anyone can really provide.

to me; public charging options is like Crack. there more i see popping up, the more i want. before i was happy to have a few on my end of town. now, i complain because there is not something at least every 4-5 blocks apart. that is human nature. i get used to a level of service and that only makes me want something better.

L2's every 2 miles was yesterday's service. where is "today's" level of service?!!

i guess i will probably never be happy. i can see it now, in 2020. i will be complaining because it takes me 10 minutes to charge up while the few remaining gas cars can fuel up in less than 5 minutes at the 100% automated "never a line" gas stations!

 

[mwalsh]

If not, and we continue to see 20% degradation each year, I have no doubt Nissan will do the right thing.

I just want to reiterate that I only have 7-8% loss for the 17 month period. What is bothering me most right now is that 5-6% of that loss occurred quite slowly over 16 of those months, but the other 2-3% has occurred over just 6 weeks.

 

[thankyouOB]

if you dont have a gidmeter, how can you measuring the percentage loss?

mike, I assume you are using some measuring tool. what is it?
and you also had a baseline measure when you bought?