Capacity Loss on 2011-2012 LEAFs

[Valdemar]

We've seen everyone lose the 4th bar in a range of 42-43.5Ah Wouldn't it unrealistic to think Nissan is playing God on these and remotely triggering these events?

You've nailed it, no one else but Carlos Ghosn personally pushes a big red button with number "4" engraved on it every night before he goes to bed and a computer program written by offshore contractors in Bangalore picks a winner randomly from a pool of VIN numbers that are currently reporting 42-43.5Ah.

If seriously, the variance is likely due to some logic (or flaw) in the algorithm that the LBC uses to determine the bar count. For example, the LBC may store the capacity value it discovered initially when the pack was new and calculate % lost using the current Ahr measurement relative to that number. There is likely some variance in capacity across different packs when they are new, so while the % when the 4th bar drops across cars is the same the Ahr number when it happens is different.

 

[hillzofvalp]

Or telematics is checking the value against the entire leaf fleet data set and adjusting trigger points based on how other cars have performed or based on geographic location.

If more cars aren't being used as much, like in the winter or due to other connectivity problems, the data isn't uploaded as often and en masse and therefore no cars receive instructions to drop a bar. ??

There are other ways telematics can be a factor and not just be someone reviewing data every month and allowing a certain amount of replacements per month based on corporate budget

 

[hillzofvalp]

What are all of the things that can be reset or would likely to be reset or zeroed? For example, if I unplug the 12V battery, the temperature will zero at the actual temperature (instead of climbing up and up based on averaging temperatures when traveling over 16mph).

It seems to me that the bars are always lost when the bms "recalibrates" (hops upward in its estimate). I've heard a lot of people say that shortly after the bar drops, Hx and SOH hop back up to 66%.

What I need to understand is how the algorithm decides when to hop back up, basically when it is beginning to believe it has too much negative error. I have seen this happen where I was at 44.2 and the next day jump to 44.78. Ever since then it has been stuck at 44.44 and seems like it's not getting the data it needs to make a new report.

If no one has lost a bar just from the car sitting there (aka woke up and the bar was gone in the garage) then this means that this value is only updated when the car is above 16mph just like the temperature. If this is the case, then unplugging and reconnecting the 12V battery might cause it to refresh, like I was able to do by forcing a set temperature via a 1.5K resistor across the exterior thermistor followed by rebooting the 12V system. If you unplug the thermistor it goes down to -22F and the only way to get it back up aside from reboot is to drive like 30 miles

I think the car might be passing speed info to the bms and doing bar loss calculations all on the pack side. If this is the case we got to think harder.

Is there anything powered by 12V even after you disconnect the battery? Maybe residual capacitance keeps some micros active for a while?

 

[TimLee]

... It seems to me that the bars are always lost when the bms "recalibrates" (hops upward in its estimate). I've heard a lot of people say that shortly after the bar drops, Hx and SOH hop back up to 66%.

What I need to understand is how the algorithm decides when to hop back up ...

If no one has lost a bar just from the car sitting there (aka woke up and the bar was gone in the garage) then this means that this value is only updated when the car is above 16mph just like the temperature. ...

Very unlikely telematics has anything to do with it.

The LEAF appears to recalibrate both status of charge and SOH and AHr and probably capacity bars when put into Ready after having been OFF.

The only time it can really know battery status is initial power up when there isn't a load on the pack.

Now it may also require some amount of power use on the previous operating cycle and/or some charging of the pack.

I don't think 16 mph speed has anything to do with it.
I don't think ambient temp update requires 16 mph speed either.
I have seen it update without the LEAF moving.

 

[hillzofvalp]

It has been confirmed. It won't increase without being over 16mph. It will decrease at any time though. From an engineering point of view I can see why they do that so that the engine bay heat doesn't appear as actual outside ambient temp when you come to a stop.

If you have seen it update without leaf moving and it was in ready mode, then it must have to do with how much capacity is drained above a certain c rate.

 

[kolmstead]

Hill, you're fighting a tough battle. The Leaf's BMS in some fashion inhibits capacity bar loss during cold months. Almost nobody reports a bar loss during winter months. As my battery pack cooled down last fall/winter, it reported a gain of about 0.5 Ahr. I'm sure this wasn't real, just a fudge factor that Nissan uses to prevent thousands of Leafs from losing a bar when winter hits. Now that my battery temp is rising, reported capacity is dropping again. I have no doubt that my car will lose the ninth bar in March, just as it lost the tenth last year.

I suspect that I could have forced the bar loss if I had a way to keep the battery warm for a week or two, but that just wasn't possible. So the car went over 60 months w/o qualifying for a new battery. I saw capacities as low as 42.17 Ahr, but then the weather turned cold and my hopes faded. Everything I tried (driving hard, leaving discharged or charged to 100%) either had no effect or actually improved the reported capacity.

If you're up against the mileage limit instead of time, you can try parking the car. Charge/discharge cycles will have little or no effect unless they get the battery HOT and keep it that way.

-Karl

 

[hillzofvalp]

I have the battery at about 80-95F as I've heated my garage. I still haven't seen Hx, Ah, or SOH change at all. It's been over a couple months since I last saw it change.

In the hidden menu I changed the date a few months ahead, but I don't know what the official system date is that the algorithm would use. Perhaps there is a separate clock set by the telematics or NIssan only.

 

[hillzofvalp]

Hill, you're fighting a tough battle...

-Karl

I'm fighting Nissan's stupid strategies and poor corporate ethics.

 

[Lambtron]

Hill, you're fighting a tough battle. The Leaf's BMS in some fashion inhibits capacity bar loss during cold months. Almost nobody reports a bar loss during winter months. As my battery pack cooled down last fall/winter, it reported a gain of about 0.5 Ahr. I'm sure this wasn't real, just a fudge factor that Nissan uses to prevent thousands of Leafs from losing a bar when winter hits. Now that my battery temp is rising, reported capacity is dropping again. I have no doubt that my car will lose the ninth bar in March, just as it lost the tenth last year.

I suspect that I could have forced the bar loss if I had a way to keep the battery warm for a week or two, but that just wasn't possible. So the car went over 60 months w/o qualifying for a new battery. I saw capacities as low as 42.17 Ahr, but then the weather turned cold and my hopes faded. Everything I tried (driving hard, leaving discharged or charged to 100%) either had no effect or actually improved the reported capacity.

If you're up against the mileage limit instead of time, you can try parking the car. Charge/discharge cycles will have little or no effect unless they get the battery HOT and keep it that way.

-Karl

I lost my 3rd bar last month (January)in a 40* garage sometime during the night. It was missing at startup.

Lost third bar 01/13/16. 26495 mi.
198 gids
95.6% soc (100%)
46.35 AHr
16 kWh
70% SOH
49.91% Hx
393.4 V

 

[TimLee]

I have the battery at about 80-95F as I've heated my garage. I still haven't seen Hx, Ah, or SOH change at all. It's been over a couple months since I last saw it change.
...

It must not be seeing operation cycles.

They may have based that on some combination of power discharge or miles.
Something that you cannot make happen with it sitting in the garage.

Not likely it has anything to do with calendar date or telematics.

With recent cold in TN, my pre-3227 2011 that is missing three capacity bars now has SOH of 74% and is close to 49 AH capacity.
I feel your pain.
I hit five years on May 17.
Unlikely I win the infamous Nissan battery lottery.

 

[mwalsh]

You have to work it, and you apparently need to time it right. Driving as you normally do and keeping your fingers crossed does not appear to be a winning formula, and left too late one that will leave you out of options on either time or mileage. Or both.

In the case of my own car, which I was fairly certain wouldn't make it if I just left it to chance over the winter, I had to drive to nowhere almost every day in the final 6-8 weeks before our summery weather departed for good, and drive hard too. The scheme being fairly simple - get the pack temps up and keep them there by normal means; strain the pack as much as possible without beaching the spirit of the warranty agreement; and make it so I needed a full recharge each and every day (sometimes multiple times daily) from as low in the pack as I dare run without being near an EVSE.

Of course I can't guarantee success for you in following my suggestions, but I can say that it worked for me, and I only needed to put in a bit of extra time (which I probably would have spent equally trying to game the system in other ways anyhow).

 

[pchilds]

I don't understand why people wait until the last 1000 miles to try and drop the last bar. You need to be proactive, the warranty is designed for you to fail. There is nothing wrong with doing everything you can to get a new battery. Start early and remember you need the summer heat. Don't come here in February with 59000 miles and 2 weeks to go, it isn't going to drop.

 

[mwalsh]

I don't understand why people wait until the last 1000 miles to try and drop the last bar. You need to be proactive, the warranty is designed for you to fail. There is nothing wrong with doing everything you can to get a new battery. Start early and remember you need the summer heat. Don't come here in February with 59000 miles and 2 weeks to go, it isn't going to drop.

With the same set of circumstances you may be in better shape in July or August though. Which is one of our continuing problems - we truly don't know what the final contributing factor for bar loss is. Once we get that sorted (if we ever do) I think we'll be in better shape for advising people on a proper course of action. Until then we're really just shotguning ideas.

 

[hillzofvalp]

I don't seriously need my car until Spring, so I'm going to just let it sit there for a couple more months on the charger. Once I get insurance back on it in spring I'm going to haul ass to the dealership... and QC along the way. If it drops.. there will be a party with a big cake delivered to the dealer... with special icing.

 

[Levenkay]

I don't seriously need my car until Spring, so I'm going to just let it sit there for a couple more months on the charger. Once I get insurance back on it in spring I'm going to haul ass to the dealership... and QC along the way. If it drops.. there will be a party with a big cake delivered to the dealer... with special icing.

I haven't any personal experience with this, but from what I gather on this group, leaving the car plugged in for a long time is a certain recipe for wrecking the 12V accessory battery and thereby rendering the LEAF inoperative. If you want the "haul ass to the dealership" part of your plan to work, I think you should either connect a supplimental "battery tender" to the 12V battery, or disconnect the LEAF's charging cable. If you're trying to intentionally accelerate the wearout of your LEAF's traction battery, that purpose is served by simply having the battery sit at 100% charge, whether the charging cable is connected or not. So, turn off the timers, let the thing fully charge, unplug it, and then only reconnect it for an hour or so every couple weeks.

 

[hillzofvalp]

Nissan keeps recommending that I damage the battery intentionally from all the phone calls I've had with them. No guilt would be felt.

I've noticed that it tends to drop down to 85-90% within a day of hitting 95% if I leave it plugged in. Maybe that's because it's so out of balance. 25-40mV on the upper end.

 

[Stanton]

I don't understand why people wait until the last 1000 miles to try and drop the last bar. You need to be proactive, the warranty is designed for you to fail. There is nothing wrong with doing everything you can to get a new battery. Start early and remember you need the summer heat. Don't come here in February with 59000 miles and 2 weeks to go, it isn't going to drop.

You hit the nail on the head: it took me ~6 months (and several thousand miles) of hard driving in the Texas heat to finally drop my 4th bar (and that was just as temps were cooling off). 100% charges/highway driving/hitting VLBW...and all in the heat of the day. Now I'm back to 80% charges early in the morning and almost never even hitting LBW (of course that's much easier when you have a new battery).

 

[Lambtron]

I seems to me that by driving in "ECO" with the extra Regen Braking might heat the battery faster. Or is the difference negligible?

 

[Stanton]

I seems to me that by driving in "ECO" with the extra Regen Braking might heat the battery faster. Or is the difference negligible?

Even if it did, there's one problem: Regen pretty much goes away once you have a sufficiently degraded battery.
You pretty much need a hot environment (e.g. outside temps) to do the trick.

 

[fooljoe]

I seems to me that by driving in "ECO" with the extra Regen Braking might heat the battery faster. Or is the difference negligible?

Yes, sustained high regen will heat the battery, but whether you achieve this through using ECO mode with your foot off the accelerator or just hitting the brake pedal in "D" mode doesn't make a difference. And sustained high acceleration will do the job as well, or a better job since you can accelerate at a higher kW than you can regen.

Also, it's amperage that heats things up, and you need more amps to achieve the same kW when you're at a low SOC than a high SOC, plus full regen isn't available until your SOC is fairly low anyway. So in short, I by no means recommend this (especially on public roads), but alternating between high acceleration and high regen while at a low SOC will certainly heat up your battery. AKA "spirited driving".