Battery charging beyond 100% after strange activity earlier in the day

This morning as I pulled into my work's parking lot I had around 29% charge. I pulled in, put the car in park and turned the car off. After I turned it off there was an odd noise - almost sounded like someone trying to start their car but the battery wouldn't turn over, that type of noise. So after I heard the odd noise, I turned the car back on only to see that 29% charge suddenly dropped down to 24%. Fast forward to when I get home. I typically charge to 80%, but this time I wanted to charge to 100% just out of curiosity of what would happen. I come back later - well beyond the time that it should have taken to fully charge the vehicle - and I see that 1) there's a good amount of warmth coming from the front of the car and 2) that the 3rd blue light is still blinking. I unplug the charger, turn on the car and it's at 100% charge!? So not sure what's up with that. I leave the house to take the car for a spin to see if there'd be regen braking - and it regens to all of the "circles" except for the last one - if that makes sense. So even though it was fully charged - it was regenerating power... :-/ I drove it around long enough to drop the charge down to 73% - turned the 80% charge back on when I got home - charged it - and it stopped when it hit 80%. I'm not sure I even want to charge to 100% now - I feel like something is wrong. Anyone else run into this issue?? Last thing I need is a car that's on fire in my garage.

I have 240v charging at home by the way. Clippercreek HCS-50

kevmk81 said:

I turned the car back on only to see that 29% charge suddenly dropped down to 24%.

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This isn't that unusual... BMS estimates SOC two different ways. By open circuit voltage when the battery is disconnected, and by a much more complex and less accurate method while driving.

You didn't charge beyond 100%. Nissan doesn't let you access part of the battery at the top and bottom. 100% on the dash display isn't actually 100%. It's a bit less.

From your previous posts, it sounds like you have a '13, like me.

kevmk81 said:

I turned the car back on only to see that 29% charge suddenly dropped down to 24%. Fast forward to when I get home. I typically charge to 80%,

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Agreed with what WetEV said. Also, if you are usually not charging to full, that might help exacerbate inaccuracy.

kevmk81 said:

but this time I wanted to charge to 100% just out of curiosity of what would happen. I come back later - well beyond the time that it should have taken to fully charge the vehicle - and I see that 1) there's a good amount of warmth coming from the front of the car and

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Normal. This happens even if you don't charge to 100%. The on-board charger heats up and so does the inlet. Next time, charge for at least an hour and open the hood while charging. You'll feel the entire PDM stack is warm.

kevmk81 said:

2) that the 3rd blue light is still blinking. I unplug the charger, turn on the car and it's at 100% charge!?

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As for the bolded part, when the battery is closer to full (usually somewhere past 92% (I don't recall the exact numbers) on the dash display), the car will begin ramping down charge power and then do 3 bounces at the end. Not much energy makes it into the battery during that phase. It's not linear or steady state near the top, unlike when you charge to 80% where it's basically the same power level the whole time (w/a bit of variance) then car abruptly cuts power draw to 0. See http://www.mynissanleaf.com/viewtopic.php?p=490435#p490435. Your previous posts mention you have Leaf Spy. You can see how many battery gids it goes up to. And, you can see the charging power. You'll see it go down just like my ChargePoint graph.

As I've posted many times, if the dash display is at 98% or so, often, when you unplug, it'll "jump" to 100%, even though a bit more juice can be added to the battery.
http://www.mynissanleaf.com/viewtopic.php?p=423754#p423754
http://www.mynissanleaf.com/viewtopic.php?p=339977#p339977
http://www.mynissanleaf.com/viewtopic.php?p=446914#p446914

kevmk81 said:

So not sure what's up with that. I leave the house to take the car for a spin to see if there'd be regen braking - and it regens to all of the "circles" except for the last one - if that makes sense. S

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Not abnormal at all. If you charge to 100%, you'll have 0 available regen circles until you deplete the battery for a bit. At what SoC % on the dash you'll have all regen circles available varies, and can vary depending on battery temperature, condition and how full the battery was to start with. I suspect they just want to make sure there's no module that goes beyond some set critical high voltage and that's the limiting factor. For heavily degraded '11s and '12s, I hear there's very little regen. See examples below:
http://www.mynissanleaf.com/viewtopic.php?f=27&t=21961&p=462072&hilit=regen#p462072
http://www.mynissanleaf.com/viewtopic.php?f=31&t=20275&p=432849&hilit=regen#p432849
http://www.mynissanleaf.com/viewtopic.php?f=31&t=13371&p=459925&hilit=regen+kw#p459925
http://www.mynissanleaf.com/viewtopic.php?p=447931#p447931

You will NOT have a fire. '11 and '12 Leafs only could be charged to 80% via the timers. On model year US '14+ Leafs, they REMOVED the charge to 80% option. You have no choice but to charge to 100% or to terminate it early via either means (e.g. timer, unplugging early, EVSE with its own timer or that can be scheduled/remotely controlled). We have at least a dozen '14+ Leafs at my work who charge there. They go to full. I suspect many other pre-'14s are charged to full, as well.

When you do a charge to 100% is when the BMS balances the cells in the battery pack. This can take some time, depending on how often it is done. It does not charge the battery beyond 100%, but it extends the length of the charge cycle. You should do a 100% charge, at least once a month, and let it run until it finishes and shuts itself off.

Makes sense - thanks for the replies. Yes mine is a '13 SV

One thing I forgot to add - after the car made its' odd noises yesterday morning - the dash reset (as it has done so a few other times in the past) - so efficiency was reset - the car on and car off noises came back on - etc...

How often do other peoples leafs reset?

kevmk81 said:

Makes sense - thanks for the replies. Yes mine is a '13 SV

One thing I forgot to add - after the car made its' odd noises yesterday morning - the dash reset (as it has done so a few other times in the past) - so efficiency was reset - the car on and car off noises came back on - etc...

How often do other peoples leafs reset?

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Checked your 12V battery recently?

LEAFs doing odd things often mean a weak 12V battery.

kevmk81 said:

This morning as I pulled into my work's parking lot I had around 29% charge. I pulled in, put the car in park and turned the car off. After I turned it off there was an odd noise - almost sounded like someone trying to start their car but the battery wouldn't turn over, that type of noise. So after I heard the odd noise, I turned the car back on only to see that 29% charge suddenly dropped down to 24%. Fast forward to when I get home. I typically charge to 80%, but this time I wanted to charge to 100% just out of curiosity of what would happen. I come back later - well beyond the time that it should have taken to fully charge the vehicle - and I see that 1) there's a good amount of warmth coming from the front of the car and 2) that the 3rd blue light is still blinking. I unplug the charger, turn on the car and it's at 100% charge!? So not sure what's up with that. I leave the house to take the car for a spin to see if there'd be regen braking - and it regens to all of the "circles" except for the last one - if that makes sense. So even though it was fully charged - it was regenerating power... :-/ I drove it around long enough to drop the charge down to 73% - turned the 80% charge back on when I got home - charged it - and it stopped when it hit 80%. I'm not sure I even want to charge to 100% now - I feel like something is wrong. Anyone else run into this issue?? Last thing I need is a car that's on fire in my garage.

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Don't see really anything out of place here. You weren't by chance running LEAF Spy at the time?? Ahh... of course you wouldn't cause if you had, you wouldn't be posting this.

That clicking noise might indicate a boost of the 12 volt battery is in order. As the weather gets colder, edge case batteries start to fail. I would put it on a charger overnight at your earliest convenience.

You stopped the charge when it was in the balancing phase. This can last 2 hours but is not needed unless your trip will challenge the full range of the car. The other day (2018 with SOC meter) my LEAF was at 98% but LEAF Spy told me my charge was done. A "full" charge only goes to a real SOC of 97-98% on new battery.

I unplugged, rebooted and SOC meter immediately went to 100% although LEAF Spy verified no additional charge was added. In case you are curious, LEAF Spy registered a charging speed of .3 KW

Based on your observation that all regen was available but one circle suggests you were early in the balancing stage. It is the BMS desire to "top off" during the balancing stage that is a likely huge contributor to degradation. I would avoid it as much as conveniently possible.

Yep, 12 v is fully charged actually (have dealt with 12 v battery issues in the past and I've figured out what works for me)! I haven't used leaf spy lately tbh... i might start using that again

DaveinOlyWA said:

It is the BMS desire to "top off" during the balancing stage that is a likely huge contributor to degradation. I would avoid it as much as conveniently possible.

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This is the first time I've heard this. Can you elaborate a bit?

And how important is it to 'balance' the cells. If LeafSpy doesn't show a huge imbalance is there anything to be gained by letting the charger go until it stops? I rarely or never need more than about 40% of my full range in any single day so I could go indfefinately without a full charge. I haven't charged to full since the the cooler weather of the Spring and I'm wondering now if I need to do it at all...

goldbrick said:

DaveinOlyWA said:

It is the BMS desire to "top off" during the balancing stage that is a likely huge contributor to degradation. I would avoid it as much as conveniently possible.

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This is the first time I've heard this. Can you elaborate a bit?

And how important is it to 'balance' the cells. If LeafSpy doesn't show a huge imbalance is there anything to be gained by letting the charger go until it stops? I rarely or never need more than about 40% of my full range in any single day so I could go indfefinately without a full charge. I haven't charged to full since the the cooler weather of the Spring and I'm wondering now if I need to do it at all...

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First you heard of what? That its bad to charge to 100%? Because that "should" be well understood although it isn't because people choose to listen to a company that makes money selling new cars rather than making money ensuring older cars last longer.


FYI; cells balance 24 hours day, every day. The only reason for top end balancing is for more range which you by your statement is not going to be very helpful for you.

I was referring to the balancing being hard on the batteries, but I guess you meant that this occurs at very high SOC and that is the concern?

I've followed a lot of Li battery threads over the years but most of those were dealing with 18650 cells. I'm not sure how much that relates to the cells in a Leaf, but on the other hand, it's much easier to get a lot of data and folks have run numerous cells down until they failed in the interest of 'science' which is something a normal person can't do with a Leaf pack. My understanding is very low SOC and very high SOC and high temperatures accelerate degradation - pretty much the conventional wisdom on the care and feeding of Li cells. For the 18650 cells, it is also possible to permanently damage the cell if the SOC is low enough even once but I would bet the Leaf's BMS will not allow that to happen.

There may be some benefit to charging to 100% so the BMS know the voltage of the pack at 100% SOC but otherwise I tend to agree that there is not much benefit to doing this often. I guess I'll be the guinea pig and see what happens to my pack after a year of never reaching 100%. I'll report back next year

goldbrick said:

I was referring to the balancing being hard on the batteries, but I guess you meant that this occurs at very high SOC and that is the concern?

I've followed a lot of Li battery threads over the years but most of those were dealing with 18650 cells. I'm not sure how much that relates to the cells in a Leaf, but on the other hand, it's much easier to get a lot of data and folks have run numerous cells down until they failed in the interest of 'science' which is something a normal person can't do with a Leaf pack. My understanding is very low SOC and very high SOC and high temperatures accelerate degradation - pretty much the conventional wisdom on the care and feeding of Li cells. For the 18650 cells, it is also possible to permanently damage the cell if the SOC is low enough even once but I would bet the Leaf's BMS will not allow that to happen.

There may be some benefit to charging to 100% so the BMS know the voltage of the pack at 100% SOC but otherwise I tend to agree that there is not much benefit to doing this often. I guess I'll be the guinea pig and see what happens to my pack after a year of never reaching 100%. I'll report back next year

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I think you will find that you are unable to determine any effect of not charging to 100%. To save time, I have already done this. In 10 months, I have done very few full charges on my LEAF only electing to do so prior to long out of town trips, etc. For the day to day, I have more than enough range to cover what I need to do.

Another misstep by Nissan that you alluded to is the DoD (depth of discharge) The BMS is allowing too much of the battery to be used. No other EV manufacturer allows this. What they do allow can only be guessed at in most cases but its generally not 95% of total capacity of the pack.

I will admit to being one of the early detractors of the Volts' holding so much of its capacity back from being used. In retrospect, Nissan could have saved itself a lot of headache by adding a few kwh and doing the same.

goldbrick said:

I've followed a lot of Li battery threads over the years but most of those were dealing with 18650 cells. I'm not sure how much that relates to the cells in a Leaf, but on the other hand, it's much easier to get a lot of data and folks have run numerous cells down until they failed in the interest of 'science' which is something a normal person can't do with a Leaf pack. My understanding is very low SOC and very high SOC and high temperatures accelerate degradation - pretty much the conventional wisdom on the care and feeding of Li cells. For the 18650 cells, it is also possible to permanently damage the cell if the SOC is low enough even once but I would bet the Leaf's BMS will not allow that to happen.

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18650 refers to the form factor and says nothing about what's actually inside (e.g. chemistry, anode, cathode, etc.)

Per https://batteryuniversity.com/learn/article/battery_packaging_a_look_at_old_and_new_systems

A successful standard is the 18650 cylindrical cell. Developed in the early 1990s for lithium-ion, these cells are used in laptops, electric bicycles and even electric vehicles (Tesla). The first two digits of 18650 designate the diameter in millimeters; the next three digits are the length in tenths of millimeters. The 18650 cell is 18mm in diameter and 65.0mm in length.

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It would be like making sweeping generalizations about AA batteries which all have the same form factor. They could be carbon zinc, alkaline, NiCad, NiMH, etc. and even if you chose NiMH, there's a huge variation in how much capacity they can have, amount of self discharge over time, etc.

I know what 18650 means but I've never seen or heard of a 18650 cell that wasn't based on some form of Li chemistry. I suppose someone might make a 18650 alkaline cell or NiMH or whatever so I guess I should have clarified that I was referring to Li cells only.

And I agree that Li chemistry probably varies more than alkaline or NiMH (I don't really know that for a fact but Li tech appears to be changing quite rapidly). That is why I mentioned that I don't know how much the testing done on 18650 (Li) batteries applies to Leaf cells.

My only point is that the general consensus is that heat, and very low or high SOC are known to be bad for Li cells. The Leaf uses Li cells and even though they are not in the 18650 form factor I would guess the same applies to them.

cwerdna said:

when the battery is closer to full (usually somewhere past 92% (I don't recall the exact numbers) on the dash display), the car will begin ramping down charge power and then do 3 bounces at the end.

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Here's a picture of my L1 charging from last night. It's an eGauge "whole house" power monitor, so you need to ignore a few things:
- ignore the green stuff. That's just solar power production.
- fridge/freezer each added about 100 watts on-and-off all night. That's why the red line is bouncing all night.
- the furnace added 1kw off-and-on from 6:30 to 9:00am while it heated the house, then shut-off.
- Someone made coffee at 9:30am

...but even with all the noise, you can see the 600 watt ramp-down from 10am to 11:15am, then the "three bounces" cwerdina wrote of (about 1000 watts each). The car probably was reporting "99%" or "100%" SOC by 10am.

BTW, I've read on this forum that pack equalization does not happen with a 120v L1 charge. But I see this same power ramp-down at the end of my charges, whether they are 240v or 120v. [ EDIT: others have confirmed that the pack does equalize with L1 charging ]



It would probably be better to stop the charge before that last 10%, but it can be tricky to guess when that will happen when you are 120 volt charging. It's also getting chilly (45F), so I'm not too worried about a half day spent at 100%.

BTW, I've read on this forum that pack equalization does not happen with a 120v L1 charge.

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No, it does happen. What you've read is that it doesn't happen with an 80% charge on a car that has an 80% limit option. I thought it might, because the three charge lights will all stay solid right before it shuts off, but apparently not.

It would probably be better to stop the charge before that last 10%, but it can be tricky to guess when that will happen when you are 120 volt charging. It's also getting chilly (45F), so I'm not too worried about a half day spent at 100%.

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Using temperature as a charge guide is not a very good plan imho.

Charging should ONLY be based on need.

DaveinOlyWA said:

Using temperature as a charge guide is not a very good plan imho.

Charging should ONLY be based on need.

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I meant that I try to limit charge to 80% when it's hot and the car drives farther; and I don't worry too much if I hit 100% when it's freezing out and I need more range anyways.

Charging to 80% in summer and 100% in winter seemed like a good compromise, because it gives most of the benefits of "80% charging," yet also gives me roughly the same driving distance all year (win/win). It's the old "80/20" rule: 80% of the benefit with 20% of the inconvenience.

I meant that I try to limit charge to 80% when it's hot and the car drives farther; and I don't worry too much if I hit 100% when it's freezing out and I need more range anyways.

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That's fine.