Evidence of bad battery cell?

[occ]

I'd like to get some mnl expert advice here.

Recently, I noticed that my third fuel bar disappeared very quickly. In the summer, I use to see about 5.5 to 6 miles before any bars disappeared. Now on my latest drive (yesterday), my third bar disappeared in about 2 miles!

/bar Running
1st bar ~ 4.5 4.5
2nd bar ~ 5 9.5
3rd bar ~ 2 11 !!
..
4th bar ~ 5 I think...I stop noticing

This was yesterday's run:

full lvl2 charge
total 67 miles (7 miles stop/go; 60 miles freeway, 45 of those miles at 60-65mph, 15 of those at 55mph - was getting range anxious)
1 mile into "very low bat warning" at end of trip
dash avg 4.5 mi/kwh (reset when this 67 miles trip started)
55degF (dash temp)
There were 2 off/on during the trip (stopped twice from full charge). This was early in the run.
absolutely no climate control - I knew I was stretching range that night.


I did wish I had the GID meter yesterday.

I started noticing 3rd bar's anomaly for about 2 months now...I had thought it was normal and that it would go away once the car does its battery balancing cycle. BTW, my charge timer is mixed, 3 days to 80%, 4 days to 100% every week for year and a half now.

I did have the update in June'12 when I went in for my 1yr battery check. But I'm pretty sure I had normal 5-6miles/bar since then until recently. I know that not all the bars are even, but the third bar seems way off (I thought there was a thread about this, but can't seem to find it).

Anyways, any insight would be appreciated!


(edit: oops..sorry, sorry I meant to put this in general discussion..how to move it?)
(edit: added line about no climate control)

 

[FairwoodRed]

I recently found that my bars were going away much earlier in my commute. I was reaching my first stop just into my fourth bar rather than just into my third bar. It essentially changed overnight. Such an abrupt change led me to think I had a cell that failed, so I took it to my friendly dealer, Nissan of the Eastside. They checked out my pack and said it was healthy as a horse when they looked at cell pair voltages.

But we’re not the first ones to notice this. While at the dealer I ran into TaylorSFguy who was also getting a cell pair voltage test (I think his worst cell was 17mV off at 66,000 miles) He describes something similar. He notices that his third and fourth bars have much less range than the others. I think he first noticed that last spring.

This probably isn’t a serious issue, and could even be normal. We won’t know unless more people develop the symptoms.

 

[garygid]

When you power the car on, if you see a bar, it "should" be
at least half full. However, as the car's battery pack looses
capacity, the bars would normally loose capacity too.

Then, depending mostly upon temperature, the car might
mess with the bars in ways that are unexpected, or unknown.

 

[mwalsh]

I'd like to get some mnl expert advice here.

Recently, I noticed that my third fuel bar disappeared very quickly. In the summer, I use to see about 5.5 to 6 miles before any bars disappeared. Now on my latest drive (yesterday), my third bar disappeared in about 2 miles!

/bar Running
1st bar ~ 4.5 4.5
2nd bar ~ 5 9.5
3rd bar ~ 2 11 !!
..
4th bar ~ 5 I think...I stop noticing

This was yesterday's run:

full lvl2 charge
total 67 miles (7 miles stop/go; 60 miles freeway, 45 of those miles at 60-65mph, 15 of those at 55mph - was getting range anxious)
1 mile into "very low bat warning" at end of trip
dash avg 4.5 mi/kwh (reset when this 67 miles trip started)
55degF (dash temp)
There were 2 off/on during the trip (stopped twice from full charge). This was early in the run.

I did wish I had the GID meter yesterday.

I started noticing 3rd bar's anomaly for about 2 months now...I had thought it was normal and that it would go away once the car does its battery balancing cycle. BTW, my charge timer is mixed, 3 days to 80%, 4 days to 100% every week for year and a half now.

I did have the update in June'12 when I went in for my 1yr battery check. But I'm pretty sure I had normal 5-6miles/bar since then until recently. I know that not all the bars are even, but the third bar seems way off (I thought there was a thread about this, but can't seem to find it).

Anyways, any insight would be appreciated!


(edit: oops..sorry, sorry I meant to put this in general discussion..how to move it?)

My car behaves much like yours does sometimes. And I stress sometimes, because it didn't today. Today was a pretty steady 65mph run over the 30.5 miles into work and I worked all the voodoo I could to maximize charging (10 minute bump 2 hours after full charging had completed and 30 minutes of cabin pre-conditioning). Lost bar one at 5 miles (would normally expect 4.5 miles at best); bar two at 11.5 miles; bar three at 15 miles; and bar four at 20 miles.

Before I had the software update, bar one was the really unpredictable bar. So I've generally always averaged over the first four bars, looking for a (post software update) return of between 4.5 and 5 miles per bar @ ~65mph. Today I just happened to nail it!

I would really suggest a Gidometer. It's especially useful when you're down below that point where you're no longer seeing DTE in miles on the Guessometer.

At 67 miles I would expect to have between 7 and 10 miles remaining. I would have around 13 miles remaining when I hit LBW, and would probably hit LBW at ~64 miles the way I'm driving now (with around 4.6-4.7 miles/kWh efficiency). Using CC instead of my delicate size 10s would sap about 3 miles from that, bringing me to LBW at around 61 miles.

Verified pack degradation in my car is 11%.

 

[RegGuheert]

Such an abrupt change led me to think I had a cell that failed, so I took it to my friendly dealer, Nissan of the Eastside. They checked out my pack and said it was healthy as a horse when they looked at cell pair voltages.

But we’re not the first ones to notice this. While at the dealer I ran into TaylorSFguy who was also getting a cell pair voltage test (I think his worst cell was 17mV off at 66,000 miles) He describes something similar.

I'm convinced that most dealers do the cell voltage testing at a much higher SOC than they should. Measuring the cell pair voltages at a high SOC is pretty worthless since this battery pack is top balanced. Unless they gave you the voltage of the cells along with the differences, there is no way to know that they did it correctly.

 

[reeler]

Will we ever know if a cell or pack has gone bad? I am not worried about degradation, but what if a cell needs replacing. Would we ever know by going to the dealership for our annual checkup?

I bet that information could be read from the car's computer if someone could decode the messages.

 

[RegGuheert]

Recently, I noticed that my third fuel bar disappeared very quickly. In the summer, I use to see about 5.5 to 6 miles before any bars disappeared. Now on my latest drive (yesterday), my third bar disappeared in about 2 miles!

/bar Running
1st bar ~ 4.5 4.5
2nd bar ~ 5 9.5
3rd bar ~ 2 11 !!
..
4th bar ~ 5 I think...I stop noticing

I often lose the 3rd (really 10th) bar after only about 1.5 miles, but that is because I'm climbing a steep mountain at 55 MPH and drawing 45 kW at that point. I've never seen it have this kind of behavior under normal circumstances, however.

 

[RegGuheert]

Will we ever know if a cell or pack has gone bad? I am not worried about degradation, but what if a cell needs replacing. Would we ever know by going to the dealership for our annual checkup?

I bet that information could be read from the car's computer if someone could decode the messages.

That's what the CELL VOLTAGE LOSS INSPECTION test on page EVB-65 of the LEAF service manual tests for. Unfortunately, most dealers seem to run the test at the wrong SOC since it takes time to lower the SOC to the appropriate level and then recharge afterwards. (BTW, this would be a good way to know it was done incorrectly: if they give you back your LEAF with a full charge within five hours of completing the test.)

 

[GeekEV]

I too have noticed this behavior, but not always. I believe it's because that's usually the point at which I'd be hopping on the freeway...

 

[TimLee]

I noticed something similar yesterday.
Started at 100%. Drove 16 miles very fast.
Stopped the car, and I think it was still showing 7/12 bars.
I came back out, started the car, and it was showing 5/12 bars.
The software can only accurately know the state of charge of the battery in a power off state.
So it is possible that the inaccuracies of knowing the state of charge only showed up for me after the car was shut down and restarted.

 

[occ]

...
I would really suggest a Gidometer. It's especially useful when you're down below that point where you're no longer seeing DTE in miles the Guessometer.

At 67 miles I would expect to have between 7 and 10 miles remaining. I would have around 13 miles remaining when I hit LBW, and would probably hit LBW at ~64 miles the way I'm driving now (with around 4.6-4.7 miles/kWh efficiency). Using CC instead of my delicate size 10s would sap about 3 miles from that, bringing me to LBW at around 61 miles.

Verified pack degradation in my car is 11%.

How do you verify this? With a GID meter? Is there an acceptable "methodology" or is this something the Nissan can do? (Never mind the latter, wishful thinking)

Will we ever know if a cell or pack has gone bad? I am not worried about degradation, but what if a cell needs replacing. Would we ever know by going to the dealership for our annual checkup?

I bet that information could be read from the car's computer if someone could decode the messages.

This is what I'm skeptical about. How is a normal owner to know about a bad cell so he/she could bring it in to check? And if he doesn't know, would driving around prolonged period with a bad cell be worst for the pack as a whole?

And then there is this degradation that Nissan would consider "normal". Do we know if some "normal" lost of range isn't caused by an abnormal cell that should be under warrantee and fixed as soon as possible?

I noticed something similar yesterday.
Started at 100%. Drove 16 miles very fast.
Stopped the car, and I think it was still showing 7/12 bars.
I came back out, started the car, and it was showing 5/12 bars.
The software can only accurately know the state of charge of the battery in a power off state.
So it is possible that the inaccuracies of knowing the state of charge only showed up for me after the car was shut down and restarted.

Yes, the turning the car off-on I generally see this adjustment often, pretty much anywhere along any part of the range. I learned to live with that as normal now. But it seems like when I notice this, the tenth bar (3rd from the top) is usually the one that went fastest (from 11th to 9th really quickly), and usually while I'm driving.

This is very annoying. First the GOM, now this? - the GOB (Guess'O Bars) ?!

 

[planet4ever]

Occasionally we hear hint of a notion, which seems very curious to me, that the battery is discharged cell by cell. That isn't the way it happens. All cells are working together end to end and side by side all the time to power the car. The only way I can imagine a bad cell causing a loss of mileage on a single bar would be if you subscribed to the cell-by-cell theory.

Ray

 

[mwalsh]

How do you verify this? With a GID meter? Is there an acceptable "methodology" or is this something the Nissan can do? (Never mind the latter, wishful thinking)

Consult III can tell a Nissan Tech what the Gradual Capacity Loss Coefficient is for any LEAF. And from that one can extrapolate capacity loss as a percentage. While I did agree to not reveal the actual numbers for my car, in telling you what the extrapolation is rather than the actual GCLC, I don't feel I'm breaking that agreement. Particularly since I've been saying to anyone within earshot for months now that I felt my degradation was in range of 8-10%.

 

[RegGuheert]

This is what I'm skeptical about. How is a normal owner to know about a bad cell so he/she could bring it in to check?

If you have a cell go bad in your LEAF, you should lose range at a rate comparable to the capacity loss of the cell pair which is experiencing the failure. This is because the electronics monitor BOTH the overall pack voltage AND the individual voltages of the cell pairs (two cells in parallel).

And if he doesn't know, would driving around prolonged period with a bad cell be worst for the pack as a whole?

No. In fact, I would guess that the rest of the pack would be treated more gently as a cell failed since it would be exercised over a smaller range of SOCs.

 

[occ]

Occasionally we hear hint of a notion, which seems very curious to me, that the battery is discharged cell by cell. That isn't the way it happens. All cells are working together end to end and side by side all the time to power the car. The only way I can imagine a bad cell causing a loss of mileage on a single bar would be if you subscribed to the cell-by-cell theory.

Ray

I hear you, but what about the monitoring algorithm that sets those bars? Evidently, they are not very linear, nor consistent. The program to determine those bars is probably pretty involved, perhaps to the level of requiring info from the cell (or at minimum the cells in series). Perhaps at certain SOC, a bad cell can cause the Bars algorithm to behave differently than expected. I'm just thinking out of no real knowledge on my part here....just, strange behavior should be called attention to, and let the brainiacs here explain or speculate.

 

[RegGuheert]

I hear you, but what about the monitoring algorithm that sets those bars? Evidently, they are not very linear, nor consistent. The program to determine those bars is probably pretty involved, perhaps to the level of requiring info from the cell (or at minimum the cells in series). Perhaps at certain SOC, a bad cell can cause the Bars algorithm to behave differently than expected. I'm just thinking out of no real knowledge on my part here....just, strange behavior should be called attention to, and let the brainiacs here explain or speculate.

I think you have the right idea. Phil (Ingineer) has done quite a bit of testing of the behavior of the battery controller and finds that it does jump around some as the battery charges and discharges. Assumedly this is due to calibrations/corrections that it applies as it goes.

 

[occ]

How do you verify this? With a GID meter? Is there an acceptable "methodology" or is this something the Nissan can do? (Never mind the latter, wishful thinking)

Consult III can tell a Nissan Tech what the Gradual Capacity Loss Coefficient is for any LEAF. And from that one can extrapolate capacity loss as a percentage. While I did agree to not reveal the actual numbers for my car, in telling you what the extrapolation is rather than the actual GCLC, I don't feel I'm breaking that agreement. Particularly since I've been saying to anyone within earshot for months now that I felt my degradation was in range of 8-10%.

Do you mean then that Consult III is not something for the normal consumer? Is it only for Nissan to determine warrantee issues? If the capacity warrantee is spelled out concisely, I would want to know that info, wouldn't you?

 

[mwalsh]

Do you mean then that Consult III is not something for the normal consumer? Is it only for Nissan to determine warrantee issues? If the capacity warrantee is spelled out concisely, I would want to know that info, wouldn't you?

Well...as I said in another thread somewhere, there are a whole bunch of the Consult III screens which feature a button labeled "Print for Customer". And how many of us have actually received something printed out from Consult III? <insert sound of chirping crickets>

 

[FairwoodRed]

I'm convinced that most dealers do the cell voltage testing at a much higher SOC than they should. Measuring the cell pair voltages at a high SOC is pretty worthless since this battery pack is top balanced. Unless they gave you the voltage of the cells along with the differences, there is no way to know that they did it correctly.

Both of our cell pair voltage tests were done at low SOC and mine was at low battery warning. The printout that TaylorSFguy got had the actual cell voltages on it. I have a print out of the report from a prior visit, so they can be had. This particular Leaf tech is very on the ball and I would be surprised if something slipped past him. He is very enthusiastic and likes to talk about all things leaf.

I think he said that when a cell gets 20mV off the pack average, that a code will be set and the amber warning light will be lit on the dash. So I would expect a failed cell to also turn on the warning light.

TaylorSFguy and I had a good chat waiting for the dealer to QC our cars so we could go home.

 

[RegGuheert]

Both of our cell pair voltage tests were done at low SOC and mine was at low battery warning. The printout that TaylorSFguy got had the actual cell voltages on it. I have a print out of the report from a prior visit, so they can be had. This particular Leaf tech is very on the ball and I would be surprised if something slipped past him. He is very enthusiastic and likes to talk about all things leaf.

That's good to hear! There have been a lot of stories here about this test being done at a high SOC.