Weak cells

feichin

I've been driving a 30kw leaf since early 2016, almost 220,000 km with no issues.
I lost the first bar a couple of months ago at 207,000
In the last month the range has dropped massively, a lot more than I think can be put down to colder weather, which I have experience of over the last few winters.
ie. in good weather, I'd get to work with 35%+ remaining, recently that had dropped to around 20% which I put down to weather, but the last couple of days it has dropped to 6>7%
I checked leaf spy last night and it's saying that there are 5 "weak cells"
What does this mean?
Is it repairable?
what's it gonna cost?

...Ghost...

Use a granny charger a couple of times and let it fully balance. See how that goes for you. Worked for me.

feichin

...Ghost... wrote: »

Use a granny charger a couple of times and let it fully balance. See how that goes for you. Worked for me.

Should letting it fully charge at home overnight to the point that the 3 lights have gone out in the morning not have the same effect??
Unfortunately I don't have a granny lead.

charlieIRL

...Ghost... wrote: »

Use a granny charger a couple of times and let it fully balance. See how that goes for you. Worked for me.

Does that work for any EV?

KCross

feichin wrote: »

I've been driving a 30kw leaf since early 2016, almost 220,000 km with no issues.
I lost the first bar a couple of months ago at 207,000
In the last month the range has dropped massively, a lot more than I think can be put down to colder weather, which I have experience of over the last few winters.
ie. in good weather, I'd get to work with 35%+ remaining, recently that had dropped to around 20% which I put down to weather, but the last couple of days it has dropped to 6>7%
I checked leaf spy last night and it's saying that there are 5 "weak cells"
What does this mean?
Is it repairable?
what's it gonna cost?

LeafSpy will show "weak cells" when the SoC charge is low. Basically those 5 cells are at a much lower voltage than the others and then show up as weak. The pack is only as good as the weakest cell so if one cell is weak that dictates the overall SoC as the BMS has to protect that cell from further damage.

You'll need to go to Nissan I'd say.

Technically its not a warranty issue as you've only lost one bar but I'd book it in for a service and get them to give you an assessment and see if they will give you some goodwill (unlikely but worth a try).

feichin wrote: »

Should letting it fully charge at home overnight to the point that the 3 lights have gone out in the morning not have the same effect??
Unfortunately I don't have a granny lead.

Yes, it should. Balancing happens at the end. So as long as the car stopped the charge session rather than a timer it will be fully balanced.

Do you charge to 100% every night and let the car stop the charge?

slave1

I feel the very recent drop in range is a lot quicker/deeper than previous years

ED E

How does the BMS in a leaf(or other) handle a cell going dead short? Can it isolate the module?

unkel

KCross wrote: »

The pack is only as good as the weakest cell so if one cell is weak that dictates the overall SoC

If you have a simple pack with just one string in series and no active balancing, then yes that's the case

For EV batteries which always have cells in parallel as well and active balancing, it is not quite as dramatic as "a pack is only as good as the weakest cell"

What do you think happened if 1 of the 8000 18650 cells in a Tesla Model S went kaput? Pretty much nothing

Calahonda52

KCross wrote: »

...

Technically its not a warranty issue as you've only lost one bar but I'd book it in for a service and get them to give you an assessment and see if they will give you some goodwill (unlikely but worth a try)...

With 220,000 kms on the clock, is warranty not gone at 100,000?

DM1983

Calahonda52 wrote: »

With 220,000 kms on the clock, is warranty not gone at 100,000?

30kwh leafs have 8 year warranty up to 160k km but yes, in your case, gone. Please comment back on costs quoted to repair those dodgy cells. Will be of interest to many here in the future.

KCross

unkel wrote: »

If you have a simple pack with just one string in series and no active balancing, then yes that's the case

For EV batteries which always have cells in parallel as well and active balancing, it is not quite as dramatic as "a pack is only as good as the weakest cell"

What do you think happened if 1 of the 8000 18650 cells in a Tesla Model S went kaput? Pretty much nothing

I could be wrong but I think Tesla can isolate bad cells?

I dont believe Nissan are as sophisticated on the L24. From my understanding when a cell goes "bad" you get a large drop in usable range as the BMS has to protect that cell going any lower, voltage wise, and so you see low battery and turtle mode much earlier.

Replace the bad cell and its back to normal again so that weak cell has a disproportionate affect on the pack.

KCross

Calahonda52 wrote: »

With 220,000 kms on the clock, is warranty not gone at 100,000?

For the L30 I think its 8yrs or 160,000km's so, yes, warranty has passed but I'd be looking for goodwill from them.

A few appropriately worded tweets on their feed showing how a 3yr old battery is acting up will get a response, imo!

Paying to replace a module is about £1500 in the UK from 3rd party company (Indra). Not sure if anyone is setup to do it here other than Nissan.

...Ghost...

charlieIRL wrote: »

Does that work for any EV?

I can only speak for it working for the Leaf

feichin

Thanks for all the replies.
I knew from day 1 that I was going to kill the warranty in 3>4 years so that is not an issue
(but I wouldn't refuse some "goodwill" if there was any going!!!)
Just curious to know if anyone else has had similar issues??? or what it might cost to repair (if that's possible)

"Do you charge to 100% every night and let the car stop the charge?"
***The short answer is yes, occasionally if I had driven right down to limit (rarely) it might not be fully charged by the morning, but that would be the exception rather than the rule

"Paying to replace a module is about £1500 in the UK from 3rd party company (Indra). Not sure if anyone is setup to do it here other than Nissan."
***Is a module a cell? a group of cells? or the entire battery?

"Please comment back on costs quoted to repair those dodgy cells. Will be of interest to many here in the future."
*** I'll get Nissan dealer to take a look next week and report back how that goes.

LeBash

A bit off topic but what is the best way to keep the cells in good shape? Manual in a kona says fully discharge the battery once per month and give it a full charge.

I was on a fast charger for about 4 month (not alot, only 7000km on it in 10 months).

Just used fast charger once since, when I got stuck but other wise I drop it into the last 10% every month and put a full charge on while in work. From time to time when I'm going somewhere and the range will be tight I'll throw it on the AC for a couple of hours.

Noticed at 100% it's not showing 447km but only 402km in the last couple of weeks. Thought I read the cold will effect the batteries and maybe that was it.

JPA

I think it was Unkel that mentioned a place in Dublin that will swap out bad cells. Might need to him to contribute here!

unkel

JPA wrote: »

I think it was Unkel that mentioned a place in Dublin that will swap out bad cells. Might need to him to contribute here!

I know of a garage that is a Bosch accredited training centre (with an excellent reputation for diagnostics) and they have been moving into hybrid / PHEV / BEV in recent years. Give them a call, MKW motors, just of the M7 at Kingswood Business Park (01) 459 5266

KCross wrote: »

I could be wrong but I think Tesla can isolate bad cells?

You're half right. Tesla can't isolate bad cells, but the cells are connected onto the bus bars with just fuse wire. So if a cell shorts, overcharges or any other way gets hot, the fuse wire just melts and the rest of the pack goes ahead without the help of their comrade in full safety

See this linky watch for just one minute and you get the idea

Jonnykitedude

feichin wrote: »

Thanks for all the replies.
I knew from day 1 that I was going to kill the warranty in 3>4 years so that is not an issue
(but I wouldn't refuse some "goodwill" if there was any going!!!)
Just curious to know if anyone else has had similar issues??? or what it might cost to repair (if that's possible)

"Do you charge to 100% every night and let the car stop the charge?"
***The short answer is yes, occasionally if I had driven right down to limit (rarely) it might not be fully charged by the morning, but that would be the exception rather than the rule

"Paying to replace a module is about £1500 in the UK from 3rd party company (Indra). Not sure if anyone is setup to do it here other than Nissan."
***Is a module a cell? a group of cells? or the entire battery?

"Please comment back on costs quoted to repair those dodgy cells. Will be of interest to many here in the future."
*** I'll get Nissan dealer to take a look next week and report back how that goes.

If you can get your hands on a used pack from a breaker leaf you can easily swap out each individual cell yourself. Its really straight forward once you have access to a lift and something to drop the pack out from under the car with. Wont be "new" but you'll see a dramatic increase, once the breaker pack has less KM on it than your existing one.

Old diesel

One potential issue is that IF it's the same as Leaf 40 then the new cells need balancing to the ones in the car.

Chap I know of on twitter had cell issues with his 40 and Nissan messed up the first attempt.

Because the new ones were showing higher volts then what was there and basically when they are full - that's the rest of them full even they arent really full.

So my guy was still getting similar symptoms with the new cells but for the opposite reason.

If it's a complete pack from the breakers then I'd just swop up the whole pack tbh.

You just can't swap out Li cells from one used pack to another.

First you got to check the cell resistance and how they actually perform under charge and discharge loads, a battery will always be limited by the weaker cells.

You also got to be sure you know that your funeral will take place shortly after a mistake with 380-400 volts DC, there is no 2nd chance. So you need to know what you're doing and have the proper PPE and insulated tools, gloves that are in date etc.

As Old Diesel said above, best would be swap the entire battery and a lot safer.

Old diesel

Deleted User wrote: »

You just can't swap out Li cells from one used pack to another.

First you got to check the cell resistance and how they actually perform under charge and discharge loads, a battery will always be limited by the weaker cells.

You also got to be sure you know that your funeral will take place shortly after a mistake with 380-400 volts DC, there is no 2nd chance. So you need to know what you're doing and have the proper PPE and insulated tools, gloves that are in date etc.

As Old Diesel said above, best would be swap the entire battery and a lot safer.

Should be okay to put brand new cells in IF the person doing the work knows what they are doing.

That's a big IF though.

The chap on twitter ran into issues because whoever at Nissan did the job didn't do it perfectly.

So it wasn't changing cells per se that was at fault.

Old diesel

Old diesel wrote: »

Should be okay to put brand new cells in IF the person doing the work knows what they are doing.

That's a big IF though.

The chap on twitter ran into issues because whoever at Nissan did the job didn't do it perfectly.

So it wasn't changing cells per se that was at fault.

I’ve never heard anyone mixing old cells with new ones it just shouldn’t happen, there no point And it would be a waste of new cells and it’s probably the reason there is issues with the mentioned pack.

Jonnykitedude

Old diesel wrote: »

If it's a complete pack from the breakers then I'd just swop up the whole pack tbh.

Sorry that's what I was referring to.

You can take each individual cell out from any mk1 or mk 1.5 and replace with any car from same period given you use the same wiring loom, buzz bars and BMS from your car. Its a simple enough procedure. The BMS from your car will have to "learn" the new cells so readings will be off for a bit but if you teach it the lower limit of the cells it'll pick its parameters up pretty quickly.

Jonnykitedude

Also, the make up of battery casing from mk1 and mk1.5 is ever so different. So a straight swap cant be achieved.

Just to note.....Mk1 models of leaf (built in japan) are put together much better than the later models which came from UK, battery build is far better in japan versions.......like Japan uses nuts and bolts......UK uses version of tech 7.....I kid you not!

Old diesel

Deleted User wrote: »

I’ve never heard anyone mixing old cells with new ones it just shouldn’t happen, there no point And it would be a waste of new cells and it’s probably the reason there is issues with the mentioned pack.

Apologies........

I made a mistake - it was new modules the guy got fitted to his car and it was the pack that wasn't balanced correctly during that process.

I found his blog post about it.

Old diesel

Old diesel wrote: »

Apologies........

I made a mistake - it was new modules the guy got fitted to his car and it was the pack that wasn't balanced correctly during that process.

I found his blog post about it.

It would still be rather odd to mix old Lithium with new, older batteries will go out of balance faster dip in voltage faster when under load and heat up faster when charging on DC and under load.

It doesn't make sense because Nissan have stated they only guarantee around 75% - 80% capacity so unless they're having trouble finding older cells they could be chancing their arm , hoping for the best by installing new modules.

Deleted User

Deleted User wrote: »

It would still be rather odd to mix old Lithium with new, older batteries will go out of balance faster dip in voltage faster when under load and heat up faster when charging on DC and under load.

It doesn't make sense because Nissan have stated they only guarantee around 75% - 80% capacity so unless they're having trouble finding older cells they could be chancing their arm , hoping for the best by installing new modules.

If one or two modules fail that's exactly what Nissan are doing, i.e. they slap in minimum number of brand new modules there. Who knows, they might even have slightly different chemistry in them for a bit more capacity compared to the originals. Those new modules will of course end up having a different discharge behaviour from the the rest but the important thing is that their voltage stays at least above the other modules. That way the repaired pack will be limited by the next weakest of the original modules.

samih

samih wrote: »

If one or two modules fail that's exactly what Nissan are doing, i.e. they slap in minimum number of brand new modules there. Who knows, they might even have slightly different chemistry in them for a bit more capacity compared to the originals. Those new modules will of course end up having a different discharge behaviour from the the rest but the important thing is that their voltage stays at least above the other modules. That way the repaired pack will be limited by the next weakest of the original modules.

I suppose it saves messing around trying to match so many different cells, it's very odd behaviour though.