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Discussion Starter #1
I was getting a free charge and coffee at my local Nissan dealer (wow; these peeps are friendly and helpful !), and asked whether they'd heard about the Nissan Japan battery replacement option and if it was coming to the UK. They hadn't. But, they did tell me that they could improve SoH and range by replacing 2-3 cells at a cost of £6-700. I'll check this with the service manager during the week (wasn't there on a Saturday); apparently they've done this before (and recently).

Has anyone come across this before ? I'm rather doubtful that replacing 2 or 3 cells will return a battery to better health - there are lots of cells, so surely it would be a very limited effect ? (or, is the whole battery performance limited by the weakest cells... if so, then losing the weakest might make a difference assuming that the others are a lot stronger). No, i'm not an electrical engineer :)

This is for a 2012 Leaf, 16k miles, 80% SoH (Leafspy), one bar lost off display, working range about 60 miles. It's in great condition and a better range/battery would be super.

Opinions ?
 

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I was getting a free charge and coffee at my local Nissan dealer (wow; these peeps are friendly and helpful !), and asked whether they'd heard about the Nissan Japan battery replacement option and if it was coming to the UK. They hadn't. But, they did tell me that they could improve SoH and range by replacing 2-3 cells at a cost of £6-700. I'll check this with the service manager during the week (wasn't there on a Saturday); apparently they've done this before (and recently).

Has anyone come across this before ? I'm rather doubtful that replacing 2 or 3 cells will return a battery to better health - there are lots of cells, so surely it would be a very limited effect ? (or, is the whole battery performance limited by the weakest cells... if so, then losing the weakest might make a difference assuming that the others are a lot stronger). No, i'm not an electrical engineer :)

This is for a 2012 Leaf, 16k miles, 80% SoH (Leafspy), one bar lost off display, working range about 60 miles. It's in great condition and a better range/battery would be super.

Opinions ?
Leafspy should tell you if any cells are significantly lower than the others.
If there are a few low then replacing some will help (I guess).
If they're all equally degraded, then it won't help.
 

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As above, generally if one or more cells have deteriorated significantly it dramatically reduces the range to less than 30 miles. Replacing the cell(s) in that case is worthwhile, but your figures sound more likely to be down to age related deterioration of the whole pack.
The price quoted is incredibly good value if it is parts and labour - I suspect it may just be the parts. To drop the battery pack, split the cases, switch the cell(s) which inevitably be the ones in the least accessible places, reseal the case, refit and test is quite a few hours work (say 10) which at stealer rates is a lot more than that.
 

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Maybe Nissan have realised that quoting a sensible amount for cell replacement creates less of a PR problem than old leafs being scrapped because they've lost enough range to make them useless before they're anywhere near the age you'd expect a car to be scrapped at?
 

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I think that you are crediting them with a great amount of conscience. Given the changes in control we are all on our own after 5 years at best.
The real issue is that too many of the early adopters had them as third cars and often mistreated them by leaving them at 100% charge for long periods.
An equivalent car such as a Pulsar is long gone from the manufacturer's memory by this age. They may have done greater mileages but it is only the age that matters to the manufacturer. Otherwise why don't they do PCP over more than 4 years?
 

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Maybe ask then to do tests mentioned here if you are within warranty period and having cell issues


- Leaf 30 kWh
Sent from mobile phone so please mind the typos
 

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Discussion Starter #8
Thanks for the advice.
I'm thinking that the cells usually look fairly equal, and i've never seen one consistently down relative to the others. A screenshot of Leafspy is below - seems to look OK ?

124563
 

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Discussion Starter #9
Since it's a 2012, i'm pretty sure that there's no warranty on the battery (?).

Also - i sometime see that some cells/bars are red in Leafspy - what does that indicate ? The red ones are in different places, and not consistent either...

A relate Leafspy question - i want to turn off the reverse beep - i can see it in the 'service menu' VSP settings, but it says 'not supported' when i try, the 'buttons' won't become active. Any suggestions ?
 

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Discussion Starter #10
I had a cell (or several ?) replaced earlier this year
see : https://www.speakev.com/threads/service-ev-system-help.132204 for details
I didn't notice any difference in range (either from GOM or experience) after that.
Thanks - and sorry to hear that your experience was 'less than optimal'.

I think your situation shows that a completely dud cell(s) will compromise the battery function totally. This would suggest that overall performance is limited by 'the weakest cell'. Then one might extrapolate that if there is one or more really weak cells among a majority of good ones; then replacing those would have a big effect. But, i'm no electrical engineer... and this is conjecture :)

I've sent the Service manager of my local dealer an email - will see what he says.
 

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You are correct, a bad cell reduces the performance of the overall pack hence why replacement can make a significant difference in some cases. Here is an example of a pack with two bad cells:

124567


There is a lot in this screenshot from LEAFSpy
  • two cells (the pair 57 & 58) are 153mV down from the highest
  • the red bars show cells that the LEAF BMS has tried to shunt the good cells charging down to match the voltage of the bad cells by including extra resistance, but the difference is too high for it to manage
  • Note the high SOH and SOC figures which might imply that all is well - clearly it is not!
  • At this point the car had a range of less than 20 miles
The full story of the owners impressive work to fix this is here. Note that he clearly is both good with spanners and confident with electrics and IT. Whether many others should be DIY'ing this sort of work is open to question, although I note that both this gent and @MikeSchooling started like this before building their businesses.

Looking at your screengrab shows less of a difference but again isn't all of the picture. You need to look at both high and low charge states to see where the total out of balance is worst. What does yours look like when fully charged? How close to 100% SOC can you get?

Duncan
 

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Thanks - and sorry to hear that your experience was 'less than optimal'.
It wasn't that bad. I was actually using my 'spare' car and being paid by Nissan for all the fuel added to it so wasn't really out of pocket - indeed slightly better off in that I wasn't paying for electricity either. Still very annoying that my supplying dealer had no EV technician at that time and the next nearest dealer that had one weren't treating it as urgent.
 

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A Czech Leaf owner had a few bad cells and that resulted in very low actual usage before turtle mode (50 miles) though SoH was high.

The replacement while didn't improve SoH resulted in being able to use 80 miles without turtle the day after replacement. He though forked out as Nissan didn't find any issues and turned him away

- Leaf 30 kWh
Sent from mobile phone so please mind the typos
 

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Discussion Starter #15
You are correct, a bad cell reduces the performance of the overall pack hence why replacement can make a significant difference in some cases. Here is an example of a pack with two bad cells:

View attachment 124567

There is a lot in this screenshot from LEAFSpy
  • two cells (the pair 57 & 58) are 153mV down from the highest
  • the red bars show cells that the LEAF BMS has tried to shunt the good cells charging down to match the voltage of the bad cells by including extra resistance, but the difference is too high for it to manage
  • Note the high SOH and SOC figures which might imply that all is well - clearly it is not!
  • At this point the car had a range of less than 20 miles
The full story of the owners impressive work to fix this is here. Note that he clearly is both good with spanners and confident with electrics and IT. Whether many others should be DIY'ing this sort of work is open to question, although I note that both this gent and @MikeSchooling started like this before building their businesses.

Looking at your screengrab shows less of a difference but again isn't all of the picture. You need to look at both high and low charge states to see where the total out of balance is worst. What does yours look like when fully charged? How close to 100% SOC can you get?

Duncan
Thanks; that's quite a story and an impressive skill level. While i'm OK to take cars apart, i've little or no electrical expertise. Thus, i'm thinking that it won't be me doing any repairs/upgrades.

I charged last night, and this is the reading after a very short drive - i'm able to charge to about 85%.

I've not the technical wits to work out what the various numbers in Leafspy mean - a translation would be gratefully received !
124570

124571
 

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Ok, here goes - some obvious, some less so:
  • AHr (Amp Hours) - for the total pack
  • SOH State of Health - a combination figure based on the pack as a whole and the type of charges. The figure can be misleading - see later
  • 389.17 - total voltage over all cells - ideal would be 4.10 x 48 x 2 = 393.6 so good
  • Hx - not a clue - it is a strange measurement!
  • 26mV - the imbalence between the cells when fully charged - it was 19mV when 42% charged in the early screengrab. These are normal figures and show a relatively normal degree of imbalence which you can improve with an occassional rapid charge.
  • min/avg/max - the various cell voltages
  • SOC - not too bad - this only starts at 95% as the full capacity isn't used to improve life. Was that really fully charged or was there a bit more to go as this is normally at a peak when the max cell voltage figure above is 4.1 and yours only showed 4.066? Presumably not given the "short drive" mentioned.
  • 15.7kWh - this is the killer - you might have had 21kWh originally assuming all cells at 4.1v and all with full capacity
  • 72.2% GID - the 203 - is the best measure out of 292 - named after Gary Giddings who found this measurement.
Bluntly your battery has aged (haven't we all since 2011 ;)) but as it hasn't been exercised particularly well it has degraded somewhat to between 2/3rds and 3/4 of its original capacity. I note that the range is calculated at 4.0 miles/kWh which is low but depends on your driving type and only influences the GOM. There is no obviously bad cell/cells that could be changed to make a significant difference (unlike the case I quoted above), and the only simple improvements are to rebalance all of the cells by a rapid charge or a larger capacity battery. If considering the latter, don't think that you are going from 15.7kWh to (say) 30kWh - all batteries are limited to 95% of theoretical capacity and any secondhand battery will have lost significant capacity - the first "bar" is only lost at 85%.

Hope that helps

Duncan

Edited to add - what is your normal maximum daily mileage? Mine is about 60 so going to a bigger battery (say a 40 kWh) is a waste as I'll only rarely use the greater capacity. Currently I resort to using an ICE - roughly once every 4 months - which is much cheaper than a battery swap. If my range falls below 60 (plus a sefety margin) it'll be time to act.
 

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Discussion Starter #17
Ok, here goes - some obvious, some less so:
  • AHr (Amp Hours) - for the total pack
  • SOH State of Health - a combination figure based on the pack as a whole and the type of charges. The figure can be misleading - see later
  • 389.17 - total voltage over all cells - ideal would be 4.10 x 48 x 2 = 393.6 so good
  • Hx - not a clue - it is a strange measurement!
  • 26mV - the imbalence between the cells when fully charged - it was 19mV when 42% charged in the early screengrab. These are normal figures and show a relatively normal degree of imbalence which you can improve with an occassional rapid charge.
  • min/avg/max - the various cell voltages
  • SOC - not too bad - this only starts at 95% as the full capacity isn't used to improve life. Was that really fully charged or was there a bit more to go as this is normally at a peak when the max cell voltage figure above is 4.1 and yours only showed 4.066? Presumably not given the "short drive" mentioned.
  • 15.7kWh - this is the killer - you might have had 21kWh originally assuming all cells at 4.1v and all with full capacity
  • 72.2% GID - the 203 - is the best measure out of 292 - named after Gary Giddings who found this measurement.
Bluntly your battery has aged (haven't we all since 2011 ;)) but as it hasn't been exercised particularly well it has degraded somewhat to between 2/3rds and 3/4 of its original capacity. I note that the range is calculated at 4.0 miles/kWh which is low but depends on your driving type and only influences the GOM. There is no obviously bad cell/cells that could be changed to make a significant difference (unlike the case I quoted above), and the only simple improvements are to rebalance all of the cells by a rapid charge or a larger capacity battery. If considering the latter, don't think that you are going from 15.7kWh to (say) 30kWh - all batteries are limited to 95% of theoretical capacity and any secondhand battery will have lost significant capacity - the first "bar" is only lost at 85%.

Hope that helps

Duncan

Edited to add - what is your normal maximum daily mileage? Mine is about 60 so going to a bigger battery (say a 40 kWh) is a waste as I'll only rarely use the greater capacity. Currently I resort to using an ICE - roughly once every 4 months - which is much cheaper than a battery swap. If my range falls below 60 (plus a sefety margin) it'll be time to act.
Hi Duncan,

Thanks for the detailed diagnosis and information - very much appreciated.

Good to know that it's working as well as can be expected for its age, and that a cell replacement isn't likely to make a difference. It was previously owned by Perth council, and i'd think it possible that it might have been left fully charged most/much of the time. A guess.

Yes, the short drive took one bar off; i think that my range is about 60miles - based upon a single drive that i did in the summer (at a steady 50-60 mph, along a quite stretch of the A1, in Scotland).

Currently, the car is used by my wife for a short commute about 14 miles roundtrip (?). She has a charger at her workplace (and home). So, the capacity is easily enough for this. Plus, we use it for driving around town and local trips. Many/most destinations up here (Scotland) have a charger, so we can visit most places on short-ish trips.

The reason why i'd like a bigger battery, is the prospect of doing a 115mile trip to see the in-laws. Currently, i should be able to do it with one charge half way, but have generally done 2 charges as i hate 'playing chicken with the gas gague'. We don't do this trip that often, so it's not really justifiable.

Finally - rapid charging; how frequently would help ? Currently my wife charges it to 80% on the timer before driving, and we rarely rapid charge. However, we've a rapid within walking distance (and free, for now), so could do this regularly if it might help.

Thanks again :)
 

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Discussion Starter #18
Wasn't the battery warranty for 8 years back then ? If it was there will be at least a month and maybe up to 13months left of the warranty period.
FYI, i've found the original documentation, and it was a 5 year warranty from Nissan on the battery - starting from March 2012. Thus, expired.
 

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Finally - rapid charging; how frequently would help ? Currently my wife charges it to 80% on the timer before driving, and we rarely rapid charge.
I would set the timer to charge to 100% at least once or twice a week as this appears to help with cell balancing (but make sure your wife is aware that on the first corner after leaving home with 100% charge, the brakes will feel a bit less effective as there is little or no regen braking when the battery charge % is in the high 90's)
 

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Good advice re-the regenerative braking being reduced dramatically above 80% charge.

My understanding is that rapid charging is more effective at cell balancing than 100% charging, but I stand to be corrected.

In terms of your occasional long journeys, speed is a major factor in electricity consumption so just knocking off 5 MPH makes a major difference and may be enough in the marginal need for a second charge. You could also look at increasing tyre pressures and blanking the front grille which make a different if you haven't already done so.
 
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