Timecapsule 2015, dodgy battery troubleshooting

Impressive work Dala. Hope this fixes those cells and that they stay healthy for a long time.

After charging the cell up and letting it sit for 16h, it unfortunately drooped back a few mV, indicating high internal resistance. It will have to be replaced in the future, but the car should be usable now, so I spritzed some bathroom silicone around the battery, and popped it back in to the car.

I then plugged the charger back in, and tadaa, the blue dash charge leds lit up!


The leafspy now reports a 46mV diff, heck of a lot less than 150-225 range before!


The GOM happily reports a total 177km range now, but I need to just drive it and see what the actual range is.


I took it for a test drive, and got 35km with loosing only two bars. That trip would have been impossible pre-surgery!

Now I will start the process to try and get my hands on a good low-mileage Gen2 cell from another 24kWh leaf...

Great work! You turned a write-off of a Leaf into an average driver. I hope the cells have found their 'natural balance' for their condition, and stay there.

Amazing work... Nice to see a forum member that can really attack this car...

COULD I ASK YOU FOR AN AMAZING FAVOR THAT CAN BENEFIT ALL OF US MECHANICAL TYPES?

PLEASE WRITE A LIST OF THE PROCEDURE OF HOW YOU TOOK OUT THE BATTERY....

I would love, down the road to try replacing a battery on my own....

Since you know they're bad, you may wish to replace the two cells as soon as possible. If you wait too long, the BMS may remove a health bar, making yours an 11 bar car. Unless you know how to do a BMS reset, you'll be stuck with an <12 bar car with a good battery.

Dala said:

After charging the cell up and letting it sit for 16h, it unfortunately drooped back a few mV, indicating high internal resistance.

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Could you explain why the voltage droop indicates high internal resistance? Is this due to the re-balancing going on or is this just how Li cells degrade or am I just missing it?

And once again, very nice work and thanks for sharing!

Great way to stave off reality for what I think will be a few weeks at the most. Balancing happens all the time and every second, those two cells will fall farther and farther behind. I would replace them ASAP if not sooner.

I worry that the real problem is a bad BMS. For some reason, perhaps the BMS is always discharging these cells.

WetEV said:

I worry that the real problem is a bad BMS. For some reason, perhaps the BMS is always discharging these cells.

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Should be able to swap leads with other cells (obviously tag them first) to verify.

powersurge said:

Amazing work... Nice to see a forum member that can really attack this car...

COULD I ASK YOU FOR AN AMAZING FAVOR THAT CAN BENEFIT ALL OF US MECHANICAL TYPES?

PLEASE WRITE A LIST OF THE PROCEDURE OF HOW YOU TOOK OUT THE BATTERY....

I would love, down the road to try replacing a battery on my own....

Click to expand...

I watched two youtube videos before attempting this, they showed this much more in detail. Just google Nissan Leaf Battery Removal, they are gold!

Lothsahn said:

Since you know they're bad, you may wish to replace the two cells as soon as possible. If you wait too long, the BMS may remove a health bar, making yours an 11 bar car. Unless you know how to do a BMS reset, you'll be stuck with an <12 bar car with a good battery.

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Noted, It is strange how this hasn't already happened, the previous owner seems to have put 700km on it in this shitty state somehow! Replacing is still top prio!

goldbrick said:

Could you explain why the voltage droop indicates high internal resistance? Is this due to the re-balancing going on or is this just how Li cells degrade or am I just missing it?

And once again, very nice work and thanks for sharing!

Click to expand...

Ofcourse! I've done tons of Lithium 18650 battery salvaging in the past, and that involves running them thru a capacity check. When dealing with lithium of unknown quality, the first step is to charge it up and let it sit at maximum voltage for a day or two. If any significant vdroop occurs, internal resistance due to microscopic cracks inside is usually the reason, and the cell needs to be recycled.

DaveinOlyWA said:

Great way to stave off reality for what I think will be a few weeks at the most. Balancing happens all the time and every second, those two cells will fall farther and farther behind. I would replace them ASAP if not sooner.

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Yeah I know, I just need this for a daily driver while I wait for a cell

WetEV said:

I worry that the real problem is a bad BMS. For some reason, perhaps the BMS is always discharging these cells.

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Yeah as ElectricEddy also said, when I do the actual replacement, After replacing the cell, I intend to also swap the 57&58 with say 59&60 to get a baseline of the BSM state.

Thanks to all involved, this forum is great!

I don't suppose it ever threw any DTC codes, what we might look for if running into a similar situation. Check with Leaf spy in the service menu-enable service screen/ Read DTCs.
Possible cell over discharge P3375-P338C or ASIC open P33E6 for example.
Please report back if any found.

ElectricEddy said:

I don't suppose it ever threw any DTC codes, what we might look for if running into a similar situation. Check with Leaf spy in the service menu-enable service screen/ Read DTCs.
Possible cell over discharge P3375-P338C or ASIC open P33E6 for example.
Please report back if any found.

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Yeah I'm kicking myself for not checking the actual codes it threw while in limp mode. But if they get the chance to come back before I get the new cell, I'll def post here.

Now done 50km since last charge, car still says it can do 120km (I know it wont) but let's see Feels good to be able to use it

Dala said:

ElectricEddy said:

I don't suppose it ever threw any DTC codes, what we might look for if running into a similar situation. Check with Leaf spy in the service menu-enable service screen/ Read DTCs.
Possible cell over discharge P3375-P338C or ASIC open P33E6 for example.
Please report back if any found.

Click to expand...

Yeah I'm kicking myself for not checking the actual codes it threw while in limp mode. But if they get the chance to come back before I get the new cell, I'll def post here.

Now done 50km since last charge, car still says it can do 120km (I know it wont) but let's see Feels good to be able to use it

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They should still be there unless you cleared them with Leafspy.
My question is if Nissan is hesitant on performing battery pack warranty work ( under "normal circumstances") unless it throws a DTC code, than there could be a lot of Leafs out there with weak cells causing ltd range or sudden turtle.

@Dala did you change the cell yet?

kahi said:

@Dala did you change the cell yet?

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I did not yet, I have ordered two, but in the meantime I am testing out bottom balancing it properly, this will also aid in the future when I swap the cell.

So I got in contact with EVs Enhaced, and they gave me some pointers in how to better balance manually. Here are the steps I'm gonna do

1) Discharge the pack to a lowish point - the two cells will limit how far you can discharge of course
2) Remove the pack again and re-open it
3) Charge the two cells to significantly higher voltage than the rest of the cells in the pack
4) Temporarily, reinstall the pack into the car and continue to discharge (lights/heater/etc on) until all the cells in the pack (except the two higher ones) are in the 3.0-3.3V range. This time the two cells wont be limiting your ability to discharge the pack
5) Remove the pack and this time discharge the two cells to match the voltage of the rest of the cells - so they are all bottom-end balanced. Leave the cells to settle for a day after discharging to re-check the voltage and discharge further if required.
6) Reinstall the back and fully charge it - if the two cells hit 4.12V while charging before the rest of the other cells then they are certainly lower capacity so replacing them would increase range to some extent. If other cells in the pack hit 4.12V before the two cells, then this replacement module has equal or better capacity compared to the rest in the pack - replacing it would give you no benefit.

Here is a screenshot from point 3


Here is a screenshot from completed point 4


Still waiting a day for it to settle, then I'm gonna rebalance at close to 0 SOC and seal it back up. Watch this space.

the amount of work you did for this is crazy! how could nissan sell a car with a battery this dodgy?

The reality is all manufactured goods have defects and stuff happens. These failures are quite rare and covered by warranty, except in rare circumstances like Dala's.

I understand you're frustrated about your car, but stuff happens. We're here to help you if we can, if you provide the info requested in your thread.

Some additional information
- The cell was replaced by the previous owner. He did not have any concept of balancing. Nissan is not at blame with this vehicle
- Never balance at middle SOC. Always do it at extremes, like fully charged or fully discharged. There is too much variance in the middle. Bottom balancing is best for EVs, to get maximum range.
- After my initial shitty middle balancing, the car made 85km possible. Let's see how much a proper balancing helps!

So I finished the bottom balancing. Here are the results

I was hoping to get a peek of the model number for the shitty replaced cell, but unfortunately it is below the visible sheet metal.


Here is the car, fully charged. Note that it only goes to 83% SOC, limited by the shitty degraded cell that hits 4.1V before the rest.


After driving it for 15km.


After driving it for 30km


Noticed that the fully charged GOM now says 140km instead of 180km. The bars are also lost quicker up top now (expected!) but should now be a bit more stable at lower SOC.

This concludes manual balancing. Now the next step is to actually replace the module. The bottom balancing will probably squeeze out a few more km's, might even be able to hit >100km now, but cell replacement is inevitable.

This thread has taught me a lot. Thanks for sharing and good luck with the new module.