Dala's Leaf buildthread (2015 Nissan Leaf)

Dala

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Feb 16, 2018
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So I thought I might start a project thread on this car, that wasnt supposed to be a project.
I recently picked up a commuter, 2015 ZE0 24kWh Nissan Leaf, with 5k km on it. It has extremely low range, the guess-o-meter(GOM) on the dash says 160km, but as soon as you start driving it you are lucky if you manage 20km. Pretty shite for 15000 :D (Yes these cars are extremely expensive in Finland!)

Due to this being an USA model imported to Europe, so I apparently dont have any battery warranties in place. I also wasnt fully aware that the battery was this bad, so if I could go back in time I would have never bought this car.
But nevertheless, lets stay positive and start fixing this car up.
Heres a picture of the bog standard car. Not much to say really. Was a wet day.

image_pskqne.jpg

The car seems to deplete about 3-4kWh of battery, and then promptly report it as empty. This is strange, since its supposed to be a 24kWh battery! Charging it back up also goes suspiciously fast, so something is indicating that one or more cells are dragging the whole pack down.

It also goes into turtle mode from time to time, and with a handful of dash warnings and load reductions.

image_jyhtqn.jpg

So next order of business is to start diagnosing the battery. The CAN communication needs to be forwarded to a phone running the LeasSpy Pro app. This is achieved with a bog standard v1.5 ELM327 Bluetooth OBD2 dongle. Note that it has to be v1.5, the cut down v2.1 wont work.

So here are some screenshots from a fully charged battery. Notice anything suspicious? :D

image_jdpjmw.jpg

So as you can see, the cellpair 57&58 are down 150mV from the rest of the cells. The Nissan battery management system utilizes passive balancing of the lithium cells using shunt resistors. Unfortunately, these are not very beefy, and can only bypass a few mA when charging. So if any cells have drifted far enough, and ESPECIALLY when replacing cells, you need to pre-balance them before you insert them into the pack.

So a manual rebalance of 57&58 seems like the best way forward. Later down the line I can always replace them, but lets start with a rebalance.

First thing to do is disconnect the 12V battery in the front, or else the control system will freak out when I start disconnecting HV stuff

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Next thing to disconnect is the fuse from the HVDC pack. The fuse is located under the floor, and can be accessed via a panel in the backseat floor.

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After pulling the fuse, it is now safer to work under the car, and next step is to disconnect the high voltage cabling from the pack. Notice that Im wearing Class 0 high voltage gloves each time Im near anything labelled orange.

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Started propping up the car high with multiple failsafes.

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Removed splash plates. There are three of them.

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Here are the battery high voltage connections and CAN cabling, disconnected them. They were quite hard to figure out how to open.

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I then put pressure on battery with some wood and four jacks, started loosening bolts. There were 18mm, 8 in total.

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Built a dolly to be able to slide the pack around. The battery weighs circa 280kg!

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Lowered battery onto dolly

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Then it was very easy to slide the battery out

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For some reason they dont want you to be able to open it easily. It was glued shut, but with the help of some prying and cutting tools, it eventually came apart

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Here is the battery exposed. Several stacks of modules, totalling at about 400V DC. Safety first, so gloves on at all times now!

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I then started to charging. Decided to take it slow due to not knowing much about the Li-MnO2 cells (I'm more of an 18650 guy :D) Since the cellpair 57&58 was at the absolute bottom of the stack, they will be extremely hard to get to. I don't want to disassemble the pack, so I improvised some sticky leads with hard drive magnets inside alligator clips. That way I can just lower them down into the pack, and they will stick to the terminals.

image_vycztu.jpg


I then hooked up a bench supply, set it to 8.4V and connected it to the outer terminals of the 2S cell. I am lucky that the rest of the pack is at 4.00V cell average, so I wont have to worry about CC/CV switchover, just CC charging up to 4V (8V effective due to 2S). As charge current limiter, I set it to 0.3Amps, to keep temps and everything nice and smooth.

image_qpvcjl.jpg


I also disconnected some of the BMS leads, don't know if this was necessary, and hope I don't break the BMS by piggyback charging this way.

After 18h of charging, the cells are up from 3.80V -> 3.95V, so just a few more mV to go to 4.00V
 
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Sean

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Oct 8, 2016
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Where is the leafspy screenshot showing per cell voltages when it's in limited power mode ?

Nissan would have resolved this issue for you, given it's age, despite you being slightly remote and despite wthe vehicles history- but you've obviouslyvoided that warrenty now.

I've donethe same as you a number of time, if you need a source of gen 2 cells let me know.

I'm assuming you've left it plugged in on the home charger for at least 48 hours ?, when there is such an imbalance the process does take a while - but, seeing as you have allready done most of the work required to get access to what is potentially a very weak cell, why not just replace it now ?
 

Dala

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Messages
205
Sean said:
Where is the leafspy screenshot showing per cell voltages when it's in limited power mode ?

Nissan would have resolved this issue for you, given it's age, despite you being slightly remote and despite wthe vehicles history- but you've obviouslyvoided that warrenty now.

I've donethe same as you a number of time, if you need a source of gen 2 cells let me know.

I'm assuming you've left it plugged in on the home charger for at least 48 hours ?, when there is such an imbalance the process does take a while - but, seeing as you have allready done most of the work required to get access to what is potentially a very weak cell, why not just replace it now ?

-When in limited mode and lower battery voltage, the mV diff is 220mV

-Nissan wont resolve this, USA->EU means no warranty at all.
"Vehicles that have been sold in Europe have Pan-European warranty, this vehicle doesn't. Unfortunately we can't help you in this matter and offer goodwill."

- I might take you up on that, if I need a 2nd gen cell replacement if this balancing wont do

- Yeah, been charging it 6 times now, no visible change. The bypass shunts are minimal in the BMS, the nissaneleafforums said the process for solving imbalance can take 3-9months. I simply cannot wait for that long, especially since the cell might be bad! Let's see how it performs tonight and re-assess :)
 

Sean

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Oct 8, 2016
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The easy way to cut through the battery housing sealant is to use an oscillating saw, using both the half round, and straight blades - with one of these the two halves can be separated (thus giving full access to the cells) in about 20 minutes, which no damage or deformation to the casing. It's just RTV silicone, but use a good quality one when resealing.


image_rjrocc.jpg



Dala said:
-Nissan wont resolve this, USA->EU means no warranty at all.
"Vehicles that have been sold in Europe have Pan-European warranty, this vehicle doesn't. Unfortunately we can't help you in this matter and offer goodwill."

It'll not have the battery warming plates either ? You might want to try retrofitting them if you can find any, your climate will not be kind on the battery.

Are you intending to capacity check the cell before you reassemble ?
 

Dala

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Sean said:
The easy way to cut through the battery housing sealant is to use an oscillating saw, using both the half round, and straight blades - with one of these the two halves can be separated (thus giving full access to the cells) in about 20 minutes, which no damage or deformation to the casing. It's just RTV silicone, but use a good quality one when resealing.


It'll not have the battery warming plates either ? You might want to try retrofitting them if you can find any, your climate will not be kind on the battery.

Are you intending to capacity check the cell before you reassemble ?

Yeah thanks for the tip :) I unfortunately don't have any oscillating saws at my disposal, so basic knifes had to do the job. RTV silicone is just what I had in mind, since anything stronger like sikaflex would probably result in a practically welded shut case.

Also the warming plates, I thought about that, from what I've gathered, it's a 300W heating element for the batteries. I already have somethings that could be used as battery heaters, but I'm gonna focus on getting it running now first, and asses later on in winter how the range behaves.

No capacity check, if it sucks I'll replace it.
 

Sean

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Oct 8, 2016
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Out of interest, all of the packs I've disassembled have had some really badly applied seem sealant within the battery case, I assume Nissan are not confident that the case is fully weather proof - does yours have the same ?


image_vlauvt.jpg



image_vvouyv.jpg
 

Dala

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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! :D

image_zdgwat.jpg


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

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

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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... (Thanks Sean for pointing me in the right direction!)

Sean said:
Out of interest, all of the packs I've disassembled have had some really badly applied seem sealant within the battery case, I assume Nissan are not confident that the case is fully weather proof - does yours have the same ?

Yes, it had tons of goo all over the bottom and inside the case!
 

Sean

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If you buy an entire pack, you'll have enough cells for a wall, and to repair your EV.
 

Dala

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While waiting for emails on potential cells,

I decided to do my first mod! It's quite common in Finland to do grille blocks during winter, this allows the engine to heat up more rapidly and improve efficiency. But wait a minute, this is not an internal combustion car (ICE), so why do it to an EV?
-It improves aerodynamics, no air will be forced into the engine bay. Leaf owners swear by this mod, claiming 1-2% more efficient km/kWh at highway speeds

So here it is;

image_ggzqzb.jpg

I cut out some plexi, 70cm x 7cm, and attached it with zipties. I need all the extra range I can right now in this limited state :D
 

Dala

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After completing the rough balancing, the car can now go 85km instead of 25km. Still really bad, should be closer to 150km. So the troubleshooting continues.

I contacted a company that specializes in EVs, (EVs Enhanced), and they suggested doing a bottom balance instead of middle balance. This makes sense, since a balance in the middle of the State Of Charge(SOC) can be very imprecise. Making the cells bottom balanced will also help me in the future when I decide to swap the cell.

So here are the instructions for how to do a bottom balance:

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.

Let's get cracking!

Assume the service position after draining the battery.

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Remove the pack again. Charging 57&58 up to 3.8V, when the rest of the cells are at 3.7V

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Start discharging again with the unbalanced ones at top

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Interestingly, when the SOC number dissapears from the dash, the car still runs the heater for over an hour! The heater pulls ca 3kW

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After completing the true discharge, the diffs are growing rapidly at close to 0% SOC

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While waiting for all this charging and discharging, I started cleaning the car properly for the first time.
First thing to remove was the dealership stickers

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Much better

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Also waxed it for the first time

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I had also read threads about common issues. One of these was a faulty design in the shock absorber top mount, allowing water to pool on top of the bolt. This also affected this car and corrosion had started

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Dried it out and smeared some silicone sealant over it to make it waterproof. Very worthwile, some people even had reported failures here!

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So now I'm waiting for the pack to settle, and will continue with step 5&6 tomorrow.
 

Sean

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Very good :)

I'm off to collect a pair of complete 30kWh packs next week.
 

Dala

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Cool!

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.

image_lszglc.jpg


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.

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After driving it for 15km.

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After driving it for 30km

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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.
 

jdeadman

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Personally I'd pull that cell and replace it when it comes in. No amount of Balancing will cure low capacity on a cell.
 

Sean

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That pack has had a short, easy life - do you have access to a rapid(50kW) ?
 

Dala

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jdeadman said:
Personally I'd pull that cell and replace it when it comes in. No amount of Balancing will cure low capacity on a cell.

Ofcourse! This is just the extra legwork I decided to do, when the time comes to put in a new cell, I can just deplete the battery (thanks to my bottom balancing efforts) and slap in a new cell at <5% SOC. The extra time spent here helps further down the line.

Sean said:
That pack has had a short, easy life - do you have access to a rapid(50kW) ?

Loads of them floating around here, 3x CHAdeMO within 5km range of my flat! But I tend to stick to the free L1 chargers, might aswell save that 1 on each charge lol :p
 

Dala

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I just went 80km on a charge with heat on, then the low battery warning popped up. But all is not doom and gloom, I got my hands on a cell!


image_ekehim.jpg


It came from Italy, a company that specializes in conversions and home-brew scooter solutions. It was cheap, and SUPPOSEDLY low mileage.

Part number: 295B9-3NF0B QR 14520 07486

Before I just chuck this one in, it might be wise to capacity test it. Wouldn't be fun at all to put in the hours and end up with similar range.

Specs seem to point towards 0.3C discharge rate, so that's what I'll aim for. Only problem is, I only have 18650 capacity testers that are made for max 10AH batteries... Might be time to invest in some better testing equipment.
 

Dala

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So I've now driven 600km with the leaf, might give you guys a status update.

The charging situation is not ideal to say the least. Neither my apartment complex nor workplace wants to let me charge. So this leaves me with only public charging places (3x in my city) and the occasional visits to parents. Sometimes the public ones are temporarily unavailable (broken/occupied), so I am certainly paying the early adoptor tax. Not impossible to live with, but if you don't have home or workplace charging, I don't reccomend getting an electric car frankly.

So let's improve the situation. The Nissan branded charging cable that came with the car charges at a measly 8Amp. This roughly translates into 8km per hour added to the battery. This makes family visits long, since I need to spend ca 3-6h charging when visiting. Since that is way too much family time, I purchased the chinese Duosida 16A EVSE. It costs 200, so quite cheap! (Original Nissan charger costs 700!)

image_exwhpo.jpg


It works in exactly the same way as the stock one, but instead it draws 16Amps when charging. 16A is quite a lot from 240V AC, so you need to be careful where you plug this charger in, if it's a 10A outlet for instance you will trip the fuse. This cuts the charging time in half, so now I only need to spend 2-3h charging!

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I haven't had time to measure the capacity of the Italy cell, so I just put a small load on it to make it closer to 7V resting voltage, which is way better than the 8.2V it shipped with.

image_ytfxmw.jpg
 

Dala

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So Christmas came early, and the previous owner sent me an identical cell from the batch he used to 'fix' the car. It is from USA and has 30 written on it. If I were a betting man, I'd say that the 30 stands for 30Ah measured on one 4V cell. That would be a 33Ah->30Ah, 90.1% degraded cell, which makes sense. I will have to measure it myself to make sure. But at least now I can take a rough reference without taking the car out of service, and compare it against the Italian cell.

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What a complicated origin story, kudos if you are still following the thread :)

On a more interesting note, I did another tweak. I intend to switch all incandescent bulbs over to LED to save some electricity. The 10W license plate bulbs got swapped over to Osram 2W LEDs.

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Yellow incandescent on left (although my phone made it way whiter that it actually was), LED on the right

Doubt I actually get any more range with this mod, maybe half a meter more? :D
 

Sean

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I'll have a small quantity of cells available shortly if you aren't happy with the capacity of your new acquisition - from a rolled 2015 24 with just shy of 5k on it.
 

Dala

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Happy holidays! The Leaf is happily churning out spruces as I drive, very festive :)

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I am continuing the LED upgrade, here is the boot space lamp

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And here is the dome light. Both got 31mm wedge LEDs.

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I need all the range I can get now. When the cold hits this hard -12*C, the effective range falls down to 60km-ish. It is such a shame that I cannot prewarm it anywhere, if I could the range would be so much better. I noticed that if I prewarm it and charge right before leaving, the range is the same as autumn.

It is also quite hard to wash the car at -12, here is what happened when I started the pressure washer :p

image_txmfok.jpg


But after heating it in the garage, I could wash and wax it properly :)

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Oh, and this came in the mail. More on this later :)

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Sean said:
I'll have a small quantity of cells available shortly if you aren't happy with the capacity of your new acquisition - from a rolled 2015 24 with just shy of 5k on it.

Interesting, I will try to cap test and let you know as soon as possible!
 
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