Just Bought a Nissan Leaf With a Pretty Bad Battery

[Braddudya]

Just picked up a 2011 Nissan Leaf with 70K for $2700! It's in good shape inside and out and seems very mechanically sound. Only big problem I see is that it only gets about 35 miles per charge.

I live very close to where I work so 35 miles will get me to and from work for nearly a week. So it's a great buy as is but it would be great to extend the range. I've seen lots of people replace their batteries entirely but it's quite expensive. Is disassembling the battery and then testing each cell to replace the bad ones a crazy idea? I would guess the biggest issue would be that the cells will likely be mismatched.

Anyone have any suggestions?

Thanks

 

[JackFlorey]

Is disassembling the battery and then testing each cell to replace the bad ones a crazy idea?

Not that crazy. Get a CAN bus analyzer so you can check out what the cell voltages are. If a few are very low near the end of discharge, it might be worth seeing if they are fixable. If, for example, four battery modules (eight cells) are causing the limitation, replacing those might significantly improve your range.

The 2011 Leafs used modular metal-cased batteries so it's fairly easy to work on them. If you go this route, observe all high voltage electrical precautions (insulated gloves, insulated tools) and maue sure that the new cells are the same voltage as the existing cells before you replace them (to make the balancer's job easier.)

 

[Braddudya]

Is disassembling the battery and then testing each cell to replace the bad ones a crazy idea?

Not that crazy. Get a CAN bus analyzer so you can check out what the cell voltages are. If a few are very low near the end of discharge, it might be worth seeing if they are fixable. If, for example, four battery modules (eight cells) are causing the limitation, replacing those might significantly improve your range.

The 2011 Leafs used modular metal-cased batteries so it's fairly easy to work on them. If you go this route, observe all high voltage electrical precautions (insulated gloves, insulated tools) and maue sure that the new cells are the same voltage as the existing cells before you replace them (to make the balancer's job easier.)

This is what I envisioned as the single cells seem quite available online. I guess I don't need to worry too much about mismatched capacity as they are likely way matched right now with a number of bad cells.

Will the can bus analyzer let you see the cells without dropping the battery? Essentially I am asking if you know where you splice or plug in to get a reading? Seems like the best place to start. Thank you.

 

[ynot]

I bought a Leaf Battery last year, I wanted the modules so I disassembled the battery pack. It is not a trivial undertaking. For me the modules have been great, use them in my etractor, and in my freighter trike.
If you try to replace modules you are going to have to keep track of the balance wires and there are a lot of them, You will not be able to pull one or two modules out because they are in packs that are bolted together and have bus bars bolted to each module. There are lots of parts that will have to be removed and then replaced. I happened to have a pair of lineman's gloves which I wore, once you have the big orange cables off you are pretty safe, but you have to be really careful not to short out a module or pack with a wrench. I managed to short one module and before it blew a fuse, it had burned a hole in the modules case. The potential energy available is quite large.
My guess is that it will take at least 80 hours of very focussed work to pull the battery apart and put it back together.

 

[Braddudya]

I bought a Leaf Battery last year, I wanted the modules so I disassembled the battery pack. It is not a trivial undertaking. For me the modules have been great, use them in my etractor, and in my freighter trike.
If you try to replace modules you are going to have to keep track of the balance wires and there are a lot of them, You will not be able to pull one or two modules out because they are in packs that are bolted together and have bus bars bolted to each module. There are lots of parts that will have to be removed and then replaced. I happened to have a pair of lineman's gloves which I wore, once you have the big orange cables off you are pretty safe, but you have to be really careful not to short out a module or pack with a wrench. I managed to short one module and before it blew a fuse, it had burned a hole in the modules case. The potential energy available is quite large.
My guess is that it will take at least 80 hours of very focussed work to pull the battery apart and put it back together.

That is less encouraging haha.

I am aware that the potential energy in the battery is immense! I would buy the proper tools to minimize the risk but it would be risky none the less. 80 hours though is an awful lot. Makes the $5000 used battery look quite a bit better. I will have to look more into pack dissembly and make sure I want to go that far.

You didn't happen to document the process did you?

 

[whereswally606]

i have a 2011 leaf the battery is pretty bad but it is propped up by a muxsan 17.6kwh pack made from vw gte hybrid packs.

Few things to be careful of in the 2011 (or rather sub 2013). There is a software issue that can cause a fail dangerous/stupid state. If you have a low 12v battery in winter (or whenever) the car can get into a state where the contactor for the precharge resistor stays in circuit and then blows. this lives in the traction battery pack in black case at the front underneath. Its a pain to change and I've since externalised mine so that if it ever happens again i can get going at the roadside without having to tow a dead ev to a garage with a lift.

Batteries wise the 2011 canary packs are pretty shit, you would be much better off getting a canbridge from dala EV or using leaf spy pro to match a better 2nd gen pack 2013 onward.

Otherwise other cheap mods are aero wheels inserts printed, airdam printed or made by hand in winter, do the strut covers for the suspension tops at the front as water collects there. sack of using the heater ever and buy some 12v heated seat pads and run off a separate 12v source. you can hack in a diesel heater into the cars heater pipes in the 2011 though. also get yourself a 12v lipo jumpstarter they are very useful when your 12v battery starts to misbehave.
hope all this helps. good luck

 

[ynot]

I bought a Leaf Battery last year, My guess is that it will take at least 80 hours of very focussed work to pull the battery apart and put it back together.

That is less encouraging haha.

I am aware that the potential energy in the battery is immense! I would buy the proper tools to minimize the risk but it would be risky none the less. 80 hours though is an awful lot. Makes the $5000 used battery look quite a bit better. I will have to look more into pack dissembly and make sure I want to go that far.



You didn't happen to document the process did you?

There are a number of youtube vids on dissasembling the battery but never found one that described swapping modules. If you go to all that work, you will have to be certain that the modules you buy are worthy of all the work to install.
Be prepared to handle a 650 lb battery, you might find it easier to unbolt the battery then lift the car off it.
Personally I would not tackle the job, but if you are younger, have the time, and have a good feel for pulling wrenches and sorting our wires, and meticulous testing, I wish you well

 

[JackFlorey]

Will the can bus analyzer let you see the cells without dropping the battery? Essentially I am asking if you know where you splice or plug in to get a reading? Seems like the best place to start.

With just the CAN bus analyzer you can get cell voltages. You have to request them and then they are sent in an encoded format. (Alternatively just watch that bus in a powered-on Leaf with an analyzer.) There are plenty of websites that show you how to decode them.

https://www.mynissanleaf.com/viewtopic.php?t=11676

 

[Braddudya]

Thanks all for the advice.

The leaf only has 70K miles and I only paid $2700 for it so for now I am just going to use it for my daily commute. I am hesitant to invest in a full battery swap mainly because it is not a fast charging version so it will essentially always a be a charge at work or home car.

For now I can charge it at work for free and avoid the $5.50 a gallon gas here in Reno! I'm sure it will be $10 before year end so I am happy with that!

As for not doing more damage...what state of charge should I generally try to keep it in? Is it bad the charge it "full" even though it only ever reads like half bars no matter how long it charges? I am familiar how to treat healthy batteries but I have never tried to keep a weak battery going for as long as possible.

 

[Braddudya]

I have looked further into actual battery module replacement and frankly it doesn't seem too bad.

The keys seem to be:
1. Find a lift and lift the car off the battery
2. Use Leaf Spy to search for the bad cells
3. Make sure voltages match before reassembly

Otherwise it doesn't look like it requires any special tools. And in one video they reported it only took a few hours in total to drop the battery, diagnose, replace the cell, and reinstall the battery. Of course it wasn't their first time but still it doesn't seem too bad.

Obviously it's still not going to be a high capacity battery or a battery that will last another 10 years BUT it should only cost a couple hundred bucks to potentially double my range!

Obviously the main concern is safety but again it doesn't seem that bad as long as you take take your time and plan it out.

 

[Braddudya]

I got leaf Spy fired up and played around with it a bit. Very interesting tool.

I am trying to see if there are some obvious bad cells. The problem is that the BMS will essentially hide the bad cells right? How do I go about determining which cells have the least capacity while the BMS is actively balancing in an attempt to erase this difference?

 

[larsb]

How good data can you get out of the car? Does it report or even better log at the cell level? If you have some weaker cells in the pack their voltage will dive a bit deeper under load than the others (relatively deeper.. don’t know how hard a leaf loads its’ cells) and if the bms logs cell capacity then this will also show. I guess this is the best scenario. If pack is more evenly worn then you wouldn’t really see it and the big improvements by switching a few cells isn’t there.

 

[Braddudya]

How good data can you get out of the car? Does it report or even better log at the cell level? If you have some weaker cells in the pack their voltage will dive a bit deeper under load than the others (relatively deeper.. don’t know how hard a leaf loads its’ cells) and if the bms logs cell capacity then this will also show. I guess this is the best scenario. If pack is more evenly worn then you wouldn’t really see it and the big improvements by switching a few cells isn’t there.

It reports at cell level or "module level" since each module is actually 2S. I don't know about logging. I will have to play with it. I've been out of town at a trade show and now I have COVID so I have only been able to fire it up the one time!

 

[john61ct]

I would consider paying for an official full pack swap.

Low mileage otherwise, and your investment so far is so minimal...

 

[Braddudya]

I would consider paying for an official full pack swap.

Low mileage otherwise, and your investment so far is so minimal...

Yeah I've had the same thought. The problem is that even the newer batteries have similar issues in terms of longevity. $6-8k (not including interstate transport to a shop that does it) is a lot to drop on a car with such bad resale. Its also just a matter of time before the new battery is dropping capacity significantly as well.

For now I will probably just use it. Maybe some day with some more research and experience I will try going LiFePO4 or something fun and more durable. I don't think these old batteries are famous for their energy density so it might be possible to build an LiFePO4 with similar capacity and in the factory battery box...maybe haha

 

[JackFlorey]

This is what I envisioned as the single cells seem quite available online. I guess I don't need to worry too much about mismatched capacity as they are likely way matched right now with a number of bad cells.

I assume you mean "not matched."

Will the can bus analyzer let you see the cells without dropping the battery?

Yes, but once you open up the battery it's pretty trivial to measure cell voltages directly. And you have to do that anyway.

 

[marcexec]

Check out "Dala's EV Repair" on Youtube. He also sells a CAN bus bridge that allows you to swap to a complete new battery (if you can find one) and pair it with your car. Much easier than messing with the sealed pack for a marginal upgrade (IMO). See if you can source a 2018+ 40kWh pack and imagine what that would do for the usability of your car

 

[Braddudya]

As an update I sold that car and bought another 2012 one with better (45 miles or so) range for even cheaper that was "broken" aka needed a fresh 12v for $90 at costco! No matter how I crunch the numbers it just isn't worth doing any sort of upgrade to get more range. For now I still daily the new car and really enjoy it.

Current plan is to daily it until something goes wrong or it gets ridiculous low range and then use it for some sort of crazy project. I'm thinking electric RZR or just kart it out and do custom high drain battery with a completely new performance controller. It seems like the prices for high power controllers drops a lot every year so I think in a few years this could be a fun and fairly affordable project. These first gen motors are overbuilt and easily capable of 300hp for short durations based on what I have read. That should be plenty of fun.