Any thoughts on extending the life of used Nissan Leaf batteries ?

[Ampster]

................

THAT is why I harp so much on using batteries with a known state beforehand. One just doesn't know if sudden death is awaiting from abuse (which can also involve mechanical shock) etc etc.

Doing a "one-off" goof can be pulled off - but there is nothing to learn if hidden internal problems, which can be just 10 cycles away, are laying in wait.

Good advice. As I mentioned I purchased these two years ago. I view them as sunk costs but buying more is another issue. This thread has helped me evaluate a capacity increase. I think I am going to put that off for as long as I can and save up for new CALBs or equivalent. I may look at adding 9 panels to the Skybox first. Currently the Skybox has no panels and I have the roof space. I will have to do some number crunching over the next six months once I finally get on my NEM agreement.

[PNjunction]

I've experienced sudden death of cells. Mostly from over-discharge down to zero volts. Although I have been able to revive them with very low current recharging techniques done very soon after noticing the event, and even obtained what seemed like near perfect capacity recovery, there is a surprise waiting:

When li-ion (be it lfp or otherwise) is taken below say 2.5v per cell, what starts to happen is the SEI layer starts to dissolve and contaminate the electrolyte.

Think of the SEI layer as an automotive oil filter. You need it to prevent an engine from failing rapidly. However, if it gets clogged with junk, what was once protecting the engine, is now starving it, and the engine fails.

In this case of over-discharge, you have basically melted the filter and all the contaminants into the oil.

Putting a new filter in, (saving the over-discharged cell with very low current revival techniques if done in time), *SEEMS* to revive the cell, as a new SEI layer is created. But the electrolyte in the case of the battery is still contaminated with a special surprise waiting.

Those contaminants are fertile ground for dendrite growth and higher-impedance as time goes on, and the normal growth of the *new* sei layer laid down with recovery grows faster than usual, since the contaminants are in the electrolyte.

The sudden death is that even though there is plenty of active material available, you can't get to it - the lithium can't intercalate through that clogged sei layer that grew faster than usual. It will do it's best, but like a light switch, all of the last remaining pores to intercalate through are closed.

THAT is why I harp so much on using batteries with a known state beforehand. One just doesn't know if sudden death is awaiting from abuse (which can also involve mechanical shock) etc etc.

Doing a "one-off" goof can be pulled off - but there is nothing to learn if hidden internal problems, which can be just 10 cycles away, are laying in wait.

[Ampster]

........ There is a DIY Electric Car Forum that is all about Lithium and especially Nissan batteries.......

Been there since 2012. Basically the same information that has been repeated here. Probably the best overall information in one spot is the sticky by PNjunction

My cells are at 70% of original capacity and that is what they were at when I bought them two and a half years ago. I used them with a Radian inverter for two years and was charging them to 4.15v per cell and rarely ran them down to 3.75v. I am keeping a eye out for that "sudden death" syndrome.

[Sunking]

Doesn't Nissan sell replacement batteries for the Leaf or is that only a Dealer option item?

New packs, not cells, are only sold by dealers. Only way for Joe Public to obtain Leaf Batteries is salvage. Same for any EV. Only reason Nissan even makes new batteries available is because Uncle Sam makes them and to stay out of bankruptcy court with warranty claims.

[Sunking]

The talk that I would like get from others is how to extend the life of Nissan Leaf cells.

Again Stupid Simple and you keep making it complicated when it is very simple. Never charge them to more than 90% SOC, and never discharge them below 10% DOD. In addition never allow them to go below 32 degrees or above 100 degrees. Stupid Simple enough. That is what EV manufactures do and the only reason they can offer any kind of warranty on the battery. Otherwise they are toast after 300 to 500 cycles.

However you are not going to get detailed information on a DIY forum, It is well beyond the scope and liability limits. One misinterpretation, what question you do not know to ask, and you could injure or kill yourself, and then your survivors sue the forum due to your ignorance. You want the real dope, go to a professional forum where you will not be allowed to ask any questions. Pros are not going to write pages of text to educate you, that is why they went to school of 4 to 12 years and charge $300/hour to work for you.

Here is the best tip you are going to get on this forum to get help. LEAVE. There is a DIY Electric Car Forum that is all about Lithium and especially Nissan batteries. But be warned most ar eprofessionals and wil not hold your hand for long. Folks like Nebster are not tolerated there, and banned real quick before being BBQ'ed publically. Lot of pros there and the DIY;s are from the electrical industry with a lot of experience and education. You will thank me later.

[SunEagle]

Maybe this will help in regards to Leaf batteries (and other chemistries as well). Have you seen this classic video from Prof Jeffrey Dahn?

https://www.youtube.com/watch?v=pxP0Cu00sZs

The point to all of this is to simply run your batteries in a cool environment. Stay within the margins. If you do need to go full charge or full discharge, limit your time doing so.

The one thing you don't know about used leaf cells is when you *may* be facing the "sudden death" syndrome, (usually massive SEI layer buildup) where prior abuse, undetectable by the user, turns the cell off completely.

For your project, I suggest you buy a brand-new Leaf, and use cells from that. Sell the chassis to someone else.

Doesn't Nissan sell replacement batteries for the Leaf or is that only a Dealer option item?

[PNjunction]

Maybe this will help in regards to Leaf batteries (and other chemistries as well). Have you seen this classic video from Prof Jeffrey Dahn?

https://www.youtube.com/watch?v=pxP0Cu00sZs

The point to all of this is to simply run your batteries in a cool environment. Stay within the margins. If you do need to go full charge or full discharge, limit your time doing so.

The one thing you don't know about used leaf cells is when you *may* be facing the "sudden death" syndrome, (usually massive SEI layer buildup) where prior abuse, undetectable by the user, turns the cell off completely.

For your project, I suggest you buy a brand-new Leaf, and use cells from that. Sell the chassis to someone else.

[PNjunction]

Familiar with Winston and Calbs myself. Moreso the GBS large format LFP prismatics. Posted much about them here.

Thing is, despite the Leaf cells not being the 3.2v nominal LFP chemistry, there are basics that you should already know by now to answer your own question.

Don't run them in hot temps.

Try not to run below 20% capacity, nor charge beyond 80% capacity. That capacity will have to be measured as the cells age, and ALSO adjust your charge current accordingly. Typically spec'ed at 0.3C for most efficiency. This would of course be an adaptive charge strategy.

Or, for the most life, run them at only + / - five percent of their *measured* capacity, centering in the middle. Not practical.

Man, this is just a boring rehash of the days when guys would try to diy off-grid setups from used / abused / counterfeit A123 LFP cells pulled from garage tool packs, and solicit the same kind of "discussions" on how to extend the life of their trash.

You know better than this - I just can't figure out the real angle. At least that is how your responses come across.

[Ampster]

Most cell phone batteries seem to lose their ability to hold a full charge after a couple of years being used. Maybe the Leaf batteries are better.

Yes, I don't expect to abuse them like I do my cell phone. I also expect to excercise more control over the charging and discharging of these cells.

What ever the result of those used cells I would suggest you keep very good records of each discharge/charge if that is even possible considering the lack of an SOC measuring device that is 100% accurate.

Good advice. So far I am manually tracking kWhrs in and kWhrs out. I am hoping that when I get my BMS configured that it will do that as well as keep a log. I had an issue in the past that the current shunt on the BMS was not accurate because the Radian inverter threw off too much EMF. I can only get kWhrs discharged from my Skybox since I am not using the internal charger.

[Ampster]

The more practical question is are you skilled enough to disassemble these packs without damaging the cells further and be safe about it?

Are you skilled enough to measure capacity and internal resistance and match up these used cells into a properly performing battery? Or are we talking watching videos using speaker wire jumpers, hot soldering blobs etc as a diy project?

Many previous discussions like this juggling numbers about using damaged / trash cells just go nowhere after all the talk and no walk. We do all the homework, and nothing comes of it except for filling up forum server storage.

The real catch-22 irony about it is if you have to ask how to do it, then you don't have the knowledge or safety skill to do it right. A one-off piece of junk - maybe.

Those are good rhetorical questions that any one who is proposing to do this should ask themselves.

A Nissan pack consists of modules that fully enclose the cells. I would not suggest than anyone open up those modules. I use a PL6 to measure the capacity of the parallel cells within the modules. The modules are bolted together in parallel groups of 6. I use copper busbars sized to carry the 100 Amps max load that the Inverter could draw. I use an inline fuse rated at 100Amps. I have been configuring large format LFP batteries (Voltonics, Winston and CALB) into packs for my own use in EVs and Energy storage for the past 6 years. I bought these particular modules two years ago and used them to run a Outback Radian hybrid inverter that I had installed for load shifting and backup. I sold that inverter when I rented that house and moved to my current home. Those modules are currently running an Outback Skybox providing the same load shifting and back up that the Radian provided. That is the walk that I have done.

The talk that I would like get from others is how to extend the life of Nissan Leaf cells. That is the subject of this thread. So far not much information on that topic has been offered other than used cells are a gamble. That is a gamble that I knowingly took when I bought that pack two years ago. I am still waiting for someone to share more knowledge on the topic. I know that Sunking has had some experience with these modules and I have searched this thread and found a few snippets of knowledge.
My hope is that if there is additional knowledge and if it is shared, then this thread may provide useful information for others on how to extend the life of Nissan Leaf cells when used for energy storage.

[PNjunction]

The more practical question is are you skilled enough to disassemble these packs without damaging the cells further and be safe about it?

Are you skilled enough to measure capacity and internal resistance and match up these used cells into a properly performing battery? Or are we talking watching videos using speaker wire jumpers, hot soldering blobs etc as a diy project?

Many previous discussions like this juggling numbers about using damaged / trash cells just go nowhere after all the talk and no walk. We do all the homework, and nothing comes of it except for filling up forum server storage.

The real catch-22 irony about it is if you have to ask how to do it, then you don't have the knowledge or safety skill to do it right. A one-off piece of junk - maybe.

[SunEagle]

Yes, that is my hypothesis.

Yes, the operative word is IF, and that of course is the issue that I am trying to explore. Sunking has said that after 80% degradation the capacity of Leaf cells drop off as fast as a man goes senile after 60 years of age. That doesn't give me much to go on. The slope of that line in quantifiable terms would shed some light on this issue. Some of us are above that age by a significant number of years so I guess the old saying may hold true, your mileage may vary. Hope springs eternal and I am hopeful that I will be cognizant in 5 years to see the result of this experiment. My initial costs for these Nissan Leaf cells are sunk costs. The real decision will come in a year or two when I determine how much more storage I need.

Yes, and in this rapidly moving market so I am not sure I have any confidence in a company like SimplipPhi being around in 10 years so that is why I am not taking that gamble.
The chemistry has been around for more than 20 years and certainly the experience in our phones and laptops would not suggest much beyond 2 or 3 years.

Most cell phone batteries seem to lose their ability to hold a full charge after a couple of years being used. Maybe the Leaf batteries are better.

What ever the result of those used cells I would suggest you keep very good records of each discharge/charge if that is even possible considering the lack of an SOC measuring device that is 100% accurate.

[Ampster]

I guess the Leaf battery's life could depend on both the DOD% as well as the number of cycles.

Yes, that is my hypothesis.

If you can get 50% output for 5 years then it would be worth the investment at $0.11/kWh. I guess the problem is can you still get 50% DOD each day after 3 years or will it be reduced due to battery age.

Yes, the operative word is IF, and that of course is the issue that I am trying to explore. Sunking has said that after 80% degradation the capacity of Leaf cells drop off as fast as a man goes senile after 60 years of age. That doesn't give me much to go on. The slope of that line in quantifiable terms would shed some light on this issue. Some of us are above that age by a significant number of years so I guess the old saying may hold true, your mileage may vary. Hope springs eternal and I am hopeful that I will be cognizant in 5 years to see the result of this experiment. My initial costs for these Nissan Leaf cells are sunk costs. The real decision will come in a year or two when I determine how much more storage I need.

Due to the limited usage of this chemistry I still do not trust an Li battery to last 10 years even if it is guaranteed.

Yes, and in this rapidly moving market so I am not sure I have any confidence in a company like SimplipPhi being around in 10 years so that is why I am not taking that gamble.
The chemistry has been around for more than 20 years but certainly experience in our phones and laptops would not suggest much beyond 2 or 3 years. There are some examples in EVs of a much longer life but Nissan has not been one of them in a motive application.

[SunEagle]

Perhaps my statement did not include the correct qualifiers. My initial cost for the used Nissan leaf pack was $100 per kWhr using that assumption I assumed I could get 5 years and that I would use 50% of their capacity each day. That would give me 900kWhs over the assumed life. The math is .5kWh times 360 days times 5 years. That works out to be a cost per kWhr of $0.11 over the life of those batteries. Clearly those assumptions are critical. If I cannot get the expected life my cost goes up. That is the gamble I take. I am not sure I can acquire more Leaf modules at even $200 per usable kWh and any expansion of my pack would have to take that into consideration as well as what I determine the probability of even getting 5 years out of them.

Another option is new CALBs. If I assume a cost of $450 per kWh and a life of 10 years then the lifetime cost of that investment is $0.25/kWh. On the other hand a SimpliPhi would be about $900/kWh with a total cost $0.50 per kWh over the guaranteed life of 10 years. I use the SimpliPhi as an example because it has a guaranteed life of 10 years. Everything else is a gamble.

The point of this post is not to debate the assumptions, rather to explore ways to manage the use of Lithium batteries to extend the life. Obviously if I only got 5 years out of the CALBs then the cost is the same as the SimpliPhi.
Also the topic of FLA or AGM vs Lithium has already been debated and I am not interested in reviving that debate.

I guess the Leaf battery's life could depend on both the DOD% as well as the number of cycles.

If you can get 50% output for 5 years then it would be worth the investment at $0.11/kWh. I guess the problem is can you still get 50% DOD each day after 3 years or will it be reduced due to battery age.

Due to the limited usage of this chemistry I still do not trust an Li battery to last 10 years even if it is guaranteed.

[Ampster]

I'd like to see your numbers, logic and justification for the statement that they are a cost effective alternative to new batteries. Seems to me that broad claims need backup.

Perhaps my statement did not include the correct qualifiers. My initial cost for the used Nissan leaf pack was $100 per kWhr using that assumption I assumed I could get 5 years and that I would use 50% of their capacity each day. That would give me 900kWhs over the assumed life. The math is .5kWh/day times 360 days times 5 years. That works out to be a cost per kWhr of $0.11 over the life of those batteries. Clearly those assumptions are critical. If I cannot get the expected life my cost goes up. That is the gamble I take. I am not sure I can acquire more Leaf modules at even $200 per usable kWh and any expansion of my pack would have to take that into consideration as well as what I determine the probability of even getting 5 years out of them. That is what I hope to get out of this discussion.

One of the options I used for comparative purposes is new CALBs. If I assume a cost of $450 per kWh and a life of 10 years then the lifetime cost of that investment is $0.25/kWh. On the other hand a SimpliPhi would be about $900/kWh with a total cost $0.50 per kWh over the guaranteed life of 10 years. I use the SimpliPhi as an example because it has a guaranteed life of 10 years. As SunEagle said, used batteries are a gamble and getting 10 years out of CALBs may be also be a gamble.

The point of this post is not to debate the assumptions, rather to explore ways to manage the use of Lithium batteries to extend their life. Obviously if I only got 5 years out of the CALBs then the cost is the same as the SimpliPhi.
Also the topic of FLA or AGM vs Lithium has already been debated and I am not interested in reviving that debate.