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Discussion Starter #1
First, I'd like to apologize for creating a thread on a technology that there are many such threads in this forum. I have certain questions regarding these cells for a solar build and you all seem to have as good a grasp on them as anywhere else I've come across. I'm just diving into learning about battery technology, so please excuse my ignorance and/or poor vocabulary on the subject. I've done a lot of reading of various threads in this forum, and while a lot of the technical talk flies straight over my head, in general it's been fairly informative. So, if I may, make some statements that I think are true of the battery/bms (along with questions), and if I'm off, could someone be so kind to point me in the right direction?

  • The on-board BMS does not have balancing functionality at this time (is this just a matter of time and figuring out, or is there a good chance that external BMSs would be needed for a solar setup?)
  • Greentec auto has seemed to be a good vendor for these cells and most testing has shown that the vast majority of cells perform as expected.
  • These cells came from the Honda Fit which has been around for under a decade. (If I were to buy 36 24 cell blocks, would there be much of a risk of having wildly different battery cell quality based on how the previous owner drove and treated their vehicle?)
  • If I wanted to use the on-board BMS, I'd need to have individual IDs for each string of 18 batteries. (What does that mean exactly for a solar setup?)
  • If the on-board BMS does not work for my setup, I'd either have to unseries the 12 cell packs by cutting the tabs between each cell and use a single BMS, or use a separate BMS for each series of cells which would be 36 separate BMS in my case. (how much work and know-how would go into either option?)
  • The voltage is odd for inverters and chargers but not impossible to find components without cutting cells out.
  • These are safe to use but a over-charging could seriously damage the cells. (any options to handle this without a BMS?)
That's all I have at the top of my head. Thanks so much for any help anyone is willing to provide.
 

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You are going to have to do the leg work yourself i'm afraid.
It's all on here already scattered around.
I appreciate you might be new to the game, so sorry about that.
If you haven't got the backgorund knowledge and technical skills you are in for a struggle.

If you want personal assistance PM me..
 

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Discussion Starter #3
You are going to have to do the leg work yourself i'm afraid.
It's all on here already scattered around.
I appreciate you might be new to the game, so sorry about that.
If you haven't got the backgorund knowledge and technical skills you are in for a struggle.

If you want personal assistance PM me..
Right on. I appreciate the offer for assistance.
 

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I think that I have done the only broad based testing of the packs. Ian did some detailed testing on self discharge which is well documented. Both his and my results are summarized in this thread:


The thread is a good read if you are interested in performance details, though the early part of the thread does a lot of side discussion trying to get my PL8 operational.

The testing was done with a Revolectronix PL8, which allows balanced charging. Member IamIan is the expert on the PL8, which is a pretty sophisticated charger.

This is the list of InsightCentral members who have actually completed LTO conversions to the Gen1 Insight:


You can count up the total of deployed packs. It is substantial. To my knowledge, there have been 2 cell failures, which of course impact 2 pacts since the packs cannot be easily repaired.

Most of my testing has been done at a derated range of 2-2.5V. The capacity at that voltage range measures about 16.5Ahr +/- a bit.

I have recently tested 4 packs at 1.5-2.7V, the spec operating range. Those tests show capacity of about 19.7 Ahr +/-, though the PL8 almost always shut off short of 1.5V when the weakest cell dropped to that level.

All-in-all the Fit LTO packs are pretty darn good. If you are considering a solar battery with that many packs, you may as well buy a PL8 and do your own testing and remove the guessing ;)
 

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Discussion Starter #6
I think that I have done the only broad based testing of the packs. Ian did some detailed testing on self discharge which is well documented. Both his and my results are summarized in this thread:


The thread is a good read if you are interested in performance details, though the early part of the thread does a lot of side discussion trying to get my PL8 operational.

The testing was done with a Revolectronix PL8, which allows balanced charging. Member IamIan is the expert on the PL8, which is a pretty sophisticated charger.

This is the list of InsightCentral members who have actually completed LTO conversions to the Gen1 Insight:


You can count up the total of deployed packs. It is substantial. To my knowledge, there have been 2 cell failures, which of course impact 2 pacts since the packs cannot be easily repaired.

Most of my testing has been done at a derated range of 2-2.5V. The capacity at that voltage range measures about 16.5Ahr +/- a bit.

I have recently tested 4 packs at 1.5-2.7V, the spec operating range. Those tests show capacity of about 19.7 Ahr +/-, though the PL8 almost always shut off short of 1.5V when the weakest cell dropped to that level.

All-in-all the Fit LTO packs are pretty darn good. If you are considering a solar battery with that many packs, you may as well buy a PL8 and do your own testing and remove the guessing ;)
Ahhhh, thank you! I saw a lot of posts about PL8 around here and thought maybe it was a car thing.

This may be a totally stupid question, but I’m taking it that Toshiba has a proprietary software or set of commands to run the BMS. Has anyone been able to communicate with them about purchasing the software/instructions or would a mechanic/dealership that works on EV be able to obtain that info?
 

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First, I'd like to apologize for creating a thread on a technology that there are many such threads in this forum. I have certain questions regarding these cells for a solar build and you all seem to have as good a grasp on them as anywhere else I've come across. I'm just diving into learning about battery technology, so please excuse my ignorance and/or poor vocabulary on the subject. I've done a lot of reading of various threads in this forum, and while a lot of the technical talk flies straight over my head, in general it's been fairly informative. So, if I may, make some statements that I think are true of the battery/bms (along with questions), and if I'm off, could someone be so kind to point me in the right direction?

  • The on-board BMS does not have balancing functionality at this time (is this just a matter of time and figuring out, or is there a good chance that external BMSs would be needed for a solar setup?)
  • Greentec auto has seemed to be a good vendor for these cells and most testing has shown that the vast majority of cells perform as expected.
  • These cells came from the Honda Fit which has been around for under a decade. (If I were to buy 36 24 cell blocks, would there be much of a risk of having wildly different battery cell quality based on how the previous owner drove and treated their vehicle?)
  • If I wanted to use the on-board BMS, I'd need to have individual IDs for each string of 18 batteries. (What does that mean exactly for a solar setup?)
  • If the on-board BMS does not work for my setup, I'd either have to unseries the 12 cell packs by cutting the tabs between each cell and use a single BMS, or use a separate BMS for each series of cells which would be 36 separate BMS in my case. (how much work and know-how would go into either option?)
  • The voltage is odd for inverters and chargers but not impossible to find components without cutting cells out.
  • These are safe to use but a over-charging could seriously damage the cells. (any options to handle this without a BMS?)
That's all I have at the top of my head. Thanks so much for any help anyone is willing to provide.
The on-board bms hasn't been reversed engineered for balancing at this time. Even if someone cracks it in the future though be aware this is a car style bms that expects to be powered from a 12V battery on the side not the pack itself like solar bms's do.

The cells I've purchased vary a bit but capacity seems mostly there from new (85% at a minimum). The fit was pretty much a 3 year lease maximum so assuming a daily charge due to the limited range on the high end they should have been cycled around 1000 times. Certain drivers could certainly have done much less if it was only used sparingly but no way to know.

There is a ton of work involved in getting the cells for parallel and not series. There is a seperate thread of someone doing it recently that has more info but just be aware it take a lot of time. Splitting the 24 into 2 packs of 12 is easy but splitting off into individual cells is not easy at all.

Voltage is not ideal for regular inverters. For 12V it's between 5S and 6S. For 24V 11S is pretty spot on and for 48V 22S is good. To align this with the packs of 12 though means either wasting a cell or going through all the work to split the individual cells. For 24V and 48V there are some that would handle 12S or 24S though like the MPP solar LV-MK line. They're a bit more expensive than their base line but can go up to a high DC cut off of 32V or 64V respectively which would get basically the whole range LTO has to offer.

The cells usually don't drift much but with that large of a pack it's best to not mess around you should have a bms. That many bms's is cost prohibitive so you would want to parallel first and then just have the single bms on the parallel packs. I don't think splitting that many cells is worth the effort for the parallel portion, it'd be easier to just wire it up to a fuse block used in reverse strapped to the pack.
 

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This may be a totally stupid question, but I’m taking it that Toshiba has a proprietary software or set of commands to run the BMS. Has anyone been able to communicate with them about purchasing the software/instructions or would a mechanic/dealership that works on EV be able to obtain that info?
You would be right, but you need to do some reading own your own. Try typing "LTO BMS" into the search engine above. You will find lots of good info there. Member retepsnikrep has been able to break enough of the code to read the individual BMS board IDs, and read the individual cell voltages. He has not yet figured out how to activate the balancing function. But search the archives as directed and do some reading;)
 

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Discussion Starter #9
The on-board bms hasn't been reversed engineered for balancing at this time. Even if someone cracks it in the future though be aware this is a car style bms that expects to be powered from a 12V battery on the side not the pack itself like solar bms's do.

The cells I've purchased vary a bit but capacity seems mostly there from new (85% at a minimum). The fit was pretty much a 3 year lease maximum so assuming a daily charge due to the limited range on the high end they should have been cycled around 1000 times. Certain drivers could certainly have done much less if it was only used sparingly but no way to know.

There is a ton of work involved in getting the cells for parallel and not series. There is a seperate thread of someone doing it recently that has more info but just be aware it take a lot of time. Splitting the 24 into 2 packs of 12 is easy but splitting off into individual cells is not easy at all.

Voltage is not ideal for regular inverters. For 12V it's between 5S and 6S. For 24V 11S is pretty spot on and for 48V 22S is good. To align this with the packs of 12 though means either wasting a cell or going through all the work to split the individual cells. For 24V and 48V there are some that would handle 12S or 24S though like the MPP solar LV-MK line. They're a bit more expensive than their base line but can go up to a high DC cut off of 32V or 64V respectively which would get basically the whole range LTO has to offer.

The cells usually don't drift much but with that large of a pack it's best to not mess around you should have a bms. That many bms's is cost prohibitive so you would want to parallel first and then just have the single bms on the parallel packs. I don't think splitting that many cells is worth the effort for the parallel portion, it'd be easier to just wire it up to a fuse block used in reverse strapped to the pack.
Wow, thanks for all that info.

So I watched a video from David Poz where he got 4 BMS from a company in China for $45/each total cost. This would amount to an additional $1600+ to my setup. Certainly a large sum, but when considering the total cost of a complete solar system run on LTO tech, it's not too crazy. If I were to build from scratch with new Yinlong batteries, the cost of the battery bank would cost nearly 40k, so adding $1600 onto the SCiB cells, while annoying, is not necessarily cost prohibitive for me. Still, I'd like to avoid spending too much.

"it'd be easier to just wire it up to a fuse block used in reverse strapped to the pack."

What exactly does this mean?
 

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Wow, thanks for all that info.

So I watched a video from David Poz where he got 4 BMS from a company in China for $45/each total cost. This would amount to an additional $1600+ to my setup. Certainly a large sum, but when considering the total cost of a complete solar system run on LTO tech, it's not too crazy. If I were to build from scratch with new Yinlong batteries, the cost of the battery bank would cost nearly 40k, so adding $1600 onto the SCiB cells, while annoying, is not necessarily cost prohibitive for me. Still, I'd like to avoid spending too much.

"it'd be easier to just wire it up to a fuse block used in reverse strapped to the pack."

What exactly does this mean?
I don't think those were LTO bms's, if they were send me a link. Most solar bms's balance on the high end when it hits a certain voltage. With li-ion and lifepo4 dominating the market almost all bms's start to balance in the high 3 or low 4 volt range. LTO is charged at 2.7 volts and this never hits the threshold so those bms's would never balance. There are some that do lto or are fully configurable but the cheapest I've seen those for is $80.

If you don't go the series and then parallel route and opt for the more conventional parallel then series the orientation of the 12 packs is a challenge. Splitting isn't really viable so the easiest to do is just to wire the 12 cells to a fuse block (the most common of these is for boats) which both gives you cell level fuses and parallels your pack.
 

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Discussion Starter #11
I don't think those were LTO bms's, if they were send me a link. Most solar bms's balance on the high end when it hits a certain voltage. With li-ion and lifepo4 dominating the market almost all bms's start to balance in the high 3 or low 4 volt range. LTO is charged at 2.7 volts and this never hits the threshold so those bms's would never balance. There are some that do lto or are fully configurable but the cheapest I've seen those for is $80.

If you don't go the series and then parallel route and opt for the more conventional parallel then series the orientation of the 12 packs is a challenge. Splitting isn't really viable so the easiest to do is just to wire the 12 cells to a fuse block (the most common of these is for boats) which both gives you cell level fuses and parallels your pack.
Here's the link to the video where he talks about the LTO BMSs...
 

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Here's the link to the video where he talks about the LTO BMSs...
Oh ok I've seen Daly start to make LTO BMS's. For whatever reason they've all been 80A which isn't good enough for my setup which peak draw is just over 100A. You never mentioned the specifics of what voltage you're going to run at and what your peak continuous load is. You've mentioned how many packs so I gather you're building around a 40kwh pack (must be a large house you're looking to power) but not the other parameters. Is 80A going to be good enough? If so yeah you can probably get them down to $45-$50 instead of $80.

One thing I'd take a look at is Jehu has a video that shows what happens when BMS's in series trip what happens. It certainly can be done but default behavior is not what you'd expect (nor did he expect in the video). The many BMS route raises your cost but makes using the packs straightforward (and you might be wasting some cells if you are going 11s or 22s). The fuse block route makes using the packs involve a little bit of wiring up front but you don't waste any cells and it costs less than the BMS.
 

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Discussion Starter #13
Oh ok I've seen Daly start to make LTO BMS's. For whatever reason they've all been 80A which isn't good enough for my setup which peak draw is just over 100A. You never mentioned the specifics of what voltage you're going to run at and what your peak continuous load is. You've mentioned how many packs so I gather you're building around a 40kwh pack (must be a large house you're looking to power) but not the other parameters. Is 80A going to be good enough? If so yeah you can probably get them down to $45-$50 instead of $80.

One thing I'd take a look at is Jehu has a video that shows what happens when BMS's in series trip what happens. It certainly can be done but default behavior is not what you'd expect (nor did he expect in the video). The many BMS route raises your cost but makes using the packs straightforward (and you might be wasting some cells if you are going 11s or 22s). The fuse block route makes using the packs involve a little bit of wiring up front but you don't waste any cells and it costs less than the BMS.
So I'm looking to use every cell in a 24s configuration (so about 60v) and using two 48v MagnaSine 4kW inverters which have a 36 - 67.6 VDC range, so they should work nicely with 24s. Basically, I'm looking to take half my farm off-grid. I have a jet pump that runs pretty constantly during the part of the year that the sun is shining in Oregon and have a workshop that would also be powered by solar. Basically my house would remain on grid because of electric instant hot water heater and a mini-split that has turned a room into cold storage using a coolbot. These are some hogs and the hot water heater is like 28kWh so essentially impossible to run off solar at my scale.

This may be a stupid question, but the amp rating on the BMS, does going the multiple BMS route mean that I can lessen the amp to 60/50 which David Poz ordered, or does each need to match peak energy usage? I'll have to look into the fuse block route further. Thanks for the advice.
 

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So I'm looking to use every cell in a 24s configuration (so about 60v) and using two 48v MagnaSine 4kW inverters which have a 36 - 67.6 VDC range, so they should work nicely with 24s. Basically, I'm looking to take half my farm off-grid. I have a jet pump that runs pretty constantly during the part of the year that the sun is shining in Oregon and have a workshop that would also be powered by solar. Basically my house would remain on grid because of electric instant hot water heater and a mini-split that has turned a room into cold storage using a coolbot. These are some hogs and the hot water heater is like 28kWh so essentially impossible to run off solar at my scale.

This may be a stupid question, but the amp rating on the BMS, does going the multiple BMS route mean that I can lessen the amp to 60/50 which David Poz ordered, or does each need to match peak energy usage? I'll have to look into the fuse block route further. Thanks for the advice.
Parallel connections if perfectly balanced resistance wise for each path would lower the amp load on each leg evenly if wired correctly. Things are obviously never perfect but you can give some leeway and then verify with a clamp meter how many amps are running through each leg on peak load. DavidPoz has a separate video with the volt packs when he was doing this verifying each cable length was the same.

Given just how many batteries you are doing (seems like 18 packs per 4kw inverter) then your amps would be lower under normal operation and you should be fine with an 80amp BMS if I understand your setup correctly. From what I understand you are going to use each 24 pack fully in series for a 48v 24s 20ah battery with it's own daly lto BMS. These BMS's will be in parallel and hooked up to your magasine 48V 4kw inverter. If that's your setup and you have 18 in parallel your amps would be quite low. The tricky part here isn't normal operation it's having that many BMS in parallel and adding/removing packs (or the BMS or a fuse doing it for you). Adding a pack (or re-adding a pack if the bms or fuse blew) you'd definitely need the pack balanced with the other 17 before doing so or 17 parallel packs feeding the 1 will be a hell of a lot of current and will reblow your fuse/breaker. A breaker/fuse for each one is a must and personally I'm not sure I'd want that many BMS in parallel. It certainly is the least amount of work for the fit packs if you use the magnasine inverter or another inverter that accepts a high voltage range like the mpp solar pip3048lv-mk . For those you would still need to take the pack apart to remove the honda bms and add your balance leads under the screws of the honda pack but that's all you would do and could strap the bms to each pack.
 

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Discussion Starter #15
Parallel connections if perfectly balanced resistance wise for each path would lower the amp load on each leg evenly if wired correctly. Things are obviously never perfect but you can give some leeway and then verify with a clamp meter how many amps are running through each leg on peak load. DavidPoz has a separate video with the volt packs when he was doing this verifying each cable length was the same.

Given just how many batteries you are doing (seems like 18 packs per 4kw inverter) then your amps would be lower under normal operation and you should be fine with an 80amp BMS if I understand your setup correctly. From what I understand you are going to use each 24 pack fully in series for a 48v 24s 20ah battery with it's own daly lto BMS. These BMS's will be in parallel and hooked up to your magasine 48V 4kw inverter. If that's your setup and you have 18 in parallel your amps would be quite low. The tricky part here isn't normal operation it's having that many BMS in parallel and adding/removing packs (or the BMS or a fuse doing it for you). Adding a pack (or re-adding a pack if the bms or fuse blew) you'd definitely need the pack balanced with the other 17 before doing so or 17 parallel packs feeding the 1 will be a hell of a lot of current and will reblow your fuse/breaker. A breaker/fuse for each one is a must and personally I'm not sure I'd want that many BMS in parallel. It certainly is the least amount of work for the fit packs if you use the magnasine inverter or another inverter that accepts a high voltage range like the mpp solar pip3048lv-mk . For those you would still need to take the pack apart to remove the honda bms and add your balance leads under the screws of the honda pack but that's all you would do and could strap the bms to each pack.
Right on. Well its good to have a couple options at least, even if they aren't perfect. I think I'm going to pull the trigger on the batteries and I'll keep folks here apprised of my progress. I feel like, aside from the difficulties with the BMS, these batteries wouldn't be available had Will Prowse not had a negative opinion on them, so I'm thankful that the option is available, but now I'm looking at a the process of learning something new again.
 

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Right on. Well its good to have a couple options at least, even if they aren't perfect. I think I'm going to pull the trigger on the batteries and I'll keep folks here apprised of my progress. I feel like, aside from the difficulties with the BMS, these batteries wouldn't be available had Will Prowse not had a negative opinion on them, so I'm thankful that the option is available, but now I'm looking at a the process of learning something new again.
GreenTecAuto has had these for sale since 2018 long before Will's video. His opinion on LTO is likely due to getting grade B Yinlong cells when he was expecting new 40ah Yinlong cells. Why he's never gone back and corrected that I don't know. That being said new LTO cells are much more expensive than Li-ion or LifePO4 cheapest is around $0.65/Wh compared to $0.37/Wh for LifePo4 or $0.20/Wh for Li-ion.

Obviously if you need what LTO excels at it's a no brainer (long life, low temperature, high charge/discharge rates) but if you don't need either of those 3 paying 3x or 4x doesn't make sense. The price differential in the used market is even larger but it's where LTO's long cycle life comes in handy as well. That being said in general using LTO makes sense if you need what it's good at otherwise there are cheaper options, for my use case it happens to be low temperature that I need. Will being located in Las Vegas obviously doesn't have that need and solar certainly doesn't need high charge/discharge rates.
 

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But solar (which can opperate for decades) is an excellent fit for the long cycle life.
For sure but we're comparing them against each other not against lead acid. Manufactures vary but as an approximation let's call li ion 1800 cycles, lifepo4 7000 cycles, and lto 20000 cycles and each has it's step down in nominal voltage (3.7, 3.2, and 2.3v). Most solar is going to cycle daily max so we're talking 5 years vs 20 vs 50. I can see that argument for the 5 year timeframe but not 20 years vs 50 because there v is also calendar aging that takes place not just all cycles.
 

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For sure but we're comparing them against each other not against lead acid. Manufactures vary but as an approximation let's call li ion 1800 cycles, lifepo4 7000 cycles, and lto 20000 cycles and each has it's step down in nominal voltage (3.7, 3.2, and 2.3v). Most solar is going to cycle daily max so we're talking 5 years vs 20 vs 50. I can see that argument for the 5 year timeframe but not 20 years vs 50 because there v is also calendar aging that takes place not just all cycles.
yup ..
Seems to me your own numbers just made a good case for the LTO's longjevity being better for solar.
;)

While the ~20,000 cycles ~54 years .. without that additional calendar aging effect that's still nearly ~1/3 of the capacity loss per year due to cycling (compared to LiFePO4) .. sure the calendar effect also degrades it .. but it still will last much longer than even the LiFePO4 (under similarly hard conditions).

Your 7,000 LiFePO4 cycles is ~19 years if only cycled .. without that additional calendar aging effect you sited .. which at 1 such cycle per day .. is roughly ~1 % loss per year from cycling alone.

attached bellow is the aging graph for the 20Ah pouch A123 style LiFePO4 cells .. the effect is mostly temperature related .. loosing 2-8% per year .. at the low end .. only ~2% per per year to aging and no cycling will put it around ~82% left after ~10 years of storage.

combine the ~2% per year aging .. plus the ~1% per year cycle .. and you're up around ~3% per year of losses in capacity .. at that about ~3% your below the 80% of original capacity in about ~7 years.

even if you only had ~2% from both (cycle and age) you are still down to ~82% left after just ~10 years .. will cross the under the ~80% left point in less 20 years .. unless you never use them .. store them at low SoC in a refrigerator.

Keeping in mind that a good quality solar panel system itself can still have up around ~80% of it's original capacity after 20 years .. the LifEPO4 is good .. but it degrades faster than the solar panels themselves , and faster than the LTO will .. now .. if / when LiFePO4 is say in the range of 1/2 to 1/3 the price of LTO .. sure it can still be cheaper in the long run .. but when we are getting these SCiB LTO for around ~$240 per kwh ($265/1.1kwh) .. the 1/2 point for LiFePO4 would be about ~$120 per kwh .. the 1/3 point for LiFePO4 would be about ~$80/kwh .. and LiFePO4 is just not usually that much cheaper .. cheaper yes .. but not that much cheaper.
 

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yup ..
Seems to me your own numbers just made a good case for the LTO's longjevity being better for solar.
;)

While the ~20,000 cycles ~54 years .. without that additional calendar aging effect that's still nearly ~1/3 of the capacity loss per year due to cycling (compared to LiFePO4) .. sure the calendar effect also degrades it .. but it still will last much longer than even the LiFePO4 (under similarly hard conditions).

Your 7,000 LiFePO4 cycles is ~19 years if only cycled .. without that additional calendar aging effect you sited .. which at 1 such cycle per day .. is roughly ~1 % loss per year from cycling alone.

attached bellow is the aging graph for the 20Ah pouch A123 style LiFePO4 cells .. the effect is mostly temperature related .. loosing 2-8% per year .. at the low end .. only ~2% per per year to aging and no cycling will put it around ~82% left after ~10 years of storage.

combine the ~2% per year aging .. plus the ~1% per year cycle .. and you're up around ~3% per year of losses in capacity .. at that about ~3% your below the 80% of original capacity in about ~7 years.

even if you only had ~2% from both (cycle and age) you are still down to ~82% left after just ~10 years .. will cross the under the ~80% left point in less 20 years .. unless you never use them .. store them at low SoC in a refrigerator.

Keeping in mind that a good quality solar panel system itself can still have up around ~80% of it's original capacity after 20 years .. the LifEPO4 is good .. but it degrades faster than the solar panels themselves , and faster than the LTO will .. now .. if / when LiFePO4 is say in the range of 1/2 to 1/3 the price of LTO .. sure it can still be cheaper in the long run .. but when we are getting these SCiB LTO for around ~$240 per kwh ($265/1.1kwh) .. the 1/2 point for LiFePO4 would be about ~$120 per kwh .. the 1/3 point for LiFePO4 would be about ~$80/kwh .. and LiFePO4 is just not usually that much cheaper .. cheaper yes .. but not that much cheaper.
Typically LifePO4 is about half the cost of LTO. Obviously better deals can be found around the holidays for LifePO4 but currently it's about $137/kWh for used cells. Not exactly half but pretty close. LTO definitely lasts longer than LifePO4 which already lasts long, my main thing when we're talking that long is the number of applications goes down due to costs going down and further breakthroughs happening. If the application doesn't matter and is in the middle of nowhere and you just want set it up and forget about it for a half century sure but if this is going on your house and you replace them at 20 years this isn't necessarily because the product isn't working as designed even if it's LTO. Larger batteries in the future could cost a lot less, a new tech breakthrough in batteries/panels or both could outperform today's tech of any kind by a lot, or other unforeseen stuff. The longer the timeframe the more likely vastly better stuff will be cheaper than today's stuff (not a guarantee but tends to happen especially in tech). Saving half of your money today and spending it at 20 years instead of 50 isn't necessarily a loss depends on what you can get in 20 years for those dollars.
 
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