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Energy storage 18650 up to 24kWh class Paragon, Powerwall

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  • #31 21277727
    remzibi
    Level 24  
    LEDówki wrote:
    ...... is there a protection device, the so-called BMS? What maximum current does it have? What are the limiting voltages? Does it have a circuit that balances the voltage of the cells in the battery?.......


    Yes it does, JKBMS and has the following settings
    BMS up to 150A, but is set to charge 50A, discharge 50A, once storage is topped up it will be increased accordingly.
    Limit voltages as for Li-Ion cells 2.9V to 4.2V

    On the other hand, operation with storage is set on the inverter, landing current 40A, limit voltages per cell 3.3V to 4.13V , iron reserve in case of grid failure is milked to 3.1V after which the inverter shuts down.


    LEDówki wrote:
    ..... It is very likely that the Author has not read anything on how electrochemical cells are connected........


    Oh not really, not really :)

    I will also clarify that I sourced random cells, whereas after testing and selection they are no longer random, the strings were carefully selected in terms of cell capacity and internal resistance, and even origin and company. But thanks for your concern :) .


    To avoid ambiguity I add here and the first post
    Diagram of the warehouse, connection to the BMS
    Wiring diagram for 14S BMS and energy storage connection.
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  • #32 21277780
    LEDówki
    Level 43  
    Limiting the maximum and minimum voltage has the effect of extending the life of the batteries. In this case, the protection can be set, as in the case of a colleague, to extreme values, i.e. 2.9 V (this could be increased to 3 V) and 4.2 V (the catalogue maximum battery voltage is 4.15 V +- 0.05 V i.e. 4.1 V - 4.2 V).
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  • #33 21277865
    E8600
    Level 41  
    I recall correctly that the author has a YT channel and there was a small incident of testing/selecting links?
    remzibi wrote:
    40 strings x 6 cells (target)
    .
    3360 links only. As long as the structure is enclosed in some garage away from the house then the idea is very good only the security is worth refining. I would absolutely not keep that many cells in the house even if they were new.

    Such solutions are until I saw a similar DIY warehouse, because the author lives in the islands, he did not enjoy it even a year came the sad gentleman from the energy and the warehouse had to disappear because it does not have the required safety certificates and in case of "W" there will be no compensation from insurance and even will be a potential culprit if, by the way of fire, the houses of neighbours suffered. In Poland, such inspections will also come into force in time, and insurance companies will find qualified experts and in the event of a DIY project without certificates, there will be a problem.

    BTW
    This is not why there were subsidies for "ecology" so that people could have something for free. I would believe in free electricity in Africa or Cambodia, but not in European countries.
  • #34 21277893
    Marcin125
    Level 29  
    I read 'ecology' somewhere in here and stopped reading further.... :) .
    Perhaps it should be "education" instead.
  • #35 21277899
    andrzejlisek
    Level 31  
    As far as the fire risk of the warehouse in question is concerned, is it possible and sensible to implement one of two ways:

    1. enclosing the entire warehouse in an airtight metal or glass can (no matter what, the important thing is that it is made of a rigid, non-flammable and gas-tight material) and connecting a vacuum pump. The pump will draw out the air to create a reasonably low vacuum. Such a vacuum is far from the vacuum required in electron tubes, but the idea is to reduce the amount of air considerably. As far as I know, without air, combustion is not possible. Alternatively, instead of making a vacuum, you can let in any gas that is readily available, cheap, non-flammable and other than oxygen. As far as I know, combustion is not possible in a vacuum or in, for example, nitrogen alone. This idea comes from this experience: https://www.youtube.com/watch?v=KiwVOz8cHpI If you deprive the air of oxygen, replace it with a vacuum or another gas, nothing can burn.

    2. immerse the whole store in transformer oil. Such oil is non-flammable, but electrical wiring can "dive" into it (which cannot be said for water). In theory, transformer oil will not only completely prevent the cells from igniting, it will also facilitate heat dissipation.

    It is known that this is some investment, but the question remains, does it actually improve fire safety?
  • #36 21277999
    shimano73
    Level 12  
    Could someone please draw me a block diagram of how this is all connected together , is a hybrid inverter used here ? . I have a 9kW installation with a Fronius Symo 8.2 inverter, is there any way of switching this on?
  • #37 21278013
    Olkus
    Level 32  
    I am impressed with the design - congratulations.
    On the other hand, in terms of safety, haven't you thought about fitting some temperature sensors/fuses that will disconnect the system if the package temperature rises too high?

    Regards,
    A.
  • #38 21278020
    remzibi
    Level 24  
    shimano73 wrote:
    ..... is a hybrid inverter used here ? . I have a 9kW system with a Fronius Symo 8.2 inverter can this be switched on somehow ?


    Yes, I have a 5.5kW hybrid inverter.
    I'm not familiar with this Fronius, so unfortunately I won't answer whether connecting any storage is possible, let alone how to do it


    Olkus wrote:
    I am impressed with the design - congratulations.
    On the other hand, in terms of safety, haven't you thought about fitting some temperature sensors/fuses that will disconnect the system if the package temperature rises too high? ........
    A.
    .

    Thanks for the good word :) .
    Yes the Temperature sensors are from the BMS and are distributed along the warehouse.
    After that cyclic thermal imaging control, mainly during high sunlight at high charging currents, i.e. maximum set charging current of 40A.
  • #39 21278080
    Janusz_kk
    Level 39  
    andrzejlisek wrote:
    As far as I know, no combustion is possible without air.
    .
    But li-ons and the like do not need air to burn, and this is the main and fundamental problem in extinguishing them, no foams or Co2 give anything, the only thing left is immersion in water and cooling to stop the reaction and waiting.

    andrzejlisek wrote:
    Submerge the whole stock in transformer oil.


    Oil is oil, burning lithium will easily ignite it, that's why nobody (electric cars) cools cells with oil only with water and alcohol solutions to make it frost proof.
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  • #40 21278204
    andrzejlisek
    Level 31  
    I always learn something new, and it's very good. Until now, I was convinced that the biggest problem with lithium and li-ion cells is that the mere contact of lithium with air causes spontaneous ignition, which happens if there is even a little damage to the cell casing. https://www.youtube.com/watch?v=CGQwqWqzkNA In general, it is this fact that starts the subject of magazine fires made of hundreds of 18650 cells. All it takes is for one to catch fire, the fire damages the next and spreads to the whole magazine just like domino blocks falling over.

    As far as I remember, any combustion requires oxygen. I don't know where a burning lithium would get its oxygen from if not from the environment, but I accept that it is impossible to extinguish it by any other means than immersion in water. My idea came from the fact that, in theory, combustion should not be possible if the combustible material is immersed in a non-combustible liquid or surrounded by a non-combustible gas other than oxygen. Since oil is flammable, water is rather incompatible with electricity for other reasons (unless distilled water, but I'm not sure about that, whether a cell battery can be immersed in such water), I don't know what liquid or gas would meet the assumption. Although it is already clear that carbon dioxide does not meet it, since it will not extinguish a burning battery.

    Added at 6 [minutes]:

    remzibi wrote:
    I will also clarify that I sourced random cells, whereas after testing and selection they are no longer random, the strings were carefully selected in terms of cell capacity and internal resistance, and even origin and company. But thanks for your concern
    .

    I will ask, if you don't mind, what percentage or so of the cells received pass the tests and are suitable for stock use? I understand that the source of the cells are laptop batteries destined for disposal due to damage preventing use in a laptop.

    The solution used in this particular warehouse has a very important advantage. The investment in the cells themselves can be spread over instalments, only the rack and electrical connections had to be done 'at once'. As more cells arrive, one will slowly add to the storage until it is full. And then, just as slowly, you can replace the most passed cells with copies that are in better condition. I assume that the 'influx' of further 18650 cells, with some percentage being suitable for further use, will not end when the rack is full.
  • #41 21278230
    Janusz_kk
    Level 39  
    andrzejlisek wrote:
    I don't know where burning lithium would take oxygen from if not from the environment,
    .
    Yes, from the environment, but it's not the air it's the electrolyte, it breaks down the water and 'extracts' the oxygen from the hydrogen.
    andrzejlisek wrote:
    Since the oil is flammable,
    .
    You know at its operating temp which is say max 200st it is probably not flammable, but from a certain temp everything is flammable :( and lithium burns at high temp.
    andrzejlisek wrote:
    unless distilled water, but I'm not sure a cell battery can be immersed in such water)
    .
    In such you can. It is the dissolved salts that give the water its conductivity.
  • #42 21278484
    remzibi
    Level 24  
    andrzejlisek wrote:
    ......
    I would ask, if I may, what percentage or so of the cells received pass the tests and are suitable for use in storage? I understand that the source of the cells are laptop batteries destined for disposal due to damage preventing use in a laptop.

    Laptop batteries are by and large the worst cells and there are few of them in stock, I estimate around 15% maybe 20%. On the other hand, these 80-85% of the stock are cells from large packs such as bicycles or other "vehicles", this is the best option because we have a large number of more or less identical cells with identical parameters and after tests it is easy to assemble strings from this.
    The percentage of recovery varies greatly; after tests, there is a lot of 'waste' from laptop cells, probably 50% if not more.
    Cells from large 'vehicle' packs are much better, but also the percentage of 'waste' is probably around 30% (I have never counted this).
    But there are various situations, I remember 4 large 'vehicle' packs with over 50 cells each, after tests there were 3(in words, three) cells left :) - a total failure.
    But for example from other packs, where somewhere moisture got into them and e.g. the BMS went crazy or e.g. 3 cells corroded, the BMS got blocked and the pack went to scrap, after unpacking and knocking out those 3 cells, all the rest are super cells keeping factory parameters and not just any cells - such cases are a success.
    As far as the "waste" is concerned, I also divide it into total waste for disposal, and such cells which did not qualify for the warehouse, because, for example, one cell has a lower capacity than the rest of the batch, i.e. it is already "tired"; it does not go to the warehouse, but to home torches, power-banks or other workshop devices, e.g. a component tester, oscilloscope, meter, etc. or other applications. Generally I try not to let anything go to waste, I use one larger power bank in such a way that I connect such a USB heated double shoe to it and warm my feet in the evenings :) .


    andrzejlisek wrote:
    ......
    The solution used in this particular warehouse has a very important advantage. The investment in the cells themselves can be spread over instalments, only the racking and electrical connections had to be done 'at once'. As more cells arrive, one will slowly add to the storage until it is full. And then, just as slowly, you can replace the most passed cells with copies that are in better condition. I assume that the "influx" of more 18650 cells, with some percentage of them suitable for further use, will not end when the rack is full.

    Exactly right. This is why I chose the 'Paragon style' design :) .
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  • #43 21278516
    jonex21
    Level 12  
    View of an open laptop with visible battery cells labeled as A, B, C, D, E, and F with given capacities. .

    A little off topic in relation to link linking.

    Question-interest how are the battery cells connected in the photo? For ease of reference, the cell capacity is given .
  • #44 21278572
    tatanka
    Level 21  
    How much time did you spend on the construction ?
    How much did the material cost ?
  • #45 21278624
    kkknc
    Level 43  
    You could get quite a lot out of old laptop cells, of course the Dell branded cells because the bms usually died in them. So I was recovering quite a lot. Some time ago I received probably 150 batteries, after reviewing all of them I can see that they are simply worn out, their nominal capacity has dropped to 1/3 or 1/4 of the nominal capacity so they are no longer usable. There were a few that had 50% more capacity.
  • #46 21278634
    remzibi
    Level 24  
    tatanka wrote:
    How much time did you spend on the construction ?
    How much did the material cost ?
    .

    The construction of the frame/frame alone, without the links, was about 3 weeks, yes an hour two in the afternoons.
    The material and accessories absolutely necessary for the construction and operation but without the cells, i.e. all the accessories with BMS, chargers, dischargers, thermal imaging camera, shirts, spacers, welding tape, welder, screws, wires, cable crimps with crimping tool (the one I had left in total after setting up the solar panels), etc. is about maybe 2200pln

    The time to test the cells and the cost of sourcing them is another story, it will probably look different for everyone.

    Added after 1 [hour] 9 [minutes]: .

    jonex21 wrote:
    ......
    Question-interest how are the battery cells connected in the photo? For ease of reference it is given cell capacity .
    .
    What, you don't have a meter and a question for the clairvoyants? :) .
    Measure and write us, we'll know too. To make it easier we are not going anywhere :) .
  • #47 21279041
    jonex21
    Level 12  
    remzibi wrote:
    ... And what, you don't have a meter and a question for the clairvoyants? :) ...
    .

    Sorry, but my question was misunderstood ;) I know exactly the answer :) .
    From the discussion in other posts there was some confusion :( By asking such a question I wanted to show that you don't always have to use the same ( capacity ) cells to make a battery. The only thing to remember is that the capacity of the cell in parallel connection should be the same as the other cells connected in series and the type of cell should be the same.

    Interior of an open laptop with labeled battery configuration and capacities. .

    LEDówki wrote:
    ... 100 la ago there were electric cars with lithium-ion battery packs ...


    What can you learn from the internet 100 years wow ;)
  • #48 21279069
    LEDówki
    Level 43  
    Do you think that here Link they have written untruths?
  • #49 21279075
    Oddawajsanki
    Level 7  
    Congrats on the workmanship, and have you thought about safety?
  • #50 21279131
    remzibi
    Level 24  
    jonex21 wrote:
    .... The only thing to remember is that the capacity of the cell in parallel connection should be the same as the other cells connected in series and the cell type should be the same......


    Well, and a good example, the "Apple style" cells :) .



    Oddawajsanki wrote:
    Grats on the workmanship, and have you been mulling over safety?


    Thanks for the good word :) .
    Not even that I've been cumming (whatever that means), but I've been cumming (whatever that means) all along over security :)

    Added after 7 [minutes]:

    LEDówki wrote:
    You think that here Link they have written untruths?


    BTW the credibility of this "portal" is highly debatable (I know from personal experience what idiocies they write) - a kind of sponsored left-wing brainwashing portal for the economics, stock market and history handicapped :) .
    Error message from Business Insider indicating a missing page.
  • #52 21279376
    Stanley_P
    Level 28  
    jonex21 wrote:
    LEDówki wrote:
    .... 100 la ago there were electric cars with lithium-ion battery banks ...


    What can you learn from the internet 100 years wow

    Hm, I didn't find a single word in this otherwise probably sponsored leftist brainwashing article that 100 years ago lithium-ion(?) batteries were used in the electric cars of the time. On the contrary, only lead-acid ones. With regard to Li-ion it only says, quote:
    Quote:
    The lead-acid battery, which was invented back in 1859 by the French physicist Gaston Planté even after improvements, was at the turn of the 20th century far less efficient than the lithium-ion batteries used in today's electric cars.

    And
    Quote:
    even today's lead-acid batteries store several times less energy than lithium-ion batteries of similar weight. This means that without modern battery technology, electrics would have several times less range.
    .
    On the other hand, I found an article that yes, counting 100 years - the inventor of the Li-ion battery died last year:
    https://evertiq.pl/news/31076
    and the first concrete work to develop them, so to speak, did not take place until the late 1970s/early 1980s.
    A few words about the history of Li-ion are e.g. here:
    https://blog.swiatbaterii.pl/bateria-litowo-jonowa/

    As for the error in the link originally provided by @LED's - the letter "l" was missing at the end (like a lefty ;-) ) However, you could easily find by the title of the article, overtly located just in the link.
  • #53 21279716
    speedy9
    Helpful for users  
    I like your design. I also agree with your opinion on lithium polymer batteries, I have had similar experiences. I myself own 18650 Li-Ion batteries that are about 25 years old. They are still working. The 18650s, are quite 'armoured', and it is not so easy to damage them mechanically, unlike the softer Li-Po ones, which I will say frankly I sometimes dread removing from devices to replace. Often they are glued with strong tape and bend when trying to peel them off, damaging the internal structure and possibly the 'packaging' itself.
    remzibi wrote:
    current capacity unproblematic, where per cell the currents are in the order of 250-350mA, which will hopefully provide many years of service life.
    .
    I may have missed this somewhere in the description, but why did you decide to go for this, all in all, rather low usable discharge current? Boosting the current to 500mA, which is typical for standard cells, is unlikely to shorten their life noticeably, and you will need fewer cells. For what it's worth, setting the discharge to 3.3 and the charge to 4.13V is a very good step. This undoubtedly has a positive effect on the life, as Li-Ion in particular "dislikes" discharging below 20% and charging to 100%.
  • #54 21280003
    airman
    Level 13  
    Hi, Have you not thought to make a 15S ? I assume you have one of the Chinese hybrids that can charge up to 60v max which gives you charging the cell up to 4v you will reduce the capacity slightly but combined with the low current draw the life increases.
  • #55 21280018
    nemmm
    Level 13  
    Janusz_kk wrote:
    andrzejlisek wrote:
    I don't know where burning lithium would get oxygen from if not from the environment,
    .
    Yes, from the environment, but it's not the air it's the electrolyte, it breaks down the water and 'pulls' the oxygen out of the hydrogen.


    I don't know anything about electronics but it's been a long time since I've read such a load of crap. I really recommend taking a look at a chemistry book, even one for 8th grade is enough to see what happens when lithium combines with water and what burns. For those interested, here is a video

    https://youtu.be/Vxqe_ZOwsHs

    As you can see in the video metallic lithium is usually stored in paraffin, it is a soft metal and can be cut with a knife. The cut lithium (nice metallic surface) does not ignite in air but passivates by reacting with CO2 from the air and lithium carbonate is deposited on the surface. Later in the video you can see that the lithium reacts violently with water but still does not ignite. Lithium reacts with water to produce lithium hydroxide (non-flammable) and hydrogen, and this is the cause of the fires. In a closed vessel, when it is short-circuited, a sufficiently high temperature occurs to start an ignition.

    And here are tests of individual batteries and the time it takes for them to explode and/or ignite.
    https://youtu.be/Qzt9RZ0FQyM

    As you can see in the video, when the cells are overcharged the electrolyte starts to decompose which causes us to produce flammable gases and the cells swell until the casing ruptures and the hydrogen ignites due to an accidental spark. You can see how the corresponding LI-ION, LiFePo4 and LTO cells behave

    And here is an even better video comparing lithium, sodium and potassium. Na-ION sodium batteries, will be even more flammable:) .

    https://youtu.be/jI__JY7pqOM

    Luckily potassium will not be used in batteries for various reasons.
  • #56 21280092
    Janusz_kk
    Level 39  
    nemmm wrote:
    I really recommend looking at a chemistry book, even one for 8th grade is enough to see what happens when lithium combines with water and what burns.
    .
    What does it matter? It breaks down water or not, it burns? burns so apologise.
  • #57 21280095
    nemmm
    Level 13  
    Janusz_kk wrote:
    nemmm wrote:
    I really recommend looking at a chemistry book, even one up to 8th grade is enough to see what happens when lithium combines with water and what burns.
    .
    What does it matter? It breaks down water or not, it burns? it burns so apologise.


    Lithium doesn't burn:D Hydrogen burns:)
  • #58 21280107
    Janusz_kk
    Level 39  
    Doesn't matter, what matters is the end result, in the context of answering the question I was right that it breaks down the electrolyte
    nemmm wrote:
    Janusz_kk wrote:
    Janusz_kk wrote:
    andrzejlisek wrote:
    I don't know where burning lithium would get oxygen from if not from the environment,
    .
    Yes, from the environment, but it's not the air it's the electrolyte, it breaks down the water and 'extracts' oxygen from the hydrogen.


    so you are still a beetroot to me for those words because it decomposes water i.e. figuratively 'pulls out' oxygen, i.e. i was right.
    nemmm wrote:
    I don't know anything about electronics but I haven't read such a piece of crap for a long time.

    and on air the lithium would not ignite by itself due to insufficient water.
  • #59 21280112
    nemmm
    Level 13  
    Janusz_kk wrote:
    It doesn't matter, it's the end result that counts, in the context of answering the question
    nemmm wrote:
    Janusz_kk wrote:
    Janusz_kk wrote:
    andrzejlisek wrote:
    I don't know where burning lithium would get oxygen from if not from the environment,
    .
    Yes, from the environment, but it's not the air it's the electrolyte, it breaks down the water and 'extracts' the oxygen from the hydrogen.
    .

    so you are still a beetroot to me for those words
    nemmm wrote:
    I don't know about electronics but I haven't read such bullshit for a long time.


    I see that you, instead, are a specialist (chemist) without elementary knowledge of chemistry.

    Like that Janusz from the internet,

    kind regards

    Added after 1 [minute]:

    >>21280107 .

    poured over water, thrown into water, etc. also does not ignite. Never mind that you can see with your own eyes that it doesn't catch fire, you said once that it does catch fire and you will stick to that. The main thing is to stick to your opinion!

    As I have already started this topic of the chemistry of cells (batteries?) containing lithium this is one of the reasons why these batteries are discharged before destruction. In a discharged battery we have 99% Li+ ions which are completely stable and non-flammable. I am interested in cell chemistry by virtue of my profession and look forward to reading this:

    https://nanografi.com/blog/ironair-batteries-...2BspheXDVvNL_Px6GBASo713AQjhpaYwFcEiLrklKM27w

    A huge amount of the problems of large energy storage will be solved and the price of the cell should drop 4-5 times per kWh.
  • #60 21280152
    pawciu-85
    Level 36  
    I personally saw on the S7 at Wolica how a carton of smartphone cells on the back of a bus caught fire of its own accord. The cells were disassembled from the smartphones and packed into the cardboard box. Even covering them with firefighting foam, which cuts off the oxygen supply from the air, did not help. There were some bubbles coming out from under the foam and the cells did not lose temperature. It was only when they were thrown into a barrel of water that the reactions in them were definitively terminated.
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Topic summary

The discussion centers on a DIY 48V energy storage system built using recycled 18650 lithium-ion cells, achieving an estimated capacity of around 12kWh currently, with plans to exceed 24kWh. The system is inspired by the "Paragon" class energy storage concept and is designed to power a home for up to two cloudy days or about 36 hours under heavy use. Key technical aspects include the use of a JKBMS battery management system with settings for 50A charge/discharge limits, voltage thresholds between 2.9V and 4.2V per cell, and thermal monitoring primarily via thermal imaging to detect early cell anomalies. The cells are carefully tested and matched by capacity and internal resistance, with a preference for cells from large vehicle packs over laptop cells due to better uniformity and reliability. Safety concerns are addressed through distributed temperature sensors, BMS protections, and housing the storage in a dedicated, fire-separated room. The discussion highlights the fire risks associated with lithium-ion cells, especially compared to lithium polymer cells, which degrade faster and are more prone to ignition. Various opinions emphasize the importance of proper cell balancing, BMS functionality, and the challenges of using mixed or random cells. The system uses a 5.5kW hybrid inverter, with charging managed in constant current/constant voltage (CC/CV) mode by the inverter and balancing handled by the BMS. Thermal imaging is preferred over continuous sensor monitoring for early detection of cell issues. The storage is kept in a heated, insulated room to avoid cold-related degradation. The conversation also touches on broader energy market dynamics, such as negative electricity pricing and the impact of renewable energy sources on grid stability. Alternative battery chemistries like LiFePO4 (LFP) are mentioned as safer and more fire-resistant options, though the DIY project focuses on repurposed 18650 Li-ion cells. The overall consensus is that while DIY 18650 storage is feasible and cost-effective, it requires meticulous cell selection, robust monitoring, and safety measures to mitigate fire risks and ensure longevity.
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