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Energy storage 18650 up to 24kWh class Paragon, Powerwall

remzibi 15141 144
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  • #121 21295459
    pawciu-85
    Level 36  
    metalMANiu wrote:
    The problem is that no one but the residents benefit.


    The problem will be that it would take years to complete the formalities at the Polish Water Authority, then the project, water rights and environmental decision, land ownership, and finally the building permit. Taxes as for a hydroelectric power plant and all in all, with small capacities, it will be cheaper to buy such a volume from the DSO.
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  • #122 21295827
    partyzancik
    Level 24  
    gulson wrote:
    That is why it will be hard, because the whole of Europe is lagging behind, but I am optimistic 💪
    .
    Not all of it, just the countries that joined the eu in 2004 and after. The old 15 are fine unless you are talking about southern countries such as Greece, Spain and Portugal which have not progressed too much.

    Added after 48 [minutes]:

    @remzibi and if the cells heat up when charging you immediately dismiss it? I even when charging with tp4056 the sanyo heats up and all batteries with them I threw in the scrap.
  • #123 21296236
    Damian_Max
    Level 19  
    @andrzejlisek As if you had energy storage that would last a year (xD), it would be enough to charge it with PV alone, in the sense that with the money for windmills and waterwheels you would also buy PV.

    As for the project itself I'm impressed too, you can see a great deal of time spent, congratulations!
    It's a bit inspiring, but the resulting device also carries no small risk. It could be minimised by moving the store away from the house, building it with non-flammable materials, maybe even dividing it a little into several smaller ones, monitoring it, plus some kind of automatic incident response system (disconnection / maybe fire extinguishers).
    Probably counting some reasonable man-hours, the whole project would not make economic sense, but after all, you have to do something in your spare time, and the resulting construction is certainly pleasing to the eye.

    All in all, I still have a question, maybe to the author or maybe someone else knows the answer, about the discharge of the (used?) cells themselves. Does it differ significantly from one cell to another, can it be measured somehow, should I be worried about it?
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  • #124 21296246
    yogi009
    Level 43  
    In my opinion, assembling batteries from different cells is a bad idea. The choice of Li-Ion technology should result in the energy storage being moved to an external container (preferably an isotherm). And a third point: I would consider LiFePO4 cells as less prone to fire and higher current capacity and longer life.
  • #125 21296653
    remzibi
    Level 24  
    andrzejlisek wrote:
    @remzibi .... Suppose you just take apart another battery from an electric scooter and find most of the cells usable, do you also do a voltage equalisation before attaching to the storage?
    .

    Yes, of course , before I weld another module of cells, they all have their voltages equalised, after about a month's storage it is usually between 4.13V-4.15V.
    I plug the next string of 14 welded modules into the magazine when the magazine is fully charged and therefore also has 4.13V-4.14V per cell (which is meticulously taken care of by the balancer), then no current flows after plugging in and there is no need to fiddle with any equalising resistors. When the sun goes down in the evening, the new added cells already discharge normally with the rest of the storage and enter their normal cycle with the whole.
  • #126 21297512
    Anonymous
    Level 1  
  • #127 21297621
    p.obelix
    Refrigeration equipment specialist  
    >>21297512
    Heating a house with a heat pump means that 4000-5000 kWh are needed for the heat pump alone plus a house of 3000 kWh also you can multiply and add and it will never be enough.
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  • #128 21565641
    remzibi
    Level 24  
    Update, it's been over a month since the magazine completely paid for itself, so after a full financial 'blip', everything is now going to the upside.
    As befits an experimental magazine - the experiment continues - and the mothballing continues :)

    Next news, sometime in March I noticed that some of the cell sockets from one batch started to crack after a while, so within two weeks (fortunately these were weeks of no sunshine at all) the storage unit was rebuilt to mechanically prevent this kind of malfunction in the future. The cracked sockets were replaced. The sockets that have the print on them are OK and nothing happens to them, but the ones from the Chinese supplier that don't have such prints and numbers - they started to break, so I LOSE to the quality of some Chinese stuff.
    Below are pics of how they break down and how I rebuilt the magazine (disassembling/disassembling it was one afternoon - I was surprised myself how quickly you can take something apart :) ) . This info would actually need to be added to the first post.

    Close-up of a damaged plastic battery holder for cylindrical cells, visible crack on the left side. Close-up of a cracked battery holder slot in a plastic cell holder. .

    Wooden energy storage frame with rows of black plastic battery holders, two white containers with additional connectors on the surface. Rows of black battery cells connected with copper busbars, arranged on a wooden background. .


    By the way, I throw in an example of a cell caught during a periodic thermal imaging inspection, a point of higher temperature by 3 degrees relative to the background, a cell that got a slight leak (after removing the tee shirt, I found a tiny electrolyte leak, a droplet). There was still a long way to go before such a cell was destroyed, maybe 3-6 months, but the thermal imaging had already caught the "dude" early enough - the cell was of course replaced immediately (without shutting down the storage), service-wise the design works.
    Here the thought really comes to mind that if the factory packs were not sealed and people/users were able to check with thermal imaging, the number of different "accidents" could be significantly reduced.

    Thermal image of a battery cell with a local temperature rise up to 25.5°C against a background of about 23°C. Thermal image of a single cell showing a hot spot with a temperature of 21.8°C.

    partyzancik wrote:

    @remzibi and if the cells heat up when charging do you just blow it off? I have had sanyo cells heat up even when charging with tp4056 and I have thrown all the batteries with them in the scrap


    Yes, with a 700mA landing current, anything above 40 deg C drops out automatically, cells usually start to heat up when charged above 3.9V, charging of course I check with thermal imaging and not "finger" :) .
    Example photo of a thermo cell which will be discarded in a moment

    Thermal image showing three cells in a charger, one cell reaching 38.3°C.
  • #129 21565809
    gulson
    System Administrator  
    Thank you so much for updating the topic and sharing the link control. I can see that you are approaching this professionally, one can take example from you.
  • #130 21583514
    partyzancik
    Level 24  
    @remzibi And how about cells discharged to zero ? Do you manage to pick them up and use them normally or trash them ?
  • #131 21583771
    Strumien swiadomosci swia
    Level 43  
    Yes will raise the link but it is a lottery what happens afterwards.
  • #132 21583778
    LEDówki
    Level 43  
    >>21583514 It depends on how long they have been discharged. They certainly lose a lot of capacity and their internal resistance increases. I disposed of two of these. They seemed to charge, but not fully and they were hot. About 10% of the original capacity remained. This is why PCM protection circuits are used for these batteries, so that such situations do not occur.
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  • #133 21583803
    yogi009
    Level 43  
    There is no room for debate here. A cell discharged in this way does not return to its normal condition and must be replaced.
  • #134 21583910
    kkknc
    Level 43  
    Even if it doesn't heat up. It still has a fair amount of capacity loss.
  • #135 21584666
    remzibi
    Level 24  
    partyzancik wrote:
    @remzibi And how about cells discharged to zero ? Can you pick them up and use them normally or trash them ?
    .

    Yes, all cells discharged to 0V or almost 0V I try to "pick up" as much as possible, firstly by boosting with a current of 50-100mA to a voltage of about 2.8V 2.9V 3V, then a short rest of about 24 hours to see if there is a rapid self-discharge, and if the voltage has dropped (there is self-discharge) then the cell is immediately discarded. If the voltage holds, the cell is put through its normal cycle of testing for heating, capacity, Rwew, one month's ageing, etc.
    Approximately 65% of fully discharged cells normally pass the tests and are put into service, 35% are rejected - generally the same ratio as with cells still holding some voltage, so the fact that a cell is completely discharged is no indication of anything, and certainly not of its current condition.
    If the cell passes the tests, I do not even observe a drop in capacity, it works normally like the others and holds the parameters.
    If, however, the capacity of the cell deviates significantly from the nominal value (chemical degradation and increase in internal resistance are connected with a drop in capacity), such a cell is intended for torches, cleaning robots (converted to 18650), meters (most meters in my workshop are converted to 18650), or other undemanding power banks or powering household appliances.
  • #136 21584740
    LEDówki
    Level 43  
    Not everyone has that many batteries discharged to zero to do tests. I had 2 in a 5 pc battery and both had a high self-discharge current, they were heating up so I blew them out. They passed the capacity test at once. I didn't have room for the electro-waste. I have torches with NiMH batteries. The cleaning robot also has a NiMH battery pack, so the electro-waste went into the electro-waste.
    Your experience, on the other hand, proves that it is worth trying to salvage deeply discharged batteries if there is a use for them.
  • #137 21584832
    partyzancik
    Level 24  
    LEDówki wrote:
    The torches I have run on rechargeable NiMH batteries.
    I understand this because instead of AA and AAA cells
    LEDówki wrote:
    The cleaning robot also has a rechargeable NiMH battery,
    .

    I wonder why for an 18650 it would have more energy packed in there ? What kind of NiMH cells are in the robots ? Ordinary or high current ? I have one blue and one yellow from an Irobot and maybe I could power some power tools
  • #138 21584862
    remzibi
    Level 24  
    partyzancik wrote:
    ...... on 18650 would have packed more energy in there ? What kind of NiMH cells are in the robots ? ....
    .

    I have been buying torches (ordinary or headlamps) on Ali exclusively for 18650s for many years, and I have generally tried for many years to ensure that every battery-powered item is 18650 or can be converted to do so (as there has always been free access to these cells from latop batteries or other sources).
    Some automatic cleaning robots have NiMH packs, others are Li-Ion, generally the main reason why such a robot ends up in the scrap yard is because of a dead battery, but otherwise it is usually 100% functional, the same with hoovers or other power tools - dead batteries.
    For example, converting a cleaning robot from NiMH to Li-Ion usually involves adding a 2P4S or 3P4S 18650 pack (2P or 3P in order not to force the cells with too much current) necessarily with an added BMS with built-in balancer (e.g. from Ali 4PLN/unit),
    Energy storage 18650 up to 24kWh class Paragon, Powerwall .
    and the robot's electronics control the current during charging (around usually 600-800mA), i.e. provide a CC charging component and some CV after which the BMS cuts off charging when the rated voltage is exceeded. A balancer built into the BMS ensures that the sections are charged evenly. If you let such a robot out into e.g. a If such a robot is let into e.g. a garage ( I hate cleaning in the garage, therefore I use the robot :) ) to collect all that dirt, filings and sand from the tyres, it is able to run on such a package for hours and even "lick" the floor clean :) .
    When discharged, the BMS will switch off the power supply at the appropriate moment, taking care of the health of our package - so, in fact, even the base of this robot is not needed - it can be charged e.g. with a laptop power supply (also obtained from a scrap yard). You can also add a CC/CV converter to the charger, also from Ali, adjust the CC current and the target voltage - and it will also work without any problems.
  • #139 21584968
    LEDówki
    Level 43  
    Torches - one for D cells or the old fashioned R20. 2 cells... The other was first for a 2S lead acid battery, but has been converted to 3 2/3 AAA batteries plus a balancer. It's been running for about 4 or 5 years. I have another 4xR14 torch, but a damaged bulb holder makes it impossible to use it other than as a night light or blinker. The fixture damaged after being lit for a long time with a krypton bulb instead of a normal bulb. One torch with a 3S lead acid battery and a halogen bulb. Maybe this one I would convert as it has a lot of space inside, but lithium ion batteries in sizes other than 18650 are expensive as they are not that popular. The torches are used either occasionally for trips to the cellar, or a little more often when evenings are short and you have to go to the energy store for fuel.

    The robot is a roomba with a battery of probably 12 SC size batteries. Supposed to be 5Ah, but to the eye it's more like 2.5-3Ah. The batteries are welded together, shrink-wrapped with plastic that fixes the position of the battery in the robot, so the clever otherwise don't put it in the other way round. You can supposedly put 4 lithium ion batteries in there, but the voltages don't match perfectly and I don't want to redo the robot. 30 minutes will go and that's usually enough for one large room. Smaller ones it covers in 10 minutes. It mainly drives on carpets. Smooth floors are handled by a dumb vacuum with a cable.
  • #140 21585425
    yvv
    Level 21  
    >>21565641 .

    I've installed many times temovision cameras on landfill sites which, connected to a recorder, automatically send emails if something in the field of view exceeds a set temperature. Maybe it is worth thinking about such a safety feature? Such cameras are not cheap, but maybe nevertheless. You could also program the output of the camera, or the recorder, to disconnect the cells.
  • #141 21585485
    partyzancik
    Level 24  
    @remzibi And from experience, which cells are most likely to fall off in terms of manufacturers ? Both in terms of temperature rise during charging , self-discharge or loss of capacity ?
  • #142 21585599
    remzibi
    Level 24  
    partyzancik wrote:
    @remzibi And from experience, which cells are most likely to fail as far as manufacturers are concerned ? Both in terms of temperature rise during charging , self-discharge or loss of capacity ?


    Unquestionably the worst crap are LG CHEM.
    But worn out cells are found in all manufacturers, every cell can be accused of improper operating conditions.
    If you want to reuse them, you have to test them thoroughly, depending on the result of the test, reject or allow them to continue working :) .
  • #143 21590247
    robert123
    Level 16  
    I have built on popular gel batteries about 30-40Ah 82V. This works with an Eaton 2.5kW UPS, which is designed to connect external batteries in addition to the internal 9Ah battery.The 2100W Farelka test ran for about an hour.
    The UPS charging can cope with such a battery, but it charges everything with only 1.5 - 2 A. (long).
    Attachments:
  • #144 21595725
    robert123
    Level 16  
    A question from me, did a colleague do a battery test after loading the inverter with the maximum power i.e. 4KW without charging the PV panels at the same time? This would provide nice information (actual battery capacity and inverter efficiency).
  • #145 21596531
    remzibi
    Level 24  
    robert123 wrote:
    Question from me, did a colleague do a battery test after loading the inverter with maximum power i.e. 4KW without simultaneous charging with PV panels? This would provide nice information (actual battery capacity and inverter efficiency).
    .

    No, I did not do typical measurement tests under load.
    On the other hand, yes, it happened to load the installation with up to 4.5kW for a short time, everything worked, but detailed measurement data - no.
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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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