Lifepo4 replacement quandary

13

Comments

  • karrakkarrak Posts: 307Solar Expert ✭✭✭✭
    Dave said:
    undefined  I am tired of servicing the LA batteries every month and was hoping that moving to a LiFeO4 system would be a bit more maintenance free, especially to free me up for traveling. I did not realize it would be this complicated. It sounded like with a good BMS and a well-designed system, you can go through the balancing process up front and then be set for a few years, Now, that doesn't sound too  promising.
    As you have said "all you do need is a good BMS and a well designed system". This can be simple if you buy a well integrated system like Schneider gear hooked up to a LG battery or Victron LFP batteries and other Victron gear. It becomes a little harder if you want to use equipment that has not been designed to work with the BMS.
    The simplest way to do this is using a BMS like I have described in earlier posts that is fully self contained and will disconnect the battery if any cell goes out of it safe operating range and will also keep the battery balanced. With this setup if the inverter and charge controller are properly setup and no other fault occurs the BMS should never have to disconnect the battery.
    I am curious about a couple things I've seen here. McGivor is planning on 4 parallel strings. Earlier I have read that a person wants to parallel at most 2 strings, that was for LA batteries, does it not apply to Li?
    I was looking at costs for running 2 strings of 180 or 200Ah batteries versus one string of 400 Ah and they don't seem all that different. Is there any good reason not to run one string of the higher capacity batteries? WOuldn't doing so, greatly alleviate balancing problems because each cell would actually have it's own sensor/balancer?
    I also don't understand why it's considered OK to have a single sensor for two batteries in parallel. It seems to me that both batteries could be off V in different directions and the sensor could indicate that their combined V was correct even though each cell was incorrect.

    You don't wire the cells up as four parallel strings you wire them up as blocks of 4 parallel cells and then make up one string from the blocks of 4 cells. As long as you wire the blocks of 4 cells up so they share the current evenly you won't have any problems.

    When 4 cells are paralleled together they become like one cell because all the individual cell have exactly the same voltage across them. There can be an advantage in having cells paralleled up any variations in the individual cells get averaged out over the paralleled cells.

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 4p8s (24V), 4kW Latronics Inverter, 1160W of Solar Panels, homemade MPPT controller
    Homemade BMS https://github.com/simat/BatteryMonitor
     

  • westbranchwestbranch Posts: 5,090Solar Expert ✭✭✭✭
    When/where did you get yours, it seems the inventor has dropped out of sight...??
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • mcgivormcgivor Posts: 2,226Solar Expert ✭✭✭✭✭
    @BB said
    I also have a concern with hacking the temperature sensor to drop output voltage on the Charge Controller in the event of an overcharge. It sort of depends on what is happening with the Solar Charge controller... If the computer lost its mind, then adjusting the temperature sensor will probably not stop the over charging. Also, since charge controllers usually have a series pass transistor of some sort (between the solar array and the battery bank), a failed (shorted) transistor would not be affected by a temp-sensor hack shutdown circuit.

    Actually this is a recommended method by Morningstar at least for their controllers, they explain this in detail  here's  a link https://www.morningstarcorp.com/morningstar-best-practices-battery-chemistry/
    they also state it can be done with software. The shutting down of the battery is also discussed which Simon @Karrak, or anyone else for that matter, may find informitive, I'm assuming this information relates to their equipment, as they cannot speak for others. 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • mcgivormcgivor Posts: 2,226Solar Expert ✭✭✭✭✭
    @Dave said, Speaking to Auto Parts Electric, it sounded like it was not a huge deal to make the change to Li, i.e. one did not have to be an electrical engineer to do a good job on a system. Was I being led down the primrose path or are posters here just holding their systems to a higher standard?

    There are drop in replacement LiPo4 batteries with intrergated BMS, that could be what is being referred to, there are also larger battery packs available, usually sealed units made up of many small cells in many cases, choosing to go the build it yourself route dose require some work and research to ensure success, that's the stage I'm currently in, the open cell arrangement allows one to be able to at least test individual cells with a meter to confirm the BMS values, replace a bad cell, add or reduce capacity as needed, one has to weigh in all the factors before making a decision IMHO. 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • DaveDave Posts: 28Registered Users ✭✭
    > @mcgivor said:
    > @Dave said, Speaking to Auto Parts Electric, it sounded like it was not a huge deal to make the change to Li, i.e. one did not have to be an electrical engineer to do a good job on a system. Was I being led down the primrose path or are posters here just holding their systems to a higher standard?
    >
    > There are drop in replacement LiPo4 batteries with intrergated BMS, that could be what is being referred to, there are also larger battery packs available, usually sealed units made up of many small cells in many cases, choosing to go the build it yourself route dose require some work and research to ensure success, that's the stage I'm currently in, the open cell arrangement allows one to be able to at least test individual cells with a meter to confirm the BMS values, replace a bad cell, add or reduce capacity as needed, one has to weigh in all the factors before making a decision IMHO. 

    thanks @mcgivor but this was individual batteries and a separate designed to work on a system of that size and characteristics. i wanted to avoid an all-in-one system for the reasons you mentioned, thanks.

    I'll try and remember which bms raj recommended and post it.

    i am still curios pros/cons of multiple strings versus bigger capacity batteries in single string. one negative for the latter would be greater expense if a battery failed. others?

    we don't need huge reserve, 350 usable Ah would be plenty so either option should be viable i think.
    12 * 300 W (10 fixed rooftop, 2 movable pole mount), Morningstar Tristar MPPT 60, Magnum 4448 PAE, 16 Crown CR-235 6V in two parallel sets of 8 (470 Ah)
  • DaveDave Posts: 28Registered Users ✭✭
    i meant "separate bms" but left out bms.
    12 * 300 W (10 fixed rooftop, 2 movable pole mount), Morningstar Tristar MPPT 60, Magnum 4448 PAE, 16 Crown CR-235 6V in two parallel sets of 8 (470 Ah)
  • mcgivormcgivor Posts: 2,226Solar Expert ✭✭✭✭✭
    edited August 5 #68
    When you are looking for all in one solution I believe this fits.
    The Electrodacus looks to be a solution, only problem is they seem unavailable, last website information is dated 2016, last Facebook post Jan 2017.

    Edit. Took the time today to email Dacian, the developer of the ElectroDacus to ask the question if he was still in business this was his reply 

    I currently have no stock of SBMS but I will do another Kickstarter around the end of this month or early next month and if that is successful I will build another batch around the end of the year.
    For details you can check the user manual here http://electrodacus.com/SBMS120/manual/SBMSmanual.pdf
    And latest news on my google+ page here https://plus.google.com/+electrodacus

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • mcgivormcgivor Posts: 2,226Solar Expert ✭✭✭✭✭
    @Dave The choice of smaller cells was mainly due to price per Ah, as Simon points out post #62 it really doesn't matter as the parrallel cells are in blocks so essentially single cells.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • just startingjust starting Posts: 221Registered Users ✭✭
    I could possibly sell you one I have 3 of each, one of each right now, I'm waiting on the dmppt450
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
  • karrakkarrak Posts: 307Solar Expert ✭✭✭✭
    BB. said:
    Solar Charge Controllers do not really regulate voltage (on short time scales)--The battery bank does the major voltage regulation (buffering current).

    When you disconnect the battery bank, but (for example) leave the DC loads still connected and running, it is certainly possible for the DC bus (without battery) to go out of regulation (high or low, or, hopefully directly to OFF).
    For standard operational conditions I agree that the battery plays a large part in the voltage regulation and that the standard charge controller voltage regulation mechanism would probably be too slow to react to the battery being suddenly disconnected. If the output voltage rises to a point where it would damage circuitry within the charge controller there should be an internal emergency shutdown mechanism which would immediately (in a matter of microseconds) shutdown any power coming from the solar panels.

    I had a look a quick look at the operation manuals for the Tristar MPPT controllers which warns that damage can be done to the controller if the battery is disconnected while charging, the Outback Flexmax manual doesn't say anything and gives no warnings and the  Schneider Conext manual give this rather encouraging message.

    "If the solar charge controller is charging when the batteries are disconnected
    with a DC disconnect switch, an over-voltage output fault occurs due to the load
    on the solar charge controller output being removed. After approximately 10
    seconds the solar charge controller LCD goes blank and the solar charge
    controller loses power.
    Normal operation resumes when the battery is reconnected."

    Simon


    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 4p8s (24V), 4kW Latronics Inverter, 1160W of Solar Panels, homemade MPPT controller
    Homemade BMS https://github.com/simat/BatteryMonitor
     

  • karrakkarrak Posts: 307Solar Expert ✭✭✭✭
    Dave said:
    i am still curios pros/cons of multiple strings versus bigger capacity batteries in single string. one negative for the latter would be greater expense if a battery failed. others?

    I think 2PxS is a good configuration as it means you still have a working battery if one cell goes open circuit or looses capacity. It also means that you can easily expand the battery size by 50% rather than doubling it if you wanted to.

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 4p8s (24V), 4kW Latronics Inverter, 1160W of Solar Panels, homemade MPPT controller
    Homemade BMS https://github.com/simat/BatteryMonitor
     

  • just startingjust starting Posts: 221Registered Users ✭✭
    edited August 5 #73
    Karrak Wow a 720 ah Winston bank I'm so jealous.Or is it 360?
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
  • karrakkarrak Posts: 307Solar Expert ✭✭✭✭
    It is a [email protected], soon to be [email protected] or around 9.3kWh battery. Enough to run the household including cooking.

    Big improvement on the old NiCd battery I used to own!

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 4p8s (24V), 4kW Latronics Inverter, 1160W of Solar Panels, homemade MPPT controller
    Homemade BMS https://github.com/simat/BatteryMonitor
     

  • Dave AngeliniDave Angelini Posts: 4,023Solar Expert ✭✭✭✭
    That should get you around 10KWH Simon. Very nice!  The Resu I have is about 9 useable and is perfect for us. I would not mind more but for 2 years it has been the cats meow. Still 99% Sol and we have been seriously cycling in this wild fire for nearly a month.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • mcgivormcgivor Posts: 2,226Solar Expert ✭✭✭✭✭
    The search for a BMS has been tedious, primarily due to the specifications needed, 60A charge 110A discharge, most seem poorly made, based on images, with no heat sink or actual terminals, the one settled on is in attached pdf, any thoughts? 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • karrakkarrak Posts: 307Solar Expert ✭✭✭✭
    Were you planning on separate charge and discharge disconnects?

    Lack of heat sinks can actually be a sign of using MOSFTES with lower resistance and thus not needing the large heat sinks.

    "From the voltage drop I measured I calculated the drain source resistance of the original HY3008 FETs to be ~7mOhms, so total resistance of the ten FETs in parallel is 0.7mOhms. This gives a power loss of ~7W with a 100A load."

    The board you are looking at says the MOSFET resistance is <20mOhms.

    Simon


    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 4p8s (24V), 4kW Latronics Inverter, 1160W of Solar Panels, homemade MPPT controller
    Homemade BMS https://github.com/simat/BatteryMonitor
     

  • mcgivormcgivor Posts: 2,226Solar Expert ✭✭✭✭✭
    Wouldn't the number of mosfets have an influence over the overall power loss, it appears to have 56 in total, how they are configured is an unknown, to me at least, this is a new avenue of learning on my behalf.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • mcgivormcgivor Posts: 2,226Solar Expert ✭✭✭✭✭
    With regards to separate disconnects, the manufacturer will send all wiring information, so I'll take it from there when it arrives as part of a samples package, not sure what's included but the price is right.
    Ivor 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • karrakkarrak Posts: 307Solar Expert ✭✭✭✭
    To stop current in both directions you need two FETs back to back in series as per my earlier post
    From the pictures in the pdf you linked to I would say that there is a total of 48 FETS in two blocks of 24.

    Each block of 24 FETs are wired in parallel so the resistance of each block would be ~0.8mOhms. The two blocks are wired is series so the total resistance is ~1.6mOhms.

    If you split the FET switch into two halves, one blocking the charge current and one blocking the discharge current the current only has to go through one set of FETs so it halves the power dissipation.

    Other issues I see with this board are that the connect, disconnect and balance voltages are not programmable and that there is no display or output to a mobile phone or computer so there is no way for you to easily monitor the cell voltages and battery current.
    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 4p8s (24V), 4kW Latronics Inverter, 1160W of Solar Panels, homemade MPPT controller
    Homemade BMS https://github.com/simat/BatteryMonitor
     

  • mcgivormcgivor Posts: 2,226Solar Expert ✭✭✭✭✭
    The lack of display and programming ability were questions asked, that's when the question of testing samples was brought up by the seller, couldn't look a gift horse in the mouth, it would be better than nothing, would you not agree.

    Ivor 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • westbranchwestbranch Posts: 5,090Solar Expert ✭✭✭✭
    Ivor, where did you find the extra detail, Model posted is not even listed on their site??
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • DaveDave Posts: 28Registered Users ✭✭
    mcgivor said:
    The lack of display and programming ability were questions asked, that's when the question of testing samples was brought up by the seller, couldn't look a gift horse in the mouth, it would be better than nothing, would you not agree.

    Ivor 
    , it sounds like you already have a path but I am curious what you and Simon think of this option for 24V:


    12 * 300 W (10 fixed rooftop, 2 movable pole mount), Morningstar Tristar MPPT 60, Magnum 4448 PAE, 16 Crown CR-235 6V in two parallel sets of 8 (470 Ah)
  • bill von novakbill von novak Posts: 784Solar Expert ✭✭✭✭
    karrak said:
    mcgivor said:
    The use of mechanical relays to disconnect charge and discharge, as apposed to internal mosfets, or other means, would make it reletivaly easy to include a second BMS simply as a monitor of the primary system, interlocked via a second contact in the relay coil circuit. Perhaps I'm over thinking this a little,  but redundancy is not nesesarally a bad thing.

    The one problem with using mechanical relays is that they use quite allot of power. F
    Not if you use a latching relay.
  • mcgivormcgivor Posts: 2,226Solar Expert ✭✭✭✭✭
    Ivor, where did you find the extra detail, Model posted is not even listed on their site??
    What I've done in my search  process is ask questions,  providing all relevant information pertaining to my basic requirements,  voltage,  battery capacity and charge/discharge current. Based on this they provide suggestions, then I ask for more details, monitoring ability and so forth, very tedious, some sales staff are quick to answer, other say they need to consult thier engineering department before answering, those are the ones I tend to be more interested in, after all engineers most likely don't answer sales questions directly, unless a one person operation. This particular company didn't have a product filling all my required needs but explained they were confident in their product and offered samples to test and evaluate. They do appear to be a larger OEM supplier which may have products other than those listed on their website, over 200 pages worth, for what that's worth, so in the end I'm only out  of pocket for shipment and will continue to research as I progress.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • DaveDave Posts: 28Registered Users ✭✭
    nevermind my last post, i was reading up and this PMC really doesn't do the same job as a BMS.
    12 * 300 W (10 fixed rooftop, 2 movable pole mount), Morningstar Tristar MPPT 60, Magnum 4448 PAE, 16 Crown CR-235 6V in two parallel sets of 8 (470 Ah)
  • karrakkarrak Posts: 307Solar Expert ✭✭✭✭
    Dave said:
    nevermind my last post, i was reading up and this PMC really doesn't do the same job as a BMS.
    I am puzzled, it looks like a BMS to me,does all the functions of a BMS
    • Monitors individual cell voltages and charging current
    • Will disconnect battery if cell voltages or charge/discharge current goes out of operational limits
    • Will keep the battery balanced.
    I think it will also output this information to a computer but am not sure about this. Am I missing something?

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 4p8s (24V), 4kW Latronics Inverter, 1160W of Solar Panels, homemade MPPT controller
    Homemade BMS https://github.com/simat/BatteryMonitor
     

  • DaveDave Posts: 28Registered Users ✭✭
    > @karrak said:
    > Dave said:
    >
    >
    > nevermind my last post, i was reading up and this PMC really doesn't do the same job as a BMS.
    >
    >
    >
    >
    >
    >
    > I am puzzled, it looks like a BMS to me,does all the functions of a BMS
    >
    >
    > * Monitors individual cell voltages and charging current
    > * Will disconnect battery if cell voltages or charge/discharge current goes out of operational limits
    > * Will keep the battery balanced.
    >
    > I think it will also output this information to a computer but am not sure about this. Am I missing something?
    >
    >
    >
    >
    > Simon

    it makes me feel better that you're confused! they don't call it a bms and i don't know why. it's a less expensive option to their bms
    https://www.electriccarpartscompany.com/3V-1S-Lithium-Lighted-Battery-Balancers

    but i am struggling to work out what it lacks in comparison because, as you say, it seems pretty comprehensive.

    i need to call them again.
    12 * 300 W (10 fixed rooftop, 2 movable pole mount), Morningstar Tristar MPPT 60, Magnum 4448 PAE, 16 Crown CR-235 6V in two parallel sets of 8 (470 Ah)
  • karrakkarrak Posts: 307Solar Expert ✭✭✭✭
    The part you linked to is not a BMS, it is the part of the BMS that will balance the battery but will not provide any protection if any cell goes out of its safe operating zone. Using just these balancing circuits alone can give a false sense of security and I am sure have lead to a few if not many damaged batteries.

    If you do call them can you ask them
    1. If  you as a user can connect the BMS up a computer and what is needed to do so.
    2. Is there an App for the computer that will allow you to monitor the cell voltages, battery current and temperature in real time
    3. Is it possible for the user to reprogram the configuration on the BMS
    SImon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 4p8s (24V), 4kW Latronics Inverter, 1160W of Solar Panels, homemade MPPT controller
    Homemade BMS https://github.com/simat/BatteryMonitor
     

  • karrakkarrak Posts: 307Solar Expert ✭✭✭✭
    edited August 8 #90
    karrak said:
    mcgivor said:
    The use of mechanical relays to disconnect charge and discharge, as apposed to internal mosfets, or other means, would make it reletivaly easy to include a second BMS simply as a monitor of the primary system, interlocked via a second contact in the relay coil circuit. Perhaps I'm over thinking this a little,  but redundancy is not nesesarally a bad thing.

    The one problem with using mechanical relays is that they use quite allot of power. F
    Not if you use a latching relay.
    To my knowledge the problem is that latching relays need some sort of special interface to operate and make sure they have worked correctly. I have used a latching relay to disconnect the PV panels on one of the systems I have installed. It is being controlled via software I wrote on a Beaglebone Black microcontroller board.

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 4p8s (24V), 4kW Latronics Inverter, 1160W of Solar Panels, homemade MPPT controller
    Homemade BMS https://github.com/simat/BatteryMonitor
     

  • Dave AngeliniDave Angelini Posts: 4,023Solar Expert ✭✭✭✭
    Latching relays would have to be robust to support over 100A for a large system. I have never seen one that large. One would still need a way to know it worked unattended. I suppose if you monitor power to the house you would know ;)
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

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