Lifepo4 replacement quandary

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Comments

  • BB.BB. Posts: 27,684Super Moderators admin
    Bluesea has some latching relays upwards of 500 amps at 12 and 24 volts... May be expensive in the ~$250 USD range. These are designed to connect battery banks when charging--May need "hacking" for the disconnect function/control.

    https://www.bluesea.com/products/category/35/Automatic_Charging_Relays

    250 Amp latching solenoid:

    https://www.bluesea.com/products/9012/L_Solenoid_-_12_24V_DC_250A

    -Bill


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Posts: 3,886Solar Expert ✭✭✭✭
    Cool might help someone. For my money, this needs to all be done and tested by the people who build the battery.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • 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

    I called Electric Car Parts (ECP) today but unfortunately I had not seen this post so I didn't ask these questions. But, here's some explanation:
    The Protective Circuit Board management system (https://www.electriccarpartscompany.com/48V-512V-576V-Custom-Built-Lithium-LiFePO4-LFP-PCB-PCM) only had 70 mA available to balance so if there is much V discrepancy, it would take a very long time to correct. The battery balancer he recommended (https://www.electriccarpartscompany.com/3V-1S-Lithium-Lighted-Battery-Balancers) has 6 A to do the job.
    The setup he recommends is a battery balancer for each cell (16 for me) and then a battery manager (https://www.electriccarpartscompany.com/48V-100A-EV-BMS-Battery-Management-System) for the system. The BMS would provide the disconnects and do large scale balancing of the bank.

    Looking at ivor's earlier post it sounded like he was getting a battery bank for $2k (24V 400Ah as I recall) and that's a lot cheaper than it would cost thru ECP from what I could tell. That may apply to other components too. For some reason, I am nervous about ordering from Ali. For one thing, if there is a warranty issue, would you try to handle through them or the manufacturer? I suppose if you save enough on hte order, you could apply the savings to new components if that was easier than trying to get warranty coverage.




    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: 2,052Solar Expert ✭✭✭✭
    The batteries arrived today, a week from order date, not bad.
     @Dave said. For some reason, I am nervous about ordering from Ali. For one thing, if there is a warranty issue, would you try to handle through them or the manufacturer? I suppose if you save enough on hte order, you could apply the savings to new components if that was easier than trying to get warranty coverage
    At first i was a little  apprehensive about Alibaba, perhaps the Ali Baba thieves association  :D , but in reality they act as a go between offering protection to the buyer by holding funds from the seller  until the transaction is complete and the customer is satisfied. When I imported cars from Japan to Canada I used a similar trade assurance company in Japan, as protection from shady operators. All my dealings  so far with Alibaba have been positive.


      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • karrakkarrak Posts: 304Solar Expert ✭✭✭✭
    Dave said:
    But, here's some explanation:
    The Protective Circuit Board management system (https://www.electriccarpartscompany.com/48V-512V-576V-Custom-Built-Lithium-LiFePO4-LFP-PCB-PCM) only had 70 mA available to balance so if there is much V discrepancy, it would take a very long time to correct. The battery balancer he recommended (https://www.electriccarpartscompany.com/3V-1S-Lithium-Lighted-Battery-Balancers) has 6 A to do the job.
    The setup he recommends is a battery balancer for each cell (16 for me) and then a battery manager (https://www.electriccarpartscompany.com/48V-100A-EV-BMS-Battery-Management-System) for the system. The BMS would provide the disconnects and do large scale balancing of the bank.

    Looking at ivor's earlier post it sounded like he was getting a battery bank for $2k (24V 400Ah as I recall) and that's a lot cheaper than it would cost thru ECP from what I could tell. That may apply to other components too. For some reason, I am nervous about ordering from Ali. For one thing, if there is a warranty issue, would you try to handle through them or the manufacturer? I suppose if you save enough on hte order, you could apply the savings to new components if that was easier than trying to get warranty coverage.
    If the cells are all reasonably balanced to start with the high rate 6A balancers will be unnecessary. From the pictures the 48V-100A-EV-BMS-Battery-Management-System looks like it has a balancing function but the balance current would probably be around 70mA as well. Doesn't look like you can connect it to the outside world and it doesn't have a display.

    One function that a BMS should provide which is extremely useful is the SOC of the battery (battery fuel gauge).

    As for ordering from Ali I have ordered many different things from different suppliers and have never had any problems. I think Ali will help you if the goods don't arrive, are DOA or not as advertised but you are probably on your own if things go pear shaped a few months down the track. I always do an Internet search on the supplier and the product to see how much feedback there has been. For Lithium batteries and BMSes I suggest you have a look at the Endless Spheres Forum

    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
     

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