Recent content by RCinFLA

  1. RCinFLA

    Does a LiFePo4's charge rating lower as capacity degrades over time?

    As cells age their internal impedance rises. This will mean more cell internal self heating for moderate amount of current, either charging or discharging. It's not the 80% capacity degradation that really hurts. It is the inability to support moderate current loads without significant slump...
  2. RCinFLA

    Different grid-tied inverters in one grid possible?

    If they come close to having proper anti-islanding capability, they should be stackable. Because these are questionable devices that are not legal and potentially dangerous, I would not bet much they have proper anti-islanding A normal GT inverter attempts to wobble its phasing slightly to...
  3. RCinFLA

    Inverter and battery

    No. three-phase GT inverters do not have the capacitors storage cycle reserve for single phase AC current ripple filtering. It is important that ripple current from AC current profile does not show up on PV panels or the panels' efficiency drops.
  4. RCinFLA

    SMA Sunny Boy 7.7 AC coupled frequency watt control tuning

    The freq adjustment control takes too long for an immediate back surge that cannot be handled by hybrid inverter and battery capacity. Freq adjustment power reduction is not triggered until battery voltage exceeds absorb voltage setting. 1) XW has to detect back surge from 60 Hz waveform...
  5. RCinFLA

    SMA Sunny Boy 7.7 AC coupled frequency watt control tuning

    Worst case situation is you are producing a lot of PV power and house loads are consuming most of it. Then someone switches off a heavy load, and all of a sudden XW gets hits with a massive overproduction to deal with. This is where having the ability to pull the PV plug is good thing.
  6. RCinFLA

    SMA Sunny Boy 7.7 AC coupled frequency watt control tuning

    300 AH is small battery for 7kW but you did not state how much actual PV power you are pushing. Obviously you cannot absorb more than XW power rating for maximum charging which is a bit below 6kW. The greater the PV power back push the greater the max battery charge current and the greater the...
  7. RCinFLA

    SMA Sunny Boy 7.7 AC coupled frequency watt control tuning

    Common issue when dealing with two different manufacturers. Sunny Boy was first to put variable power control based on freq shift. Their control was proprietary to their Sunny Island inverter. Originally the industry generic was just a full PV GT or shutdown PV GT. There is suppose to be a...
  8. RCinFLA

    Mixing Lifep04 and Li-Ion

    LG chem are 189ah @ 51.8 volt and the Signature Solar are 100ah @ 51.2 volt LiFePO4. LG Chem cells are likely 14x 4.2v to 3.0v (58.8v - 42.v) operating range. LiFePO4 cells are 16x 3.65v to 2.5v (58.4v - 40v) operating range 51.8v / 3.7v per cell is 14 cells in series. 51.2v / 3.20v is 16...
  9. RCinFLA

    One battery out of 3 behaving different

    Comparing cell voltages at near full charge with no load is pretty meaningless. You are showing cell voltages above 3.45v meaning it has not even been bled of it charging surface capacitance charge. Battery A seems to be more out of balance but without knowing discharge history it is difficult...
  10. RCinFLA

    Hybrid Water Heater

    Approximate numbers for a typical hybrid heat pump hot water heater is it moves 3000 to 4200 BTU'/s per hour for about 500 watts of electric power consumption. A conventional heating element produces about 90% of 3400 btu's per 1000 watts of electric. That is 3060 btu's/hr per kWH. Just...
  11. RCinFLA

    JK (JiKong) BMS - 4S

    That would make poor design sense for it to have anything to do with your system charger being active. Since the BMS is initially off, there will be no voltage on inverter/charger or charger and detecting no battery voltage present they will not apply a charging voltage so BMS would not...
  12. RCinFLA

    JK (JiKong) BMS - 4S

    This statement in the manual, is not technically reasonable and invalidates all their wiring diagrams for 16s and above. "Pls note: the charger voltage must more 4V higher than battery packs, then can make bms power on. Like,your battery is 50v, then your charger must min 54v." Their use of...
  13. RCinFLA

    Sol-Ark 12K vs Outback Radian GS8048a for Reliable Backup

    Outback Radian GS8048a is a low freq inverter. Sol-Ark is a high freq inverter. The Sol-Ark is like two 120vac inverters in series, with each side limited to half inverter ratings. It does not share power between 120vac sides. Outback Radian LF can share a bit of power between sides through...
  14. RCinFLA

    Understanding LIFEPO4 battery terminology and figuring out when its charged...

    Looks like some Chinese to English translation problems in spec. "Max. Permanent Discharge Current = 200A 2secs" should read "Max Permissible Discharge Current = 200 Amps max for 2 seconds max." Nominal voltage is 4 cells for 12v self contained battery x 3.3v nominal per cell = 13.2 v. This...
  15. RCinFLA

    How to keep Lifepo4 cells balanced without charging to 100%

    3.45 v for LFP is fully charged if cell charge current drops to near zero level. When you charge to a higher voltage you are doing so to speed up charging time. When you charge at higher current there will be more kinetic overpotential terminal voltage rise required to support the higher cell...
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