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  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...
  16. RCinFLA

    Soft Starters for Air Conditioners

    Your modification would triac voltage ramp both the compressor and fan. It may result in startup problems with fan motor as there will be no larger start cap during voltage ramp.. MicroAir also has a four or five second delay after main contactor closes from thermostat control before...
  17. RCinFLA

    ATS causing power surge inverter damage.

    Any transfer switch that switches between two non-syncronized AC sources needs to have time delay between connections. Per their ad they claim inverter transfers to utility power ≤10ms, and utility power transfers to inverter ≤16ms. This is basically the time it takes for a mechanical relay to...
  18. RCinFLA

    How does an inverter synchronise to a generator?

    For a synchronous generator (a 3600 rpm, 60 Hz generator), if it has engine varying in rpm due to an unstable rpm govenor, its causes its AC output frequency to vary. This can be a problem for inverter to track. A sudden heavy load surge on generator requires the carborator throttle to be...
  19. RCinFLA

    How does an inverter synchronise to a generator?

    Its a drawing I did. Here it is in PDF.
  20. RCinFLA

    How does an inverter synchronise to a generator?

    You are referring to a battery equipped hybrid inverter that accepts AC input from grid or generator. Hybrid inverter has inverter permanently connected to AC output. There is a connect relay between AC input and inverter. Relay is normally open. When an AC input voltage is detected and...
  21. RCinFLA

    Schneider xw pro 6848 not powering up with eg4 lithium battery

    That would not be a good solution for a number of reasons. Where do you get the power to precharge the caps for off grid setups, and what consequences arise from having inverter DC input terminals with charged large capacity capacitors.
  22. RCinFLA

    Schneider xw pro 6848 not powering up with eg4 lithium battery

    There are a lot of BMS's out there that will shut down for overcurrent when attempting to charge the inverter input caps. I will give EG4 battery packs credit for attempting to design a solution for this common problem but it is difficult when you have to deal with a myriad of different...
  23. RCinFLA

    Schneider xw pro 6848 not powering up with eg4 lithium battery

    If you did the manual precharge your problem would have gone away,
  24. RCinFLA

    Schneider xw pro 6848 not powering up with eg4 lithium battery

    If the battery pack has an inverter cap charge surge system it must act on timing. It initially triggers like a a true short circuit has occurred opening up the BMS's main series MOSFET's but connecting a separate single MOSFET, or mechanical relay in series with power resistor. If short is...
  25. RCinFLA

    Water Drops Inside Lifepo4 Battery Case

    Whenever a container is sealed well, unless the air inside was flushed with dry gas like dry nitrogen, there will be water vapor trapped in the air. I do not expect it is usual for the inside of self contain 12v LFP battery case to be flushed with dry gas but if the battery was assembled in a...
  26. RCinFLA

    EVE-280 cells should these be clamped tight or spaced for expansion?

    Compression is intended to suppress delamination, primarily the aluminum and copper foil from their respective LFP and graphite screen printed material. Electrode delamination from metal foil is more likely to happen when there is more temp cycling of cell due to temp expansion coefficient...
  27. RCinFLA

    EVE-280 cells should these be clamped tight or spaced for expansion?

    This chart is creating much mis-interpretation and in my opinion is borderline fraud. First, it specifies at 1 CA. What is not directly mentioned is their compression fixture must also be providing cooling for cell. At 1 CA discharge/charge rate the cell internal self heating will be 32 to 40...
  28. RCinFLA

    Behavior while AC running in heater mode

    With 480 AH lead-acid batteries you should not be having problems with 35 amps of load current. If batteries are fully charged and in good conditions you should be able to easily get 7 hours of run time for 70% discharge of batteries. I derated AH rated capacity to 75% (360 AH) for 35 amp load...
  29. RCinFLA

    Behavior while AC running in heater mode

    You likely have not set the battery capacity size in setup. Also there is a setup for peak charge voltage where monitor resets itself to 100%. You also have a setup for charge efficiency. For LFP batteries set charge efficiency for 99%. Many monitors default charge efficiency to about 85%...
  30. RCinFLA

    Do you need to balance Lifepo4 batteries in series?

    The desired state is all of the parallel stacks contribute equally to the current the inverter is drawing. Even with same batteries bought at same time they will not perfectly match. You should have less than 20% current imbalance between the parallel stacks however. Several reasons why they...
  31. RCinFLA

    Do I(we) need UL1741?

    If you are off grid UL1741 does not have much meaning to your system. It is specifications for connecting an inverter running in parallel with grid. Primarily rules for detecting when grid goes down so your inverter does not push power to grid, possibly energizing a downed power line.
  32. RCinFLA

    Big inverters vs smaller inverters- power usage.

    The dominate idle consumption on inverters should be caused by the power consumed switching the high frequency power MOSFET gate input capacitance. The larger the inverter VA rating, the greater the sum total of MOSFET input capacitance to chop on and off. There are a couple of other things...
  33. RCinFLA

    Experience purchasing cells from Shenzhen Basen Technology Co. Ltd.

    51 mV slump @ 40 amps is a good number for a new cell value. (y) There is PC software for the EB tester you can download that will record the tabular data numbers to a file. Very good to keep the data so you can check cell performance again at a later date and compare it to original new cell...
  34. RCinFLA

    Experience purchasing cells from Shenzhen Basen Technology Co. Ltd.

    For 280 AH EVA's I expect about 45-50 mV slump for 40 amp discharge on a new cell. Older used cells can be 3 to 5 times greater so load test is also a good quick way to see if you got screwed by vendor sending you used batteries. These higher slump voltage cells will not make their rated...
  35. RCinFLA

    Experience purchasing cells from Shenzhen Basen Technology Co. Ltd.

    Yes, that arrangement is going to give you a little lower voltage reading for the sense voltage than actually on the battery terminals. When you want to detect 5-10 mV cell voltage difference with loading every little detail counts.. Would be a little better if you can get voltage sense...