charging battery under load?

javadzjavadz Registered Users Posts: 20
hello ,
if we have an off grid system with a battery that will been charged under load
like if wz are at 09h morning and the load demand about 15A in 1hour,and the panel provide only 5A,assume the battery was fully charged ,normaly the battery will provide the 10A necessrly to the load ,but now if we are at 12h ,and the panels provide 20A ,the 15A will go to the load and the 5A to the battery ,my question is if we use a 100AH capacity of battery,does the charge controler recharge the battery with this 5A or it will need more to begin to recharge the battery?
also ,what is the best algorithm to recharge a battery with load ;is it a 2sategs or the 3stages charging?

Comments

  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Re: charging battery under load?

    The battery will get what is left, the 5A. Whether that is enough depends on its SOC at the start of day, and how long sun you have. In general it doesnt sound like a very balanced system.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: charging battery under load?
    javadz wrote: »
    hello ,
    if we have an off grid system with a battery that will been charged under load
    like if wz are at 09h morning and the load demand about 15A in 1hour,and the panel provide only 5A,assume the battery was fully charged ,normaly the battery will provide the 10A necessrly to the load ,but now if we are at 12h ,and the panels provide 20A ,the 15A will go to the load and the 5A to the battery ,my question is if we use a 100AH capacity of battery,does the charge controler recharge the battery with this 5A or it will need more to begin to recharge the battery?
    also ,what is the best algorithm to recharge a battery with load ;is it a 2sategs or the 3stages charging?

    For short term limited hours power like you get from PV, a three stage charger is probably the best you can get.
    For charging with load, if you have enough panel power, you should get a CC which uses a battery shunt for metering the current in and out of the battery itself. You get two major benefits from that:
    1. You can use a higher amperage CC and panel combination that can provide load and also limit the battery-only current to the right number for the batteries even when there is no load running.
    2. You can have it make the transition between Absorb and Float based on the battery current itself. That will let you drop the batteries back to Float voltage while continuing to supply current to the load.
    SMA SB 3000, old BP panels.
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