Basic Outback vFX Charging Question

n1st
n1st Solar Expert Posts: 77 ✭✭✭✭
The vFX has an absorb (bulk) time limit setting. It this the only means by which it stops charging, or does it have the smarts to sense when the bank is charged, and change to float charge?

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Basic Outback vFX Charging Question
    n1st wrote: »
    The vFX has an absorb (bulk) time limit setting. It this the only means by which it stops charging, or does it have the smarts to sense when the bank is charged, and change to float charge?

    The time limit is a maximum: normally it "counts up" as it goes through the Bulk cycle and then maintains Absorb for however long the Bulk charging took, not to exceed the maximum. So if it reaches Absorb Voltage set point in 1 hour 37 minutes it maintains Absorb for 1 hour 37 minutes. If the maximum is set to 1 hour, it would go to float after 1 hour regardless of the "time left on the clock". The default maximum is 2 hours.

    It also has the ability to stop Absorb at a given current level: Absorb End Amps. This is not the most reliable way to do it as load current will be factored in. Again the time maximum will "over rule" this setting.
  • n1st
    n1st Solar Expert Posts: 77 ✭✭✭✭
    Re: Basic Outback vFX Charging Question

    Thanks for this. Where, may I ask, did you learn this from?

    I see no where in the documentation about a Absorb End Amps - please point me to where I can find this too.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Basic Outback vFX Charging Question
    n1st wrote: »
    Thanks for this. Where, may I ask, did you learn this from?

    I see no where in the documentation about a Absorb End Amps - please point me to where I can find this too.

    :blush:Mia culpa! My mistake: the inverter charger does not have the "end Amps" function, only the charge controllers do. I've tried to fit too many OB manuals into my head. :blush:

    It is not a particularly useful function, as I mentioned before. It is also a good idea to think of your PV charge controller as the "primary" charge source and just use the inverter's built-in charger as a supplementary "as needed" charger (for when the sun doesn't shine).
  • n1st
    n1st Solar Expert Posts: 77 ✭✭✭✭
    Re: Basic Outback vFX Charging Question

    This info really helps. Thanks again.
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: Basic Outback vFX Charging Question

    From manual;

    • The first stage of the charging sequence is the “Bulk” stage. The FX uses as much AC current as possible from the AC input source to raise the battery voltage to the “Absorb” voltage setting. See the “Maximum Current for Battery Charging” heading in the RATINGS section for the FX’s default and maximum values of the AC current used for charging. The time period of the “Bulk” stage will vary with the battery bank’s age, capacity, voltage and AC source.

    • Once the “Absorb” voltage has been reached, the FX will use the necessary AC current to sustain this voltage for the “Absorb Time” (default of 1 hour). The AC current will decrease as the “Absorb” charge continues.

    • After the “Absorb Time Period”, the FX goes into “Silent” mode. The charger is turned off and the FX continues to monitor the battery voltage.

    The bulk period (current limited) will take as long as it needs to get to the absorb voltage setting on the battery. No timer on this phase. (important to set this charge current rate based on your battery size). I think the default setting of maximum inverter charge capability is a bad way to set default on newly installed units.

    The timer starts after the absorb voltage is reached. One to two hours held at the absorb voltage should be enough to fully charge battery.

    The time needed in absorb is dependent on how much current the bulk current limt is set to in relation to batteries AH rating (should set to 12 to 20% of AH in DC amps at battery, Outback regulates based on input AC amps so the conversion to DC amps on battery depends on what battery voltage model used). The higher the bulk current, the lower the SOC wil be when battery reaches a given absorb point (voltage regulated phase). It is also dependent on age of batteries. Older batteries usually need longer absorb time.

    Higher absorb voltage setting will increase the SOC when absorb voltage is reach but too high an absorb voltage setting is hard on the batteries.

    Again, 1 to 2 hours is normal absorb time based on typical recommended bulk current and absorb voltage settings. Outback inverter does not have a termination of absorb based on current taper off during constant voltage absorb period.