Time spent in absorption.

brewerbrewer Registered Users Posts: 21 ✭✭
I just got the Apex 8D 250 ah batteries.  I have an Outback FX controller.  Their spec sheet does not tell of a suggested time to spend in absorption, which they say should be around 14.6V.  They said to go to the AGM 2 or AGM 1 setting.  I cannot find that in my controller.  I'm looking for starting point to set absorption time.  Anyone have an idea about what that might be?



  • Raj174Raj174 Solar Expert Posts: 764 ✭✭✭✭
    edited January 2018 #2
    The designation AGM 1 and AGM 2 are usually found in PWM controllers. The Outback FM series controllers can be configured to the set points the battery requires. Follow the setup procedure in the attached manual to configure the absorb setting to 14.6 volts and the float setting to 13.5 volts. IMO the charger should be in absorb until the battery is accepting about 6 amps for a 250AH bank. I'd start with 2 hours. The absorb time setting is on page 49.

    Edit to include the MX60 manual and absorb time info.

    Just in case you have the older MX60 model, I have attached that manual also. Absorb time setting is on page 27.

    3600W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 344AH LiFePO4, Kohler Pro 5.2E.
  • mcgivormcgivor Solar Expert Posts: 3,487 ✭✭✭✭✭
    edited January 2018 #3
    In addition to Rick's valuable information, it's important to remember if there are any loads present the end amps feature may be offset by whatever the load draws, generally about 2% of battery Ah capacity is the normal setting, intermittent loads such as a refrigerator cycle so do not generally cause issues, just constant ones. The Absorb timer will terminate the absorption regardless of the end amps setpoint, so the timer setting is largely governed by the arrays capacity to provide enough energy, smaller wattage array  will require more time. In addition seasonal adjustments my be required to compensate for lower output, so it's really a custom setting which must be observed over time to find the sweet spot. FWIW, my controller has a default absorption time of 180 minutes adjustable in custom settings, end amps fixed at 2% of entered battery capacity and recharge at 25v should the float value drop below that setpoint, again custom adjustable. For the most part it works fine at default values but during the rare extended cloudy periods I have, I simply extended the time to 240 minutes, as long as your PV can supply 10% of the rated Ah capacity in charging current these values may be a good starting point.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
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  • brewerbrewer Registered Users Posts: 21 ✭✭
    Thank you Rick and McGivor!
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