Should I set float to 56 volts?

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softdown
softdown Solar Expert Posts: 3,821 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
I use eight 270Ah 12 volt AGM batteries by Fullriver, Due to the AGM chemistry and size of bank, I'd like a much longer 58.4 volt absorb cycle. The factory setting is two hours on the Outback FM80. Efforts to change the length of the absorb cycle were fruitless. I pushed a lot of buttons to no avail. Reprogramming high tech push button stuff is as likely to give me the heebie jeebies as success. I didn't grow up programming electronics, I grew up hiking. biking,  and playing tennis. Thats my excuse and I'm sticking to it. 

I could change the voltage on the float cycle though. Changing it from 54.4 to 56 is not ideal but I suspect it would do more good than harm. 
Thoughts? 
First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #2
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    At this point, especially since we are heading into shorter days... 56.0 volts (14.0 volts @ 12 volts) would be a good start.

    Monitor the charging current to the bank (after it has sat on charge/float for many hours), and see what the current is... I am guessing, but if the bank is down to 0.1% of bank AH capacity (400 AH becomes 0.4 amps of float charging)--You are not hurting anything.

    I have never had a Outback controller in my hands, but have you hit the "save" or "write" button? Many of these controllers will let you edit the value but will not commit to non-volatile memory without doing a configuration save/write. (again, just guessing)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • softdown
    softdown Solar Expert Posts: 3,821 ✭✭✭✭
    #3
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    Somehow stumbled into the Advanced Menu this time. Very easy from there. Absorb time was 1 hour. Now set at 4 hours. Thanks to BB for getting me to persevere. One hour? Sheesh. Thought things looked fishy with how quickly it went to Float. 
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
    · Share on Twitter

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