Which charge voltage to use with Outback FX?

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Dan_
Dan_ Solar Expert Posts: 61 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
I have 8 Costco/Interstate GC2-HD in series charging via generator and FX3048. According to manufacturer spec the batteries get charged to 80% at 7.2v and from there 7.65v to 95% then float to 100. FX is not sophisticated enough to charge this way though. Just has absorb and float.
Should I simply charge at 7.65? I have thus far been playing it safe and charging at 7.2 but I do indeed find that the batteries only get to 80%

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: Which charge voltage to use with Outback FX?

    RE systems do not run the same as utility charging because they don't have full power available for an unlimited amount of time. These battery specs are meant for utility charging as they never were intended for RE use. So you have to go with the lower Voltage defaults, check charging performance, and adjust to where you get best results.

    Set the Absorb Voltage to the 7.2 multiple: 57.6 on a 48 Volt system. Increase to 59.2 if needed. Do not use the 7.65 multiple as the amount of time spent in Absorb will probably be long enough to boil them dry (excess water use). Ignore the concept of charging during Float. You can set a fairly high Float Voltage (55.2 Volts say) but you may find it impractical to achieve/sustain from generator power (no one wants to run the gen to supply small amounts of charging - it just wastes fuel).

    If you are not getting full SG increase Absorb time if possible. If that still doesn't do it increase Voltage in 0.2 V increments. Unfortunately these batteries are meant for high Voltage 'penultimate' charging and that makes them rather impractical for RE.

    Remember for gen charging you really only need to get the batteries above 75% SOC to be efficient; the sun should come out some day and do a proper 100% charge. These Voltage set points would apply to solar charging too.
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  • Dan_
    Dan_ Solar Expert Posts: 61 ✭✭✭✭
    #3
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    Re: Which charge voltage to use with Outback FX?

    Much appreciation for your reply

    Upon further monitoring of the voltage while charging it seems the Outback charger is smarter than I thought. It ramps up the voltage as the charge progresses eventually hitting the absorb setpoint where it then backs off on the current but keeps the voltage for a set time period. Charge has gone well so far with 61.2v absorb setpoint and no significant water loss but I'm closely watching the levels

    Unfortunately I have a very temp setup at the moment living in a trailer and no solar yet. Just very expensive gasoline. Just running a cheat fridge and occasional well pump
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #4
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    Re: Which charge voltage to use with Outback FX?
    Dan_ wrote: »
    Charge has gone well so far with 61.2v absorb setpoint and no significant water loss but I'm closely watching the levels

    That's too high for a daily charging voltage. It's OK for a few days to bring your batteries back to 100% SOC, but I wouldn't do it daily unless you are very deeply cycling the batteries every day.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: Which charge voltage to use with Outback FX?
    Dan_ wrote: »
    Much appreciation for your reply

    Upon further monitoring of the voltage while charging it seems the Outback charger is smarter than I thought. It ramps up the voltage as the charge progresses eventually hitting the absorb setpoint where it then backs off on the current but keeps the voltage for a set time period. Charge has gone well so far with 61.2v absorb setpoint and no significant water loss but I'm closely watching the levels

    Unfortunately I have a very temp setup at the moment living in a trailer and no solar yet. Just very expensive gasoline. Just running a cheat fridge and occasional well pump

    Not exactly.
    As charging progresses Voltage of the batteries increase. This is how it works for all chargers.
    Once Absorb is reached current reduces as the battery charges. Again, this is how charging works.

    vtMaps is correct that 61.2 is too high an Absorb Voltage. Note I stated in my first post it can be as high as 59.2. Turn it down; you are subjecting the batteries to excessive heating. >60 Volts is EQ level.
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