battery question

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petertearai
petertearai Solar Expert Posts: 471 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
Hi My solar system typically is used only at the weekend.I note on the outback fm80 log that while Im not there around 30 ah each day is produced but bats are full and zero load except for the battery monitor. Is this normal ?
Regards peter
2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #2
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    Re: battery question

    Don't know your battery size / voltage etc, but it could well be normal as each day the controller will strive to bring the bat voltage up to the point (and time) required for the switch to float mode, and that takes amp hours.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #3
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    Re: battery question

    Is this a flooded cell battery bank? How much water do you add? Roughly, needing to add water about every two months would be a good aim point... Adding water every month or more often would indicate that batteries are probably being overcharged.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
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    Re: battery question

    It is perfectly normal for some charging to occur whether or not there is any battery usage. How much would be dependent on the factors Wayne mentioned. Too much would be indicated by excess water usage as Bill mentioned.

    The Outback will "wake up" every day, try to charge, run through a quick Bulk cycle followed by and equally short Absorb cycle, then slip in to Float for as long as it can be maintained. Once solar drops to the point where Float can't be maintained the charger controller may try to re-bulk, depending on resting Voltage of the batteries and how the FM is programmed. Obviously this will result in some charging being logged.
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  • petertearai
    petertearai Solar Expert Posts: 471 ✭✭✭✭
    #5
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    Re: battery question

    Thanks for your replys .My system is 770 watts pv 900 ah rolls surette batts 4 times 6 volt wired for 12 volts.About to add 2 more bp 125 pv as Ive learned ( from this site) that my pv is still a little low.I do add water if I haven't been there for 2 to 3 weeks but not measuring how much.How do you measure the amount, and how much is more than normal? I have absorb set to 3 hours at 14.4 volts, have yet to have the patience to watch the amps get to an even low point amps to set the controller to end amps.
    Thanks for the wonderful advice that is provided by all you responders
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,019 ✭✭✭✭
    #6
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    Re: battery question

    Just get the batteries electrolyte level 1/4 to 1/2 inch below fill neck bottom, then the next time you fill use a 250ml (1 cup) measuring cup. Top up the level and figure out how much you used from the cup. No need to be accurate to the 1ml level because it's hard to get the 1/4 to 1/2 inch accurately measured anyway...Mark 1 eyeball has it's limitations. After you've done this for a while you'll expect the same top up amount each time, but still watch the level, you don't want to overfill.

    I found problem cells not just by SG readings, but by change in water replenishment amounts too. Cells since replaced by Surrette. Shipping to NZ would be a tough nut.

    Ralph
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