Recommendations please

offgrid
offgrid Registered Users Posts: 20 ✭
in Solar Beginners Corner #1
Wondering what value to give the "absorb end amp" it is currently set at 0 (by default). If you have links to discussion that would be great too.

Thanks !
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #2
    Re: Recommendations please

    What does your battery manufacturer recommend for your model of batteries (if anything)? AGM? Flooded Cell? Some other type?

    How are the batteries used? Heavy usage every day with solar charging. Or do they sit for long periods of time (i.e., summer cabin use)...

    If the batteries are cycled daily and recharged by solar--the absorb ending (transfer to float) probably does not change much for you.

    If the batteries are lightly used or sit for long periods of time (charged in the first couple of hours of sun, or sit for 1 month or more unused)--then I would tend towards a more aggressive transition point from aborb to float. You don't want the batteries sitting at 14.4 volts (12 volt example) for hours at a time (two hours seems to be a good default).

    I am not the expert, but when charging current drops to 10% of max charging current is probably a good time to start the absorb timer (assuming your charging current is somewhere around 5%-13% or so of Battery 20 Hour capacity).

    For periods of storage--setting the absorb timer to zero hours and an immediate transition to float would help the battery last longer and use less water (when you are not there).

    Assumes that you do monitor electrolyte specific gravity and bank charge levels--and do an equalization (assuming flooded cell) every 1 month or so (typical range around here seems to be every 2-8 weeks based on battery condition and personal preferences).

    Trojan recommends equalization (of flooded cell batteries) when SG differences between cells exceed 0.030

    AGM's should never be equalized like a flooded cell battery (can quickly ruin the AGM battery if over charged)... However, holding a high absorb voltage a couple times a year for a few hours has been helpful for battery life (recent findings have found AGM cells can get "out of balance" too).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • blackswan555
    blackswan555 Solar Expert Posts: 246 ✭✭
    #3
    Re: Recommendations please

    Where are you seeing this setting ? In the mate ? You do not list a FNDC so it is inoperative without anyway, But it is recommended to set it to between 2 to 5 % of battery 20hr rate, older batteries it is on the upper end, then cross reference against SG`s to fine tune,

    Have a good one
    Tim
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  • tallgirl
    tallgirl Solar Expert Posts: 413 ✭✭
    #4
    Re: Recommendations please

    The "correct" value is the lowest value that still allows "Parameters Met" to be set by the FN-DC.

    The advantage of this approach is that it produces few to no false-positives for a bank being fully charged and it gives a better indication of aging because "Parameters Met" starts happening less and less often indicating that either an equalization cycle is in order, or else the batteries are just getting older and nothing can be done about it.

    Whatever you do, DO NOT just "set" the value and assume is going to work out.

    And good catch by Tim -- you don't list an FN-DC, but you really need to have one so you can monitor AH in and AH out to at least get an idea of cycle efficiency.
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  • offgrid
    offgrid Registered Users Posts: 20 ✭
    #5
    Re: Recommendations please

    Thanks everyone,

    FN-DC...no, I don't have one, I don't think I do. Don't know what one is to be honest. I'm guessing battery monitor. Is there a workaround or should I leave this setting at zero until i get one ? These batteries are new (about a month and a half old), I would hate to lose them before I can use them.

    blackswan555, I was getting this from the CC (flex80) in the advanced menu.

    BB, These are FLA's that are cycled daily. I have a small load that gets recharged using the 4 - 210 watt kyocera panels.

    Thanks, Tom
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  • tallgirl
    tallgirl Solar Expert Posts: 413 ✭✭
    #6
    Re: Recommendations please

    Click this link -- http://store.solar-electric.com/oupoflsymo.html -- buy that product.

    You may also need shunts. You can get them here -- http://store.solar-electric.com/mkb-500-50.html
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #7
    Re: Recommendations please
    Wondering what value to give the "absorb end amp" it is currently set at 0 (by default). If you have links to discussion that would be great too.
    Tom,

    There’s perhaps more art than science to this issue. The value depends upon battery type, charge voltage, battery age and health, and on whether there are external loads.

    Trojan Battery’s User’s Guide (diagram, page 12) implies that a FLA battery bank is full when a float current of 1% to 3% of capacity will float the batteries. Accordingly, you could try setting the Absorb End Amp value at 370 Ah x 2% = 7A and see what happens. New batteries typically require lower current, and older batteries typically require higher current.

    You’ll need a higher setting if you have loads on the bank at the same time, as the controller will need to be able to power them as well.

    A battery monitor (FN-DC, Link 10, etc.) would be a useful tool as well. However, they’re not fool-proof, and they do require initial setup and calibration. Their efficiency factor needs to be adjusted as the battery bank ages.

    FWIW, I don't use this feature in my system. It's probably useful for battery banks that are kept on standby and just need a daily "goose", but batteries that are cycled daily get by just fine by setting the absorption timer.

    You may also find this old Rolls / Surrette battery bulletin to be useful: http://www.theresourcestore.ca/pdf%20files/Surrette%20Charging%20Instructions.pdf

    Finally, don’t forget a battery temp sensor to plug into the charge controller to allow for battery temperature compensation.

    HTH,
    Jim / crewzer
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  • tallgirl
    tallgirl Solar Expert Posts: 413 ✭✭
    #8
    Re: Recommendations please
    crewzer wrote: »
    A battery monitor (FN-DC, Link 10, etc.) would be a useful tool as well. However, they’re not fool-proof, and they do require initial setup and calibration. Their efficiency factor needs to be adjusted as the battery bank ages.

    This is why my recommendation is to set the return amps to the lowest value that produces "Parameters Met". As the batteries age, the value is simply incremented. When the amount of power being wasted by the increasing return amps value gets to be too much, time for new batteries.

    No need to refer to bulletins or calculate percentages. Just lower until it breaks, increment by one, wait for that to stop working and increment by one again.

    I have a number of comments in to Outback engineering at the moment and am waiting to see if they get turned into some new firmware I can try out any time soon.
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