Clarification on battery charging

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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #32
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    Re: Clarification on battery charging

    To me, 14.4 v would be just on the beginning of the gassing voltage. I am not sure that you could raise a very large bank from 13.2 V to 14.4 in 15 Minutes. Of course it's a 12 v charger made for a RV with a couple batteries. I guess the point I was trying to make is that these have a algorithm that can do some weird things. Once you interrupt them, they will not reset to another full charging cycle until they drop down the the " Discharged Battery " threshold. Whoever programed the logic into them, must of had something different in mind then I usually do. This one does not have a Absorb cycle, so it's a moot point.

    I actually found this charger for $159 with a little searching, not bad for a 60 amp charger. Keep in mind that 60amp's @ 12 V is just at the point that a 15 Amp breaker will hold with out tripping. This charger is meant to be hard wired, but you can add a power cord. Also keep in mind that it may or may not pass the ability to hold the Max output of 60 Amps for a couple hrs on a 1,000 AmpHR's on a depleted bank, thats my personal test in 90+ degree weather. If it keep cutting it's self back to cool down it just wastes a bunch of gas and can double or triple your charging time.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #33
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    Re: Clarification on battery charging
    Cariboocoot wrote: »
    Float = no bubbling. No bubbling = no mixing. No mixing = stratification.
    So it is possible.

    Yes, and it is possible that a jar of salt water will separate into high and low salt strata, or a jar of warm water could separate into hot and cold strata. But it is far less likely to happen if no charging or discharging is taking place to create stratification in the first place.
    If I mix a container of 1.25 SG sulphuric acid, without putting it into a battery, and let it sit on a shelf will it stratify???


    More:
    A fairly authoritative reference (mentioned here: http://forum.solar-electric.com/showthread.php?17994-When-does-electrolyte-stratification-occur) indicates that the stratification does not arise spontaneously but rather results from the creation of higher density "pockets" of sulphuric acid within the surfaces of the plates. That higher concentration solution then manages to sink toward the bottom, sliding along the surface of the plate, without mixing much with the rest of the more dilute acid between the plates.
    Stratification results from charging, and so a battery which is in float may not get destratified, but it will not stratify in the first place if it was fully mixed by the time the Float stage started.
    SMA SB 3000, old BP panels.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #34
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    Re: Clarification on battery charging
    inetdog wrote: »
    A fairly authoritative reference (mentioned here: http://forum.solar-electric.com/showthread.php?17994-When-does-electrolyte-stratification-occur) indicates that the stratification does not arise spontaneously but rather results from the creation of higher density "pockets" of sulphuric acid within the surfaces of the plates. That higher concentration solution then manages to sink toward the bottom, sliding along the surface of the plate, without mixing much with the rest of the more dilute acid between the plates.

    During discharge, does the creation of lower density "pockets" of water occur at the surfaces of the plates? Could that lower concentration solution rise toward the top, sliding along the surface of the plate, without mixing much with the rest of the more concentrated acid between the plates?

    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 ✭✭✭
    #35
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    Re: Clarification on battery charging
    inetdog wrote: »
    If I mix a container of 1.25 SG sulphuric acid, without putting it into a battery, and let it sit on a shelf will it stratify???

    Yep.
    How long it will take is another issue.
    In general the small batteries don't suffer noticeable stratification under any circumstances, even as they sulphate from being left discharged for long periods. There simply isn't enough physical room for the slight gradations in acid concentration to become noticeable.

    The taller the vessel, the less activity within, the greater the stratification potential.

    AGM's, of course, have about zero potential for stratification because they aren't big vats of electrolyte solution.

    Mostly this falls under the same category as worrying about 0.001 differences in SG or 0.01 Volts or 1 mA et cetera. Technically the condition may exist, but how much does it really affect system performance? Not enough to bother with in most cases. Worry about temperature and the quality of the wiring first.

    But yes, deep cycle batteries do benefit from being dishcarged and recharged occasionally, so continually floating them is not ideal.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #36
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    Re: Clarification on battery charging
    Cariboocoot wrote: »

    AGM's, of course, have about zero potential for stratification because they aren't big vats of electrolyte solution.

    I have actually seen some references to stratification within AGM batteries, but unlike flooded batteries it occurs as a gradient from one part of the separator to another if the current flow is not uniform over the whole mat surface and has little or nothing to do with gravity. But in an AGM it definitely will not happen when the battery is just sitting idle.
    SMA SB 3000, old BP panels.
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