Batteries @ 50% ???

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boywonder
boywonder Registered Users Posts: 16 ✭
in Solar Beginners Corner #1
I have the TriStar TS-MPPT-45. I now have a battery bank of six T-105 RE's (250ah @ 100 hrs, 225ah @ 20 hrs). They are wired in Series w/common buss for + and - sides with equal length cables from battery to buss.

My question is: How can I tell when my batteries are down to 50%?

I have read the Owners Manual and watched the 1 hour Training Video for the Controller on MorningStar Website. I'm assuming somewhere while scrolling the data on my Remote Digital Meter 2 it will give me this info. Could someone enlighten me on this. My apologies for being such a newbie and not so knowledgeable with electricity. I've downloaded some Solar Electric Terminology Glossaries so I can try to keep up with you professionals and guru's. lol

boywonder
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,457 admin
    #2
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    Re: Batteries @ 50% ???

    Welcome to the world of managing your battery banks... With a standard (good quality) solar charge controller, you cannot tell.

    Your only choices:
    • Monitor resting voltage (and temperature) of battery bank (yes, let the batteries set for ~3 hours with no load/no charging--pretty useless for most people that use their systems)
    • Flooded cell batteries, you can use a Hydrometer (and thermometer) to measure specific gravity and compare against a chart for your battery. Most accurate but still a pain to do.
    • Battery Monitor, will measure current into and out of the battery bank over time. Estimates the state of charge of the battery bank and displays on meter (AH, percent of charge, etc.). I really like to push these for people with AGM/Sealed battery banks. And they are very handy for flooded cell battery banks too--Especially for spouses, kids, and visitors that you don't want anywhere near your batteries with a volt meter or hydrometer.
    -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 ✭✭✭
    #3
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    Re: Batteries @ 50% ???

    This glossary might help you understand some of the alphabet soup of terms that gets dished up around here: http://forum.solar-electric.com/showthread.php?t=6136

    Your charge controller isn't going to do much for telling you the SOC of your batteries. It can give you a Voltage reading, but that's not very meaningful. Under charge or load conditions the V is a poor indication of charge. If the battery is resting (no current in or out for at least two hours) it can be of use.

    The best way to tell SOC with your Trojans is with a hydrometer; measure the specific gravity in each cell. You're looking for the level (as in 1.265) as well as consistency (close readings between cells). This too is best done with the batteries at rest.

    To know what state they're in 'on the fly' so to speak, you need to use a battery monitor: http://www.solar-electric.com/metersmonitors.html They require some initial programming, but after that will keep track of the current flowing in and out providing a fairly accurate SOC reading.
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