How can I tell if my system is working

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barny
barny Registered Users Posts: 8 ✭✭
in General Solar Power Topics #1
Hi, I wired up a 12v DC circuit in a barn using 2 12v truck batteries connected in parallel.  I just added a 190 watt solar panel with a 30 Amp. Enerwatt charge controller (used). It has 6 indicator lights on the left, and an LCD screen measuring amps and volts on the right.  The screen displays 12.6 volts and 0 amps, and the top light, to my understanding, (could be wrong) should be lit at all times (the others display state of battery charge).  I can use the multimeter to check the panel (and will do) and know how to check the charge controller using same.  I am wondering if the batteries are sufficiently charged and if that is why it doesn't seem to be working.  My friend had a system that charged his batteries up to 14 Volts.  The multimeter rates the batteries at 12.7 Volts. Thank you in advance.

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #2
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    You first need to understand what the Flooded Cell Lead Acid batteries "need" to be happy.

    More or less, a resting battery (room temperature) will read somewhere between ~12.0 to 12.7 (or 12.8) volts (50% to 100% state of charge).

    Floating (aka trickle charging) is something between 13.4 and 13.8 volts or so... This is not to recharge the battery, but hold it at full charge (and support other DC loads).

    Bulk charging (current regulated) is just the charge controller dumping as much current as it can into the battery bank (typically ~5% to 13% rate of charge for solar) until the "absorb set point" is reached.

    And charging (absorb charge--voltage regulated), typically 13.8 to 14.8 volts... And if you want to "quickly" recharge the battery, 14.5 to 14.8 volts. And hold that voltage to for roughly 2 to 6 hours (2 hours or less, if the battery is not deeply discharged, 4-6 hours for deeply cycled batteries). Once the battery is "fully charged", then drop back to float, or turn off the charger (or the sun sets).

    Now, a charge controller may be simple (tries to hold 14.5 volts when the sun up). Or it may be more advanced. For example, it may not do an absorb charge until the battery falls below 12.5 volts--At that point, the controller assumes the battery has been discharged and needs to be recharged.

    So--Now to your question--You have to figure out how discharged the battery is, and what the charge controller will do.

    You can estimate state of charge by measuring battery voltage... Or you can get a nice hydrometer (gold standard). And, another handy tool (aka "toy") is a DC current clamp (DMM) meter like this one.

    So, is the battery not getting charged because it is full (charge controller decision), or not charging because of wiring issues, or other problem.

    You can check the output of the charge controller (voltage same as battery voltage?). And you check the solar panel input (if ~20+ volts, charge controller not letting current through. If ~Vbatt+ 1 volt or so, generally letting current through to battery).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • barny
    barny Registered Users Posts: 8 ✭✭
    #3
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    Thanks, Bill, very helpful.  The battery reads 12.7 V on multimeter (12.6 on LCD on controller) so likely the controller recognizes that the batteries are charged and is shut off.  It the same screen registers 0 A, what does this mean?  Also, if the top red LED light is not on (Enerwatt 30 A), does this mean something is screwed up? There has been no sun, and the system runs 4, 4.5 watt LED DC bulbs.  Also, to test the charge controller, what should I set the multimeter at (I'm thinking 10 A.) I am just learning this stuff, so I am sorry for being dense.  Thank you again

    Barney
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