12v 100w off grid system isn't charging like it used to

flylow1970flylow1970 Registered Users Posts: 2
Thanks in advance for any help you can provide.
I have a 12v off-grid small system in my shed.  I put it together about a year ago and had to learn a lot beforehand.
Everything was working well until this summer when the system start charging slowly and I could compare to a year ago.
My system is:
Renogy 100w 12v panel
Wanderer 30a charge controller
2 35ah deep cycle batteries in parallel 'chromebattery'
I have a bayite power energy meter (with shunt) hooked up to constantly measure voltage.
I also have a micro solar inverter connected directly to the battery (off for these tests)

The battery was at 12.0v give or take .1 during these tests and under no load.
I measured the amperage and voltage from the panel directly (just connected to the multimeter) when the sun was full on, but then the clouds came so other measurements are not full sun so bear with me.

Full sun: 5a and 19v from the panel

With panel hooked to controller I measured maybe 1.5-1.8amps with meter between controller and battery (with pretty good sun)
So I then just hooked the panels directly to the battery, and measured 2amps maybe a little more.  But the sun was not full, I switch to measuring the panel and it was at maybe 3.0amp.

So with the charging providing less than 1/2 the power to the battery I thought it was the charge controller but then the direct connection to the batter was barely above 2amp.   Last summer with the same equipment I would get to 14v after a day or 2 with no or a very small load (small PC fan to circulate air).  

With the battery directly wired to the panel I watched the volts increase slowly on the battery but then adding the multimeter I get that low amp readying but maybe that's just not the way to measure (I'm a novice).  I think I measured voltage that way but I don't recall it being different that the energy meter.
As I said everything is <1 year old.
Those test were yesterday and with no load and a sunny day it's not at only 12.4v!
An ideas what this might be?  Any other tests I can run?
Can I leave it direct connected to the battery for 1hr or so and see how much they charge?  Or is that a bad idea.



  • DcmikeDcmike Registered Users Posts: 21 ✭✭
    im thinking your battery's are dead. for me a reading of 12 volts on a 12 volt battery equals dead. mine never dip below 12.6 if i can help it
  • BB.BB. Super Moderators, Administrators Posts: 29,976 admin
    Clean panel pointing at sun and no shade on panel (within 10 degrees is ideal) should give you near Imp when directly connected to battery (and battery voltage is under 15.0 volts while charging). Meyer set to10 amps full scale).

    If you see 80% or more of Imp, panel and wiring is proble probably good. If you see 50% or less, then you probably havea wiring, connection, or panel problem.

    If you can, connect panel directly to battery (make sure polarity is correct. If backwards, you will ruin the panel almost instantly). Measure voltage at battery (say 13 volts). Measure voltage at panel (if you can open the junction box of the panel, that is ideal). If panel voltage is (for example) 14 volts or less, wiring is good. If voltage is over16 volts or so (over 2 volts drop), them you havea wiring problem).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Solar Expert Posts: 3,245 ✭✭✭✭✭
    Put a load on the battery while looking at the voltage, if the voltage collapses the battery has little to no capacity, as such will accept little to no current from the panels, assuming all wiring is in good order.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • BB.BB. Super Moderators, Administrators Posts: 29,976 admin
    There are probably multiple issues here... Even if your battery has failed (under charging?), you should still be able to run some basic tests and see how your system is performing (solar panel, wiring, charge controller, etc.)... As long as your battery is over ~9 VDC (most charge controllers need a "good battery" voltage to boot up).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • flylow1970flylow1970 Registered Users Posts: 2
    Thanks for all the suggestions.  I think the wiring is OK since it's all very close together I can see it all.  But I'll check that along with the other suggestions this weekend.  Appreciate the help.
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