New 100 watt System Battery/Charge Issue

S_Andrews
S_Andrews Registered Users Posts: 3

Hello All

I recently installed a small 100watt system and I'm having a few issues with charging. The only device connected to the system appears to be draining the battery far too quick. Also, yesterday my charge controller was indicating a battery over-discharge. Here are the specs of the equipment -


  1. 100 watt mono panel

    Voc – 21.6

    Vmp – 17.9

    Imp – 5.72

  2. Charge Controller

    Wanderer 30A PWM

  3. Battery (27DC-6)

    Marine Type

    CA 720

    AH@1A – 115


The device that I am running has a power requirement of 4.6A @ 13VDC.

I made sure the battery was fully charged and connected the device. The next day (early morning) the battery was down to 4.5 volts. I disconnected the device and allowed the solar panel to charge the battery all day. I reconnected the device that night (battery @ 13.7 volts) the next morning it was drained down to 4.5 volts again. I disconnected the device and allowed the battery to charge. After several hours the controller then displayed an over-discharge condition. I disconnected everything and reconnected to perform a “reset” and it began to charge again.

I would have thought that with this size battery and charger that it would not have been a problem to power a device requiring 4.6amps continuously. My thoughts were that during the day the solar panel would be large enough to maintain the battery voltage of 13vdc while allowing the device to run. Then at night the battery would have enough stored power to run the device until sunrise. Maybe I'm missing something. I'm beginning to think the battery may be faulty. Any help would be greatly appreciated.

Also, The panel is mounted correctly (at the correct angle) and exposed to direct sun for approximately 11 hours. I'm showing almost 20vdc on the solar side of charger.

Thanks

Comments

  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,037 ✭✭✭✭✭
    You're running a device 24/7 that requires 4.6 amps. At best you will get 5 hours of the equivalent of full sun.  Do you see a problem? It's called deficit charging. You will need 3 more panels and at least another battery to be able to make enough power to keep up with your needs

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • S_Andrews
    S_Andrews Registered Users Posts: 3
    edited August 2019 #3
    You're running a device 24/7 that requires 4.6 amps. At best you will get 5 hours of the equivalent of full sun.  Do you see a problem? It's called deficit charging. You will need 3 more panels and at least another battery to be able to make enough power to keep up with your needs

    I appreciate the reply. Wow, that's quite a large investment for what I'm trying to accomplish. Unfortunately my budget won't allow me to build that system all at once. I'm fairly new to solar power so forgive my lack of knowledge. Based on an online calculator I came up with 25 hours of run-time @ 4.6 amps with a fully charged battery rated at 115ah. I realize calculations vs real world vary significantly in some instants. But with a fully charged battery at sunset I would have expected the unit to still be running by the next morning. I haven't timed it but I'm guessing I'm only getting 3-4 hours of run time before it shuts down.

    I have a meter that will data-log I'm installing to get a better picture of the charge rate throughout the day.
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,037 ✭✭✭✭✭
    edited August 2019 #4
    A single panel will struggle to power your load alone for all but a couple peak hours of the day. After that you're drawing battery power and not charging at all. For battery longevity you should not discharge more than 25% of the capacity a day. 50% is going to severely shorten the batteries life and 100% will ruin the battery in very short order.
     Your battery isn't a true deep cycle battery, its a sort of hybrid. Hint, any battery with cranking amps in the description isn't a real deep cycle.. This is another strike against having a reliable system. You should look into some GC-2 type Golf Cart batteries. They are designed to be cycled.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • 706jim
    706jim Solar Expert Posts: 514 ✭✭✭✭
    Is this "device" a refrigerator?
    Island cottage solar system with 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 30th year.
  • S_Andrews
    S_Andrews Registered Users Posts: 3
    706jim said:
    Is this "device" a refrigerator?

    No, it a small dehumidifier (non compressor type).
  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    4.6 x 13v = ~60w x 24hrs = ~1,440 watt-hours/day.  A 100w panel, completely unshaded and properly tilted, might produce about 3-400 watt-hours/day on sunny days in most locations.

    The battery capacity (in new condition) might be ~100ah (1,200 wh) at that rate of discharge (~20hr rate vs ~100hr rate spec'd), and with  C.A. spec will not be designed for deep cycling.  Assuming 16hrs load with little/no solar, the load would be taking the battery down 7-800wh to a ~30% state of charge.  At 4.5v, it's essentially dead (0% SOC), and may not be recoverable to full capacity.  That it's dead in the morning suggests it wasn't really fully charged the day prior ,and/or has already lost significant capacity.

    3-400wh/day would just about cover the 60w load for the 8hrs there's some solar power (with a bit of extra current for charging mid-day, but maybe not enough to fully cover load in the early/late hours with weaker sun and bad angles).

    As others have noted, more panels (or an alternate charge source) will be needed to power the load as described. 

    I'd also suggest setting the charge controller low-voltage disconnect to ~12v if possible (assuming the load is powered via the controller), or adding a LVD relay for the load circuit if not.  The controller likely shuts itself down at ~10.5v to protect itself, but at that voltage the battery is nearly dead.  12v would be a bit under 50%, and better protects the battery from permanent damage.  The load itself may stop at some low voltage, but also to protect itself (not the battery).  
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    Don't feel bad, almost everyone has overestimated their system in the beginning, though not all will admit doing so, the best thing to do right now is disconnect the load and allow the battery to fully charge to 14.4V then start from the beginning with the load and how long it's required to operate. This will establish the battery capacity required, then the charging requirements can be determined to satisfy the needs of both the load and the battery, it's really the only way to achieve success.


    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • mountainman
    mountainman Registered Users Posts: 439 ✭✭
    My question is?, Did the numbers come from a label on the dehumidifier? The best money I've spent in my solar system is, 
     a watts up dc watt meter. I couldn't find one on NAWS. But Ebay has them. Around $15.
    This will tell you what your loads are. 
    2kw array 6 345 q cells  make sky blue 60 cc
     6 230ah GC @36 volts 
    18 amp accusense charger. 3650 champion 
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    SO I take  it you are plugging this directly into the 12 volt battery bank and not using an inverter and wall wart...

    Thermoelectric Peltier devices, do tend to run lower max wattage at the expense of running continuously. If run during the day, I would be surprised if the battery was ever fully charged. Solar panels are rated at Standard test Conditions, but produce closer to Normal Operating Cell Temperature values (NOCT) which run about 75% of the STC so the solar panels is producing about 75-80 watts during the day. In addition to this flooded lead acid batteries, even if we assume the 'marine' battery is a true deep cycle  (which is rare), require about 15-20% higher voltage than the battery would be at rest to allow the current to flow into the battery. You basically lose 15-20% of the incoming wattage to this for charging.

    As others have mentioned with a fixed array/panel the max you can expect to get is roughly 6.5 hours of direct sun light equivalent (3-4 hours is low I'd say for most areas this time of year, but understand that this is for sunny days, even 'partly cloudy' will reduce this considerably! 

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.