Entrance Gate set up

Any concerns using the following panel with an inexpensive PWM 20 amp controller?   The service is a 12 volt DC motor driving a hydraulic system to open and close an entrance gate a few time a day.  Any recommendations for the best battery to use?  Replacing the entire panel/battery system.

20 watts monocrystalline, 17.5 Vmp, 1.14 Imp

http://www.ebay.com/itm/New-20W-Solar-Panel-12V-20-Watt-Mono-for-Off-Grid-RV-Boat-Battery-Charge-Camping-/161884201303?hash=item25b10ce157:g:c9EAAOSwiwVWR2zw .

PWM CC is one of the cheap Chinese nominal 12 volt PWM controllers.




3850 watts - 14 - 275SW SolarWorld Panels, 4000 TL-US SMA Sunny Boy Grid tied inverter.  2760 Watts - 8 - 345XL Solar World Panels, 3000 TL-US SMA Sunny Boy GT inverter.   3000 watts SMA/SPS power.  PV "switchable" to MidNite Classic 250ks based charging of Golf cart + spare battery array of 8 - 155 AH 12V Trojans with an  APC SMT3000 - 48 volt DC=>120 Volt AC inverter for emergency off-grid.   Also, "PriUPS" backup generator with APC SURT6000/SURT003  => 192 volt DC/240 volt split phase AC inverter.  

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,639 admin
    At 5% to 10% rate of charge, the typical 12 volt deep cycle battery would be:
    • 1.14 Amps / 0.05 = 23 Amp*Hour maximum
    • 1.14 Amps / 0.10 = 11 Amp*Hour minimum
    If you go with Sealed (AGM, GEL), then you can probably be fine with the ~23 AH battery (or a bit larger). AGM/GEL have lower self discharge and tend to be more efficient charging.

    Deep Cycle flooded cell will require you to check water level every 1-2 months typically.

    Does your charger have an AGM/Sealed battery charging option (typically 14.4 volts max for AGM, and 14.2 volts max for GEL).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MarkCMarkC Solar Expert Posts: 212 ✭✭✭
    It's my Son's gate.  He decided a while back to "buy" a warranty and replace the auto style battery that he bought, if it goes bad.  I've told him that he should eventually go with a ~ 30 AH AGM (I have several from my UPS dealings).  Seems we are in agreement.  I'm not sure about a specific AGM setting, but I believe I can modify the float voltage.  I'll check.

    The "idle" current is less than 10 ma, but I do wonder if the charging losses are significant with only a 20 watt panel.
    3850 watts - 14 - 275SW SolarWorld Panels, 4000 TL-US SMA Sunny Boy Grid tied inverter.  2760 Watts - 8 - 345XL Solar World Panels, 3000 TL-US SMA Sunny Boy GT inverter.   3000 watts SMA/SPS power.  PV "switchable" to MidNite Classic 250ks based charging of Golf cart + spare battery array of 8 - 155 AH 12V Trojans with an  APC SMT3000 - 48 volt DC=>120 Volt AC inverter for emergency off-grid.   Also, "PriUPS" backup generator with APC SURT6000/SURT003  => 192 volt DC/240 volt split phase AC inverter.  
  • BB.BB. Super Moderators, Administrators Posts: 32,639 admin
    Roughly:
    • 0.010 amps * 12 volts * 24 hours per day = 2.88 Watt*Hours per day
    That is pretty small vs the 20 watt panel's charging capability:
    • 20 Watts * 0.61 DC system derating * 4.0 hours of sun (average ~9 months a year) = 42 Watt*Hours per day (rough typical charging non-winter time)
    I would not worry very much unless the gate is used dozens of times a day (do you know the amp draw when operating--i.e., 4 amps * 30 seconds open/close cycle * 5 times a day). "Made up daily usage" example:
    • 4 amps * 12 volts * 30 seconds * 1/3,600 seconds per hour * 5 times a day = 2 Watt*Hours per day
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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