Entrance Gate set up

MarkC

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.

BB.

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

MarkC

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.

BB.

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