How To Connect a Sprinkler Controller to A Solar Panel

Solar Panel Mounted On Vinyl Fence - For Powering a Sprinkler Controller


In this article we'll show you how to hook up a remote battery powered sprinkler timer/controller to a solar panel. For the purpose of this article we're using a Vegetronix VegeSprinkler latching valve controller. There are some huge benefits to continually powering your Vegetronix VegeSprinkler:

  • You can access it any time with your phone over your local wifi network.
  • It can act as a data server, and receive sensor data from other hubs on your network, and then make watering decisions based on the sensor data.
  • You never need to change batteries.

You can run a the sprinkler controller with only a solar panel and no battery - but then of course it will only run when the sun is out.

Power Considerations

The Vegesprinkler only draws 38mA when it's awake so you should size the battery and the solar panel appropriately. At 28mA's it will draw about 1000mA-hours (I've rounded up from 912) per day. There may be days when the panels do get much light and so we will want to source batteries that will store at least 3 times that amount of energy. So It would be wise to use at least a 3000mA hour battery, so that the battery doesn't run out during cloudy periods.

We need to size the solar panel to achieve an average of 1A-Hours per day of energy. We'll be overly cautious and assume that the panel gets on average gets 4 hours at full capacity. Since it's a 12V system that means the panel must generate 12Watt-hours/day. Spread 12Watt-hours over 4 hours and that means the panel must be at least 3 Watts outout. Real world systems with battery chargers are only about 70% efficient, so we should upgrade that number to about 3 Watts/.7= 4.3Watts rounded up to 5W.

To summarize we need a 5 Watt solar panel and a 3000mA battery. I rounded up these up to make sourcing the items easier, and used a 10 Watt solar panel and a 10Ah LiFePo battery for my sprinkler system, though acknowledge that this was extreme overkill.

Battery Considerations

Batteries are greatly affected by temperature. The best types of batteries for cold environments are lithium. A rechargeable sealed lithium battery is recommended for this application. LiFePo batteries in this range cost around $20 to $30 dollars.

Safety Considerations

You definitely want to put a fuse on the battery output, so that if there is a short, it doesn't melt down or explode. I used an in-line automotive fuse that I found on amazon.

Mounting Considerations

I mounted the solar panel, battery holder, and VegeSprinkler hub on the top of a white vinyl fence. For each of these items I designed and 3D printed mounting brackets that would allow me to just slide them on to the top of the fence, without having to put holes in the fence. The parts were printed using white PETG filament. I also created an enclosure for the battery. The sprinkler was in the shade from a nearby tree, and so I had to place the solar panel about 30 feet away, and ran a cable along the top of the fence to the battery and sprinkler controller.

Wire Polarity

The cable out of the solar panel's battery charger was black for both wires and then had a battery cable connector. Because the cable wasn't colored, the polarity wasn't readily apparent. The first time I hooked up the battery I got the polarity wrong. So I had to use a battery gender changer connector to fix it.

VegeHub Considerations

The first time I hooked up the system I didn't have a way of disconnecting the hub from the power, and so if I wanted to power cycle the hub, I had to open it up, which was a pain. I subsequently added a water proof inline connector on the power input of the hub, so that I could easily power cycle it.

Part List



Battery Box and VegeSprinkler - Solar Panel is Mounted 30 ft Away on Fence


Inside the Battery Box


Other Approaches

As an end note, I have a customer that found the following integrated panel and battery that looks like a perfect match: https://www.batteryeliminatorkits.com/product-p/spr-d4w-9vdc-9kmah-ip66.htm

VG-METER-200