Backup Power for Solar Pumps
Generally solar pump customers get more water then they think (even pumping on cloudy/hazy days!) but its good to plan for days with less or no sun.
How else can you power a solar pump system?
A number of solar pumps of high voltage are designed for use with solar or 220v AC power only. Lower voltage pumps can generally be run off solar and batteries directly. Usually generators or AC power are also options with an AC to DC converter. There is also a converter (usually a DC to DC step-up for running off your trucks battery if needed.
Pumping + Charging batteries vs Pumping Only
With systems that are capable of doing so, you’ll be able to select SOLAR or BATTERY modes. In BATTERY mode the solar panels will charge the batteries, and the pump will run off battery power rather than solar power directly. The solar charge controller inside your pump controller that facilitates charging, prevents overcharging, and prevents discharging batteries to a damaging level. It should be mentioned that during charging, some power and voltage is lost, leading to a 15% to 25% decrease in pumping efficiency. These decreases are greater for deeper wells and higher heads.
What Type of Batteries should I use?
Batteries must be deep-cycle batteries, not standard car batteries. Deep-cycle batteries are designed to accommodate much lower continual discharges than regular car batteries and are usually sold as “marine” or “RV” batteries. Lead Acid Batteries are the cheapest deep-cycle batteries and are easiest to find. Most customers feel Lithium-Ion batteries are still too expensive. AGM batteries are an increasingly popular option.
How many batteries do I need?
If you are adding batteries in order to pump more water than is possible in a solar day, you will need to increase the number of solar panels in your system. Add solar panels in parallel to maintain the same voltage to the controller. More batteries can also be added for greater total storage capacity, as long as they are added in parallel at the same voltage. Batteries should be at the same voltage as the Solar Panel Array. Use 12v batteries in sets or 2 in series for 24v systems and sets of 4 for the 48v systems. More sets can be added in parallel as needed, but we recommend starting small and adding as needed. (If using 6v batteries, you’ll need double the number series!) Battery and solar panel wiring diagrams are available for RPS solar pumps as an example.