Q: Should I use batteries in my pumping system or go solar direct?
A: DON'T USE BATTERIES! The only reason I would ever consider using batteries in a solar pumping system is if you have a very low volume producing water source (well/spring) and you need to pump as much water out of it as you can each day. Otherwise, there are several reasons to avoid batteries in a pumping system:
Using batteries in a solar pumping system lowers the efficiency as compared to going solar direct since it usually lowers the operating voltage of the pump which lowers the operating speed and flow rate of the pump.
Adding batteries to a pumping system costs more money for the batteries themselves plus a required charge controller, battery enclosure and additional disconnects and wiring.
Batteries require care and maintenance that isn't always possible in a remote location.
Batteries performance level and expected lifetime are closely connected with the temperatures that they are subjected to. If batteries are undercharged and subjected to freezing temperatures they could be damaged. If batteries are overcharged and subjected to high temperatures their lifetime will be shortened dramatically. Care must be taken to shield batteries in a remote location from temperature extremes.
You're better off all the way around if you simply go with a solar pumping system that is designed to give you all the water you need during the daylight hours without having to resort to using batteries. Store water in a tank instead of energy in a battery! For a livestock watering system or gravity fed domestic application, we recommend that you use a storage tank that can hold a minimum of 3 days worth of water.