After having sold and installed some solar water pumping systems, the batteries will be expensive and unnecessary. It's easier to oversize the solar array to have some water production on cloudier days.
Play it by ear and expand as necessary if you don't have enough water. Also, pay attention to the necessary PV voltage to work the pump. You don't want to have to buy 4-10 more paneles to meet the voltage requirments.
Drip irrigation is a very simple setup for solar water pumping. Just connect the drip hoses directly to the pump and let the pump irrigate everyday. No tanks are necessary. I recommend a Lorentz brand pump which should be sold in Cambodia. They're higher quality and more expensive, but they save money in smaller diameter drip hoses, solar panel wattage, and overall expenses. Parts are available and necessary accesories are also included for long lasting installations.
