Depends on usage and chemistry. Only flooded lead-acid types need distilled water. There are special battery fluids as well that contain cadmium sulfate which is better than just distilled water. batteries should be checked monthly for dirty/loose connections dirt on top of casing fluid levels etc dirt should be rinsed off with water and a paintbrush. The brush is to loosen the dirt. any corrosion build-up should be removed by brushing with an old toothbrush and a paste of bicarbonate soda and water rinse well with water corrosion is often caused by loose connections after cleaning smear the terminals lightly with grease or petroleum jelly and re-tighten till firm any loose connections are tightened. The fluid level should be to the bottom of the dip tube the caps fit into so that the plates are covered with electrolyte if not add battery fluid or distilled water don’t add acid.