Start with half box of baking soda dissolved in a couple gallons of water. Pour this slowly over the batteries. After all the foaming, rinse with clean water. Do not spray, causing splatter, flood the battery without pressure until they are rinsed. Rinse and wipe any possible baking soda solution off the body. Do not do this over a clean place on your driveway, it needs to be rinsed quickly to prevent staining concrete.
Then follow advice above and clean and wire brush all battery terminals and if cable lugs are severely corroded or eaten away, replace all cables. Really bad acid contamination can eat right up into the cables at the lug making for a poor connection.
That is my way
