A good way of cleaning battery terminals is to use some baking soda and water to make a paste to easily and cheaply clean the battery terminals.
To clean the battery terminals with baking soda and water mix two tablespoons of baking soda with an equal amount of water.
Then use a toothbrush or other brush to apply the baking soda and water paste to the battery terminals and scrub it until it's cleaned.
The baking soda and water will begin to sizzle and react to the battery terminal corrosion and allow the battery corrosion to come off easily.
Then you can hose down the battery terminals to wash the corrosion away.
You can also mix some vinegar with some baking soda in a cup and pour it onto the battery terminals and that too will help remove the battery corrosion.
Or you can just use the baking soda and water in a cup and pour it onto the batter terminals to remove the corrosion.