The Luster Leaf Rapitest Mini Moisture Tester 1810 does not require batteries. The product should be inserted into the soil next to the plant (not too closely) and it works off of the moisture in the soil. It will read the moisutre level and once the needle is stable, that will be the reading of the moisture level. Do not leave product in the soil. It should be used as needed only and promptly removed. You will know when the product is no longer effective when the needle no longer has movement.