What batteries are used in the Tilt Hydrometer? The Tilt Hydrometer comes with a pre-installed battery that lasts 12-24 months depending on usage. When the batteries need changing they can be replaced with a CR123A battery as pictured below. Other brands will also suffice. Related articles Hydrometer Specifications TILT Hydrometer - How do I get the TILT Hydrometer to work with Wi-Fi the same way as the GF30? GCAST Connection Issues What is BU/GU? How to empty glycol from the GC4 Glycol Chiller