The TM 2025 is intended to help maintain battery systems for nominal 12V to 48V systems, such as ones found in RV's or off grid homes which are regularly charged and discharged and use deep cycle batteries. The amps or watts display measures the rate of energy going in or out of your batteries so you can check your charging systems, and also to see how much energy each of your appliances use to help you conserve energy. The % Full display will help you keep track of how charged or discharged your batteries are. The volts display will let you discover if your charger systems are charging to the proper voltage, neither too high or too low, which is important for maximizing your battery life also when battery voltage gets too low you will know your battery is getting really close to being discharged. The days since charged display shows how recently the main battery (system) was fully charged, so if it hasn't been charged recently you can perform extra charging if necessary to help maintain the capacity of your batteries. The TM-2025 also can measure voltage only of a second battery set, such as the motor starting battery, or solar voltage input to an MPPT charge controller.