If your tester displays a “Low Voltage” error, it means the battery voltage has dropped below the level required for the tester to perform an accurate reading. Most standard testers need at least 9. 6 volts to function correctly, and anything below this can prevent the test from. . My MPPT 75/15 does not charge battery, showing the solar voltage always about 0. 5 V below battery voltage. This is independent of sun exposure. Wiring has been double checked. I would appreciate any suggestions. The PV voltage will raise to battery voltage when theres not. . Voltage thresholds indicate battery health: a 12V lead-acid battery below 11. 8V (under load) or 12. 4V (resting) signals severe discharge or sulfation. Lithium-ion (LiFePO4) cells dropping under 3. 2V/cell risk capacity loss. Pro Tip: Voltage alone isn't. . Their real voltage, and therefore charge status, is best understood as a range that varies between the different battery types. Whether Lithium Iron Phosphate (LFP or LiFePo) batteries, AGM, or Flooded Lead Acid, the battery's internal chemistry will determine the voltage status range between full. . Battery voltage is a fundamental electrical measure indicating the electric potential difference between two points of a battery. This. . power required to keep the batteries at the proper float voltage. When AC power fails, the batteries will di charge in order to provide the necessary backup power to the load. It is the responsibility of the customer to make sure t e batteries are not discharged below manufactures recommendations.