Operation of aircraft batteries beyond their ambient temperature or charging voltage limits can result in excessive cell temperatures leading to electrolyte boiling, rapid deterioration of the cell, and battery failure. The relationship between maximum charging voltage and the number of cells in the battery is also significant. This determines (for a give ambient temperature and state of charge) the rate at which energy is absorbed as heat within the battery. For lead-acid batteries, the voltage per cell must not exceed 2.35 volt. In the case of 1.4 and 1.5 volts per cell are generally used. in all cases, follow the recommendations of the battery manufacturer.