The influence of temperature on VRLA batteries

K=0.006/℃, K=0.008/℃ for 3-hour rate capacity experiment, K=0.01/℃ for 1-hour rate capacity experiment. It can be seen from equation (1) that when the ambient temperature is higher than 25°C, the actual discharge capacity Ct of the VRLA battery is greater than the design rated capacity Ce; while when the ambient temperature is lower than 25°C, its actual releasable The capacity Ct is lower than the design rated capacity Ce. It can also be seen from the value of the temperature coefficient K that the greater the discharge rate, the greater the effect of temperature on capacity.

The battery capacity decreases with decreasing temperature, which is closely related to the serious influence of temperature on electrolyte viscosity and internal resistance. When the electrolyte temperature is high, the diffusion speed increases, the internal resistance decreases, and the electromotive force also increases slightly. Therefore, the capacity and active material utilization rate of VRLA batteries increase with temperature. When the temperature of the electrolyte decreases, its viscosity increases, the ion movement is subjected to greater resistance, and its diffusion capacity decreases. At low temperatures, the resistance of the electrolyte increases and the resistance of the electrochemical reaction increases, resulting in a decrease in battery capacity.

Under low-temperature working conditions, the spongy lead on the negative plate can easily become small-sized crystal grains, which can easily freeze and block the small holes, thereby greatly reducing the utilization rate of the active material. If the high-current discharge is used under low temperature and severe conditions, the pores in the negative electrode active material will be more seriously blocked, and the spongy lead may become dense PbSO4, which greatly reduces the amount of electricity that the battery can discharge. For the positive plate, its temperature coefficient is negative, so it has a higher electrode potential at low temperatures. Thus, at low temperatures, the positive electrode discharge rate is much greater than the negative electrode discharge rate. In this way, before the negative electrode generates the PbSO4 layer, the process of converting the positive electrode PbO2 to PbSO4 has ended, so the positive electrode plate does not generate dense PbSO4 grains at low temperatures. Therefore, too low temperature will lead to a decrease in the capacity of VRLA batteries.