1. Deep Discharge

The depth of discharge has a great influence on the cycle life of the battery. If the battery is often discharged with a high current or is often under voltage, and it cannot be recharged in time, then the sulfate particles it produces will be large, and the active material on the plate will not be fully utilized. Thus, if the battery is deeply discharged frequently, the actual capacity of the battery will gradually decrease and the cycle life will be shortened.

2. Discharge Rate

It is generally stipulated that the capacity of the 20-hour discharge rate is the rated capacity of the battery. If you use a discharge rate lower than the specified hour, you can get a battery capacity higher than the rated value; if you use a discharge rate higher than the specified hour, the discharged capacity is lower than the rated capacity of the battery, and the discharge rate also affects the battery terminal Voltage value.

When the battery is discharged, the electrochemical reaction current is preferentially distributed on the surface closest to the main solution, resulting in the formation of lead sulfate on the electrode surface which blocks the inside of the porous electrode.
The above-mentioned problems become more obvious during high-current discharge. Therefore, the larger the discharge current, the smaller the capacity of the battery and the faster the terminal voltage value declines, that is, the end-of-discharge voltage value decreases with the increase of the discharge current.
 

3. Temperature

The rated capacity of the battery is referred to as the value of the battery at 25℃. It is generally considered that the ideal working temperature of the valve-regulated sealed lead acid car battery is 20~30℃.

When the battery temperature is too low, the capacity of the battery will decrease, because the electrolyte cannot fully react with the active material of the electrode plate under low temperature conditions. Such a decrease will not be able to meet the expected backup use time and remain within the specified depth of discharge, which will easily cause over-discharge of the battery.

Judging from the external parameters of the battery, the voltage has a great relationship with the temperature. When the temperature rises by 1℃, the voltage of a single cell drops by 3mV. In other words, the voltage of a lead-acid battery has a negative temperature coefficient, and its value is -3mV/°C. 

In the same way, the rising ambient temperature will easily cause over-discharge of the battery, and high temperature will also cause the battery to lose water and thermal runaway. Temperature is a major factor affecting the normal operation of the battery. In solar photovoltaic systems, the controller is generally required to have a temperature compensation function.