EPV is the battery end load voltage in the condition of discharge. Many kinds of standards rule EPV definitely in different discharge rates and temperatures. EPV is different according to different discharge rates: it is low when discharge in high current, contrarily, it is high when discharge in low current.
During the battery charging, a large portion of electrical energy transform to chemical energy, balance energy transform to heat energy and others. Charging battery with heat is a normal phenomenon , but if the surface temperature of the batteris is too high, it should be timely checked the battery charging current and see if it is over the standard or if the internal short-circuit happens. Amount of heat is little related to electrolyte.If the sealed lead acid battery electrolyte is lower, then the internal resistance will increase and cause warming, leading to the high battery terminal voltage while charging. Cell aging, dry electrolyte, internal short-circuit and so on may also result to battery fever. Chargers can not be in constant voltage charging while late charging time , it will cause the battery voltage exceeds the allowable values, the battery temperature will rise, even cause the battery bulging and end the battery service life.
The self-discharge, also known as charge retention capacity, that means when it is in open circuit state, the maintain ability of battery's storage electricity under certain environmental conditions .During storage time, the rate of capacity loss is called self-discharge rate.It is mainly affected by the manufacture technology, materials, storage conditions and other factors, which is an important parameter to measure the lead acid battery's performance.