If the float voltage is set to 2.30V/cell at 25°C (77°F), the voltage should read 2.27V/cell at 35°C (95°F). Going colder, the voltage should be 2.33V/cell at 15°C (59°F). These 10°C adjustments represent 30mV change. Table 3 indicates the optimal peak voltage at various temperatures when charging lead acid batteries.
There are several reasons why a lead acid car battery may overheat during charging. One common reason is overcharging, which can cause the battery to generate excess heat. Another reason is a faulty charging system, which can cause the battery to receive too much or too little charge.
A lead acid battery charges at a constant current to a set voltage that is typically 2.40V/cell at ambient temperature. This voltage is governed by temperature and is set higher when cold and lower when warm. Figure 2 illustrates the recommended settings for most lead acid batteries.
Lead-acid batteries: A lead-acid battery should come with a smart charger that allows for voltage changes when sensing fluctuating temperature ranges. It should set the voltage higher when the battery is charged at lower temperatures and a lower voltage when charging at higher temperatures.
Charging at cold and hot temperatures requires adjustment of voltage limit. Freezing a lead acid battery leads to permanent damage. Always keep the batteries fully charged because in the discharged state the electrolyte becomes more water-like and freezes earlier than when fully charged.
Nowadays modern plastics are impervious to acid so there is no risk of this happening. Myth: It is okay to store lead acid batteries anywhere inside or outside. Fact: It is good to store lead acid batteries in cool places because the self-discharge is lower but be careful not to freeze the battery.