This blog covers lead acid battery charging at low temperatures. A later blog will deal with lithium batteries. Charging lead acid batteries in cold (and indeed hot) weather needs special consideration, primarily due to the fact a higher charge voltage is required at low temperatures and a lower voltage at high 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.
Heat is the worst enemy of batteries, including lead acid. Adding temperature compensation on a lead acid charger to adjust for temperature variations is said to prolong battery life by up to 15 percent. The recommended compensation is a 3mV drop per cell for every degree Celsius rise in temperature.
Without getting into the complexities, suffice to say maintain the battery in a fully charged state, as at low states of charge the electrolyte is more water like and freezes earlier than in a fully charged state. Lead acid batteries come in a variety of types:
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.
Figure 5 : Chemical Action During Charging As a lead-acid battery charge nears completion, hydrogen (H 2) gas is liberated at the negative plate, and oxygen (O 2) gas is liberated at the positive plate.