During the cold winter months, it is critical to remember how temperature affects battery health. Heat accelerates the chemical activity in a battery, while cold temperatures will slow it down. The normal lead acid battery operating temperature is 77 degrees Fahrenheit. Colder temperatures during the winter result in colder temperatures for many battery strings. The drop in overall temperature can increase battery life, decrease performance, decrease water usage, and decrease maintenance requirements. The biggest concern of those is your battery’s performance. You can drop 10% or more of the capacity of your battery for electrolyte temperatures 60 degrees Fahrenheit and 20% or more for 40 degrees Fahrenheit.

Many battery users are concerned about the electrolyte in a battery freezing. While that is a possibility, it takes extreme weather conditions to do so. A typical 1.215 specific gravity battery has a freezing point of around -32 degrees Fahrenheit, while a 1.250 gravity battery is around -61 degrees Fahrenheit.

Below are tips for minimizing the effects of cold weather on your battery systems:

  • Check your heating system in the battery room or cabinet (if available) and make sure that it is functioning properly. Lead acid batteries like to be in an environment of 77 degrees Fahrenheit which can be a challenge during the winter. For VLA batteries, check the temperature of your electrolyte to determine battery temperature, as it can be different from ambient temperature. For VRLA batteries check the temperature of the battery at the negative post.

– Lower temperatures condense the electrolyte of the battery and as a result, it concentrates the electrolyte. As such, electrolyte temperature below 77 degrees Fahrenheit will result in approximately .001 higher voltage reading per 3 degrees Fahrenheit. A typical 1.215 gravity battery at 77 degrees Fahrenheit would be 1.222 at 56 degrees Fahrenheit. Keep an eye on this during your winter month PMs. A high gravity reading may raise concerns, but in reality, this is very normal.

  • Temperature compensated charging is a great tool you can use to help alleviate some of the cold effects. Some newer chargers come equipped with Temperature Control Sensors on the batteries. This allows for the charge voltage on the batteries to be reduced or increased based on the temperature at the sensor point. Please reach out to us with the charger model and serial number if you aren’t sure if your charger has this functionality.
  • If you do not have temperature-controlled charging as a feature, you can manually adjust charger float and equalize voltage. This is much more challenging to keep up with as you won’t know the temperature daily to adjust the charger to. Most recommended float charge voltages are based on a battery sitting in an environment that is 77 degrees Fahrenheit. Consult your manufacturer’s operation manual for the recommended adjustment based on ambient temperature.

Example: A C&D VLA battery that normally operates at 77 degrees Fahrenheit might have a float voltage of 2.20 volts per cell. The corrected float voltage at 56 degrees Fahrenheit would be 2.228 volts per cell. So, a 60-cell string that normally floats at 132VDC would now be adjusted to 133.68VDC to improve cold weather performance.

Source: C&D Standby Battery Vented Cell Installation & Operating Instructions (RS-1476)