Cold Batteries – What Happens
The cold weather is coming and one of our most common questions is how do I winterize our battery systems? To best answer this question, you need to understand how changing temperatures affect your battery systems.
High temperatures shorten the lifespan of batteries, but what happens in colder weather? The answer is relatively simple, the capacity is not available. In high temperatures, the chemical reaction which generates the power is accelerated. In colder temperatures, the same chemical reaction is slowed, reducing the amount of available power.
Cold Batteries – Performance
Let’s consider an example. Battery manufacturers state the battery capacity at 77°F (25 °C). As the ambient temperature of the battery increase, you will see an increase of total available capacity. At 100 °F, you will have 10-15% additional capacity, but it will shorten the overall life of the battery. As the temperature of the battery nears freezing (32 °F), the capacity for the same battery can drop by up to 20% with no effect to the lifespan of the battery.
So, for a 100 AHr battery operating at normal room temperature, you would expect 100 AHr of capacity during discharge. If the temperature was to increase to 100 °F, you would expect 110-120 AHr of energy. However, if you were to expose the same battery to colder temperatures, your capacity would decline to as low as 50 AHr. Without proper sizing, this would put your critical loads at risk. A cold battery is not able to provide enough energy to carry the load in case of emergency.
Source: http://www.solar365.com/solar/photovoltaic/best-temperature-for-batteries
Cold Batteries – Freezing Electrolyte
What about freezing electrolyte? This where the classic answer of “It depends” comes it.
The major factor to consider whether electrolyte will freeze or not is the State of Charge (SOC). Most flooded systems have an electrolyte specific gravity of 1.25 to 1.3. If your battery is fully charged (100% SOC) then the expected freezing temperature would be around -92 °F (-69 °C). However, if your battery is sitting at 40% SOC, the freezing temperature would only be -16°F (-27 °C). A fully discharged cell will freeze around 20 °F.
Source: https://www.mathscinotes.com/2013/02/battery-freezing-math/
In the spring (or when the weather warms up), take a moment to look over your batteries to make sure they survived the winter. If they did freeze, physical damage to the jar may have happened.
Cold Batteries – Be Prepared
- Make sure that the heating system is prepared for colder weather
- If your battery system is in an outside structure without heating, make sure your charging system in functioning at 100%
- Ensure that your overall power demands for the battery system can handle a loss in operating capacity.
Let Power Storage Solutions help make sure your DC system is ready for whatever winter throws at you.
Recent Comments