Are Your Batteries Ready for Winter?

Well, winter is around the corner at the ranch, and with winter comes the cold air and cloudy days. Even though our panels like the cold air (as noted in a previous article), exactly the opposite is true of lead acid batteries. Batteries definitely do not like the cold weather. The ideal weather for lead acid batteries is 80º. At that temperature, they charge, discharge, and produce their highest AH (amp hour) capacity. In this cold weather, we run into two specific problems.

The first and most common issue is longer charge times and lack of performance or AH production. To calculate the performance difference, you can use the formula of 10% loss of performance for every 15º below 80º. If your batteries are insulated and in a battery room and can even stay at 45º to 50º (close to the daytime average high), you are still only getting about 80% of their normal performance in best cases. But put those batteries on a shelf in a non-insulated shed or open shelf outside where it drops to 20º this time of year, and you have now dropped the performance to 60%. And that is if you have them 100% charged, which is hard to do with days on end of cloudy weather.

The second problem is freezing the batteries. A fully charged battery will not freeze until about 80º below zero. But a discharged battery can freeze, bulge, and possibly even crack the housing at about 20º, completely ruining the battery and creating a very dangerous situation. 

To prevent this from happening and having to spend big bucks to replace your batteries, there are two key things to do. First buy or build an insulated battery box. Even if this box sits outside, if it is enclosed and insulated you will greatly increase the life of your batteries. Remember that batteries do off gas, so install a couple of vents to prevent gas build up. Second, keep track of your battery state of charge. This is a two-part process: First, be sure you are Equalize charging your batteries in the winter months at least once every 30 days per manufacturer recommendation. Second, test the specific gravity to verify they are charged. One note about testing specific gravity on a cold battery - for every 10º below our ideal 80º set point, you need to take (0.004) off your test result. As an example, if you test the battery at 1.277 but it is 50º, then you need to deduct (0.012) - your test result would be 1.265. 

We know these processes get really technical and hard to understand. So, please feel free to call us with questions. Remember, a warm, fully charged battery will keep you nice and warm this winter. So, take care of your batteries.