We recently had a customer contact us. She wanted to add more batteries to her system because we are now in a rainy season and have less sun. Typically adding to the battery bank seems to make sense to most. For the past 3 decades this seems to be the obvious solution for most people who are running out of capacity. But this type of thinking is completely backwards. Doubling the size of the battery bank is going to make the problem worse. It ensures that the entire battery bank will fail.

So, let’s break it down. When a solar electric system is designed, we establish what the loads will be. Then we size the battery to the loads. We design the solar panels to be able to charge the batteries based on the amount of sun at that location over the year.

Here is where the thinking goes wrong: If the batteries were properly sized to the load and provide adequate autonomy in the sunny season, the load doesn’t change and the sizing of the battery doesn’t change either. So, what changes? If there is enough solar to keep the batteries charged during the sunny season, but they are unable to keep the batteries charged during the rainy season, then doubling the size of the battery bank is going to make the problem worse.

Obviously there is not enough solar (solar panels) to keep the existing batteries charged during the rainy season. Doubling the amount of solar panels will improve the low-life performance of the system. The more solar you can put facing the sky, the more energy you will collect on cloudy days.

Most solar electric systems were not engineered properly. This is the most common problem for a renewable energy system. Adding more batteries is the worst possible solution. It ensures that the entire battery bank will fail.

If you want to get the most out of your solar electric system, ask us questions! We're here to guide you through all aspects of designing, installing and maintaining a healthy, long-lasting system. Call us at 888-826-0939

Additional info on batteries: See types & sizing of batteriesBatteries For Renewable Energy Systems: 100 Vs 20 Hour Rate, and The Role of Temperature in Battery Life