How to Maintain a Solar Battery Bank

Grid tied solar setups can connect to an existing electric grid. When the solar panels provide excess energy, that energy is returned to the grid. On days when energy demand is more than the panels provide, the panels can draw energy back from the grid. Solar setups that are not grid tied generally rely on battery banks, which must be maintained so they can store energy for use at night or on cloudy days.

Difficulty: Moderate

Instructions

1. Match the battery bank size to the solar panel array. Determine your load requirements, and build a battery bank large enough to store five days' worth of power plus another 30%. The 30% will allow for fluctuations in battery capacity due to temperature and other factors.

2. Don't skimp when you buy your batteries. Cheap batteries will only last about half as long as high-quality deep cycle batteries, which should last five to 15 years. The more expensive batteries save money in the long run.

3. Set up a simple battery string using the largest capacity batteries you can afford. Higher capacity means thicker plates, which means a longer lifespan for your battery bank.

4. Prevent corrosion with a sealant. You can buy a commercial sealant, but good old petroleum jelly does the trick just fine. Apply the jelly or sealant to your terminals before you assemble the battery bank. Otherwise, the sealant will not reach all the nooks and crannies, and they will corrode.

5. Maintain an even temperature. Batteries lose storage capacity incrementally the lower the temperature drops. At 30 degrees Fahrenheit, a battery bank will lose 25% of its storage capacity. However, at higher temperatures, batteries begin to deteriorate. The ideal temperature range for a battery bank is 65 to 75 degrees Fahrenheit.

6. Top off, or fully charge, your batteries once every three weeks or so. This will equalize all the batteries in the battery bank, preventing weak batteries from losing even more power. Topping off your battery bank will also prevent internal corrosion and increase the life of your battery bank. Use an amp-hour meter to determine if your batteries are topped off.

7. If you use flooded batteries, check their water levels every 6 to 12 months. All the cells in your flooded batteries must be covered by water. If you must add water, use distilled or deionized water. Do not overfill your flooded batteries.

Tips & Warnings

• Wear goggles or safety glasses when working with your batteries. The battery acid is dangerous. Keep a box or bag of baking soda on hand to spread on battery acid spills.
• Adding water to sealed batteries can destroy your battery bank.