How to Maintain and Care for Deep Cycle Batteries

Deep cycle batteries are essential for most off-grid power systems, as they can withstand repeated discharging and recharging cycles without damaging their cells. These batteries come in various chemistries, architectures, and maintenance requirements, and they are significantly more expensive than ordinary car batteries. Therefore, proper and regular maintenance is crucial to enhance their longevity.

Modern battery systems often use automated management controls to monitor voltage and charge regulation. However, some tasks, such as topping up water in flooded batteries, still require on-site presence. Lithium-ion batteries, on the other hand, need minimal human intervention.

Regardless of the type of deep cycle batteries you have, this guide will help you keep your setup running optimally. Read on to discover how to avoid common problems related to battery banks.

Size Your Battery Banks Correctly

Proper battery bank sizing is crucial for determining the specifics of an off-grid energy system. It involves selecting a battery that can handle the load from the power source and supply enough power to all appliances consistently without discharging to unhealthy levels. When sizing, consider a load larger than your current energy requirements, as your needs will increase over time. Adding new batteries to an old system is not advisable due to varying voltage responses and potential losses.

Program the Battery Charger

Initial programming of chargers is essential to ensure your battery bank charges at the recommended voltage and current. Set the voltage applied to the battery during the bulk, absorb, and float phases of charging. The bulk phase supplies high current to refill charge and raise voltage rapidly. The absorb cycle slows down the charging rate when the battery is 80 to 100 percent full. During the float phase, a trickle charge keeps the battery bank at full state of charge (SOC). Correct parameters allow the batteries to charge optimally, maintaining their health.

Charge the Batteries Fully Periodically

To prevent cell degradation, bring your batteries to a full state of charge every three weeks. While the system may achieve this automatically, it's essential to ensure it happens. Full charges prevent internal corrosion and enhance cell equalization, boosting battery health.

Avoid Parallel Battery Strings

The best battery bank configuration consists of a single series of batteries. Avoid installing more than three battery strings in parallel, as this setup loses equalization and accelerates the deterioration of weak cells. Detecting weak cells is challenging because surrounding ones compensate for them, leading to system failure and costly repairs.

Maintain Moderate Temperatures

Heat is detrimental to virtually all types of batteries, causing them to lose about 25 percent of their capacity at 30°F. The effect is more severe at higher temperatures. Keep your deep cycle batteries in a moderate temperature zone, away from radiant heat sources, or install an earth-sheltered enclosure. Temperature compensation is vital due to random heat variations. Hot conditions require a decrease in charge voltage limit to avoid overcharging, while cold conditions require an increase to reach full charge. Most power centers, charge controllers, and backup chargers come with temperature compensation features.

Prevent Corrosion

Corrosion of terminals and cables is a common issue in flooded battery installations, causing electrical resistance and other hazards. Prevent it by applying a non-hardening sealant to the terminals before assembling your battery bank. Coat the wire lugs, nuts, and bolts entirely. If applying to an existing setup, corrosion will begin as soon as acid or water contacts uncovered metal parts. Use compounds designed to protect battery terminals or household petroleum jelly, applying a thin layer on exposed parts without hindering electrical contact.

Clean the Battery Top Occasionally

Acid spatters or dust on the surface of your deep cycle batteries make the setup untidy and increase corrosion and stray current flow, wasting energy. Properly sealed batteries can be rinsed with a wet cloth twice a year. Avoid using too much water to prevent short circuits, and wipe the surface dry after cleaning.

Install Low-Voltage Disconnects

A total battery drain can cause permanent capacity loss and lifespan reduction. Ensure your system's load circuits include a low voltage disconnect (LVD) feature. Many charge controllers and inverters have this component built-in. If not, purchase one to save your deep cycle batteries from accidental severe discharging.

Add Water to Flooded Batteries

For wet-cell or flooded batteries, keep the plates submerged in the electrolyte. Inspect the acid level and add distilled or deionized water if it falls below the recommended amount. Avoid topping up discharged batteries, as they absorb the electrolyte when draining charge, potentially causing excess liquid once recharged. Charging batteries produce hydrogen, so avoid tampering with cables to prevent explosions and fires.

Final Thoughts on Deep Cycle Batteries

Deep cycle batteries are indispensable for off-grid power systems, powering homes, recreational vehicles, and marine vessels. While they require attention for smooth operation, maintenance doesn't have to be stressful. With correct installation and knowledge of necessary upkeep procedures, they can serve you smoothly for years. Various versions, such as flooded, absorbed glass mat (AGM), and gel batteries, exist, and the maintenance tips provided apply to most deep cycle batteries.

If you're looking to install a battery bank, we're here to help. Contact us for supplies and expert advice on everything related to deep cycle batteries.