Deep-cycle, lead-acid batteries are widely used in renewable energy and grid-backup system, and are ideally suited for these applications because of their long, reliable life and low cost of ownership. There are many companies that sell deep-cycle lead-acid batteries, so it is important to understand the technologies and other performance factors that affect overall operation and battery life.
Types of Deep-Cycle Battery Technologies
Deep-Cycle Flooded Lead Acid (FLA) Batteries
Deep-cycle flooded batteries are the most popular type in use today in renewable energy systems, and contain electrolyte which fully submerges the plates of the battery. There are several benefits to using flooded batteries, such as lower cost, longer life, easy maintenance, good performance when operating at partial states of charge, and a long, proven history of use.
Deep-Cycle Valve-Regulated Lead Acid (VRLA) Batteries
Deep-cycle VRLA batteries, which include AGM and gel technologies, are designed to eliminate the need for water addition and can be used and installed in any position. They are engineered so that oxygen created by the positive plates during charging can migrate to the negatives plate where it is reduced to water, significantly reducing water loss.
Factors Affecting Cost of Ownership
When buying a deep-cycle battery, there are several factors that should be taken into account to determine the total cost of ownership over the life of the battery.
• Price: A battery with a low price is always attractive, but if this is obtained at the expense of quality and battery life, the cost over time will be high because of the need for frequent battery replacements. That’s why it’s important to consider issues other than price when making the decision.
• Capacity: A battery’s capacity is very important since it is the measurement of the amount of energy stored in the battery.
• Voltage: The battery bank voltage must be considered to ensure it matches the system requirements. The battery bank voltage is often determined by the inverter specifications if installing a DC to AC system, or by the voltage of the loads in a DC system.
• Brand: Choosing a battery from a reputable company is important. Because many companies sell deep-cycle batteries, choosing a company that focuses on deep-cycle technology with a proven history of manufacturing deep-cycle batteries means you will benefit from the company’s expertise.
The Most Important Consideration – Cycle Life
While the factors above are important, the most critical consideration is cycle life, which measures the number of discharge/charge cycles the battery can provide before capacity drops to a specified percentage of its rated capacity. Batteries from different manufacturers may have the same capacity and energy content, and be similar in weight, but design, materials, process, and quality influence how long the battery will cycle.
The nameplate rating on a battery is the fully developed capacity; therefore, testing a battery immediately after it is purchased is misleading since it may take up to 100+ cycles for it to reach its full capacity. Beware of a battery that promises full capacity at the time of purchase or one that reaches full capacity after only a few cycles. Batteries with a 100+ cycle warm-up will always outlast a battery touting a high initial capacity.
As the solar market grows worldwide, the importance of implementing deep-cycle batteries as the energy storage component for renewable energy systems is critical. Because the battery bank in a solar application often represents a considerable percentage of the overall equipment cost, careful attention to proper selection and maintenance of batteries is more important than ever in maximizing return on a deep-cycle battery investment.
By: Dean Middleton, Director of Sales for Renewable Energy at Trojan Battery