Initial Capacity vs Rated and Peak Capacity for Deep-Cycle Batteries

Deep cycle batteries are designed to provide continuous power over an extended period of time and are then recharged in preparation for the next discharge/recharge cycle.  For many industrial and consumer applications where energy storage is critical, flooded lead-acid batteries provide premium performance at an unrivaled cost.  Consumers, however, may not be aware that flooded lead-acid deep cycle batteries are designed to reach their rated and/or peak capacity after a conditioning period of capacity ‘cycle-up’.  This cycle-up period consists of a series of discharge/recharge cycles in normal operation during which the available battery capacity increases with each cycle.  This conditioning cycle-up period is designed to provide the optimum in cycle life vs. cost for this type of battery and application.  The number of cycles required to achieve rated and/or peak capacity depends on many factors, including but not limited to battery design, recharge method, depth of discharge, temperature, etc.

Most deep cycle battery manufacturers provide a ‘Capacity Development Curve’ that describes the relationship of initial capacity and the number of cycles required to achieve rated and/or peak capacity for this type of battery.  The test procedures used to determine battery capacity ratings and capacity development relationships are specified in Battery Council International procedure BCIS-05 BCI Specifications for Electric Vehicle Batteries (Rev. 2010-15).  Per BCIS-05: “Long-life deep cycle EV batteries typically exhibit 75-80% of rated capacity on initial discharge, full rated capacity within the first 100 cycles, and >100% of rating at peak capacity.”

To achieve optimum cycle life vs. battery acquisition cost, most battery manufacturers recommend sizing the battery’s capacity to ~50% depth of discharge (DOD).  This not only optimizes the cycle life of the battery vs. cost but also provides a ‘reserve’ capacity in situations where additional runtime is needed beyond normal requirements.  Since flooded lead-acid deep cycle batteries can continue to deliver useable capacity down to ~50% of rated capacity, this recommendation also allows utilization of the total number of cycles available from the battery.  For these reasons, the fact that this type of battery does not deliver full rated capacity ‘out-of-box’ is not usually an issue and can easily be managed through proper battery sizing and choice of battery type and manufacturer.

Battery manufacturers do recognize that fleets operating battery-powered machinery such as aerial platform lifts, floor cleaning machines, pallet jacks, and golf carts desire the highest possible capacity over the life of the battery.  Accordingly, they are constantly improving battery designs and charging methods to achieve the highest possible initial capacity and the fastest possible cycle-up without compromising overall cycle life.



Battery Industry Associations Commit to Increase Global Recycling Efforts

While North America and Europe have a lead recycling rate of more than 99 percent, industry trade associations met among concerns that these rates were not the same in other parts of the world. In order to improve lead recycling efforts globally, the International Lead Association (ILA), Association of European Automotive and Industry Battery Manufacturers (Eurobat), Battery Council International (BCI), and the Association of Battery Recyclers (ABR), created a Memorandum of Cooperation outlining a framework for the development of a material stewardship program designed to support the environmentally responsible management of lead and other compounds, throughout the lifecycle of a lead-acid battery, from raw material production through battery manufacturing and recycling.

The memorandum issued by all four industry trade associations demonstrates an understanding that lead batteries used for energy storage, industrial applications, and in vehicles is worldwide, but improper recycling practices can cause health risks to the public and environment in areas where recycling rates are not as high as those in North America and Europe. In an effort to respond to these issues, these trade associations agreed collectively to address them by adopting a common set of principals, establishing continuous improvement goals, participate in knowledge transfer concerning environmentally responsible management of lead batteries, and to provide progress reports to interested shareholders.

The effort, according to the ILA, will help to advance environmentally responsible production and recycling of lead and lead batteries, in which the industry sees a global demand for this type of energy storage to increase thirteen-fold by 2024. More information on the agreement by the four trade associations and quotes can be found on the ILA website.

US L16HC XC2 Deep Cycle Battery

A Solar Energy Battery Storage Bank Made To Last 16 Years

Low Amperage Draw And Impeccable Maintenance Kept A Battery Energy Storage Bank Operable For More Than A Decade

Grover, Wyoming resident Jody Jenson, isn’t living “off-grid,” but his home is in a rural part of the state, where water comes from a well and delivered to the home by electric pumps. After several power outages, he didn’t want to rely on the city’s power grid to have fresh water, so he built a 48-volt solar system with U.S. Battery Deep-Cycle batteries for energy storage that have provided 16-years or reliable service.  “I did not like the vulnerability of relying on the grid for our drinking water,” said Jenson. “I spent over $12,000 on this system, including digging a new 100-ft. well. It definitely wasn’t to reduce costs, but more about having freshwater availability.”

To supply power to the pump system Jenson utilizes four 120-watt solar panels mounted together and wired to provide 24-volts and is connected to a circuit breaker and charge controller.  To store energy, he uses eight US L16HC XC2 batteries. “The system powers the well-pump that draws 4-amps, depending on groundwater level, but it’s pretty consistent,” he says. “It takes about 18-hours to fill the 1200 gallon cistern. The system normally runs about 12-hours between low and full tank levels.  From the cistern, there’s another pressure pump that draws six amps for approximately three minutes after starting, providing roughly 30-gallons between cycles.”

 Even though the system doesn’t draw huge amounts of amperage, Jenson never expected that the US L16HC deep-cycle batteries would last 16-years. “When I bought them, I remember being told that with proper maintenance, they should last something like five years,” said Jensen. “I knew with care, they would last longer.”

Jenson has taken exceptionally good care of his deep-cycle batteries, demonstrating how cost-effective flooded lead-acid batteries can be with proper maintenance. His routine includes weekly and monthly procedures. “Every week I go to check the system, including the water level in the cistern, corrosion on the battery posts, charging rate,  and battery voltage,” he says. “The batteries are still showing 26.5-volts fully charged. Once a month, I also check battery water levels and the amperage draw of the two pumps. This gives me any clues as to any problems that might be occurring. Quarterly, I add distilled water to the 24 individual cells.” 

While most people would consider this an impeccable maintenance routine, Jenson also includes periodic equalizing charges. “After adding water, I equalize the bank of batteries with the charge controller for a period of two hours at a maximum of 16-amps,” says Jensen. “I have never equalized without the batteries being fully charged. I’ve totaled up all the water I have added over the years, and as of today, from February of 2003 to now, I’ve added 63-gallons of water to the 24-cells!”

In addition to Jensen’s unique system and maintenance procedures, U.S. Battery L16 HC deep-cycle batteries feature the company’s XC2 formulation that uses Diamond Plate technology, highly efficient synthetic tetrabasic lead sulfate (TTBLS) crystal structures that enhanced performance, charging, and extend battery life. U.S. Battery also manufactures a line of Renewable Energy Batteries that are specifically designed for energy storage and feature Defender Moss Shields that reduce mossing and sulfation conditions, and Outside Positive Plates that mitigate the effects of plate sulfation.

While receiving 16-years of service from a set of deep-cycle batteries is not common, Jenson’s theory of having a large battery bank with a relatively low amperage draw, does demonstrate what low depth-of discharge and proper maintenance procedures can do to extend the life of deep-cycle batteries used for energy storage.