If you have a boat, golf cart, or backup power supply, you may have noticed that these devices use deep cycle batteries. What are deep cycle batteries, and why do you need them?

A deep cycle battery is designed to discharge a large percentage of its total capacity with each use. Most deep cycle batteries are based on lead-acid battery technologies; a few other designs exist, but they are both more expensive and less efficient than lead-acid designs. Deep cycle batteries are ideal for applications where the battery will be providing some or all of the power to run a particular device.

How Does a Deep Cycle Battery Work?
As with all lead-acid batteries, a chemical reaction between the acid, or electrolyte, and the positive plate creates an electrical current. This current powers whatever devices the battery is connected to before finally being deposited in the negative plate. While the size of the current depends on the surface area of the lead plates, the efficiency and lifetime of the battery are dependent on the thickness of the plates; the plates in starting batteries are thin and spongy to create a high surface area, but the plates of a deep cycle battery are thick and solid.

Maintenance of a Deep Cycle Battery
Depending on the design of the battery, your deep cycle battery may require regular maintenance. Some batteries need to have electrolyte or water added at regular intervals. Other batteries are designed to be maintenance-free; these batteries are easier to care for, but they typically have a shorter life than other batteries.

Charging a Deep Cycle Battery
Before charging a deep cycle battery, make certain that it is safely disconnected from any electrical devices. Next, check the electrolyte level, if appropriate for your battery; the electrolyte should cover the plates completely and must not be frozen. For best results, slowly charge the battery over a period of 10 to 20 hours; use a high-quality charger to regulate the voltage of your charger so that you don't overcharge the battery. After charging, make sure that you disconnect the charger according to your manufacturer's directions to avoid shocking yourself.

Proper Use
While deep cycle batteries are designed to discharge a large percentage of their load with each use, you'll achieve the best performance and life for your battery by limiting each discharge to 50 percent of the battery's capacity. Additionally, if you can limit your discharge to 20 percent of capacity, your battery may last up to five times as long. However, avoid using less than 10 percent of your battery's capacity; smaller discharges can reduce your battery's life.

Disposing of a Deep Cycle Battery
Almost every part of a lead-acid deep cycle battery can be recycled. Most businesses that sell lead-acid batteries, including auto repair shops, will accept old batteries for recycling. Some businesses charge a nominal fee to accept an old battery, but other businesses will actually pay you for your old scrap battery. If you are purchasing a new battery, most businesses will gladly take your old battery and dispose of it for you.