Focusing on the deep cycle battery used in marine applications, I think it is important to say that this type of battery has some specific maintenance requirements as compared to the automotive type that most people are accustomed to working with. A multiple stage deep cycle battery charger is required for proper re-charging of deep cycle batteries as compared to the single stage charger used for automotive battery care. The deep cycle battery typically will not reach its maximum storage capacity until after numerous charge/discharge cycles. The deep cycle is designed to be greatly discharged and then completely recharged again many times during its service life. Discharging an automotive battery completely even once can cause permanent failure. It is best to use a quality multiple stage charger with a minimum of 8 amps output and around 16 amps on the high side. Buy purchasing a deep cycle charger that also has a built in “float mode” you can keep your marine battery fully charged for long periods of time when not in use and can also greatly increase the service life of the unit.
Even when new, the deep cycle battery needs an initial first charge before being placed into service. In fact, a new battery typically requires between twenty to fifty charge/discharge cycles before it will reach its maximum storage capacity. You should break the battery in gradually during this period and avoid totally depleting the new battery. Doing so can reduce the batteries service by months or even years. Keeping your battery clean is a much overlooked maintenance technique, but one that needs doing. When residues build up on the top surface of the battery they can provide a “circuit” between the positive and negative terminal and provide an opportunity for the battery to discharge. You should clean the battery posts or terminals annually with a wire brush and coat the terminals with a thin coat of grease to prevent oxidation. Inspection of the battery case is a visual task and should also be done annually or in the event that the battery is dropped or struck by an object. Securing your battery in a battery box on your boat provides an added measure of security for both you and the battery.
A process known as “equalizing” should be performed on your deep cycle battery periodically. This process is accomplished by providing a low current charge for an extended period of time after the normal charging cycle has been completed. The batteries cells are kept in balance so that they all perform equally during use. This equalizing process needs to be part of your regular weekly maintenance routine during the boating season. Bringing the battery to a fully charged condition should be done at least every three weeks. As a precautionary measure, you are encouraged to employ a low voltage disconnect device in your power circuit. This will automatically disconnect the battery from the circuit if internal voltage drops too low. Using a battery that it is in an under voltage condition will limit its useful life. For maximum service life, it is always a good idea to purchase a battery that is a size larger than your application requires and to purchase a good quality battery rather than a generic, less expensive battery.
Following a regular battery maintenance routine will help to extend the useful life of your expensive marine deep cycle battery and saves you money in the long run. Using a charger specifically designed for deep cycle batteries is a must, and even a brand new battery requires initial charging and inspection prior to being put into service. With proper care, your deep cycle battery can provide up to 15 years of dependable service and get you back to shore every time.