What is a Deep Cycle Battery?

A battery is generally a device that can store energy. A battery is commonly used to refer to an electrical storage vessel, meaning, it stores electricity for later use.

Batteries are categorized depending on what they are used for (application) and how they are built (construction). AGM, flooded and gelled are the common construction types while marine, automotive and deep cycle are the common application types.

Let’s focus on deep cycle batteries.

Deep cycle batteries typically last for four to eight years, and include boat house batteries, traction, back-up power and PV. Deep cycle batteries have thick lead plates that make the overall surface area lesser. Because of this, there is less chance for chemical reactions to take place and produce less current, but the current produced lasts for longer periods of time.

Industrial deep cycle batteries (traction, fork lift or stationary batteries) are used whenever there’s a need for power that lasts for a longer period of time. Since deep cycle batteries have thick lead plates, they are used in large solar electric systems.

While AGM (Absorbed Glass Mat), automotive and gelled batteries use Lead Calcium plates, industrial deep cycle batteries use Lead Antimony plates. With the use of Lead Antimony plates, the self-discharge rate of batteries is high (1 percent a day for old batteries). The antimony on the plates actually increases water loss that’s why industrial batteries, especially those without hydrocaps, need to be checked for water level from time to time. The antimony not only increases gassing, but also the strength and life of the plate.

Some people use deep cycle batteries as a starting battery. However, an adjustment to the battery size should be made. Yes, it is safe to use deep cycle batteries as a starting battery, but if the size is not adjusted, it can’t get as much cranking amps as a regular starting battery can. It’s also good to note that it is more expensive.

Deep cycle batteries are mostly lead acid batteries that are designed to be discharged from 45 to 75 percent of its capacity, depending on the manufacturer and battery construction. Deep cycle batteries can be cycled down to as low as twenty percent of full charge but manufacturer-recommended cycle is between 45 to 75 percent to increase battery life.

The thickness of the plate is one of the factors that determine how many cycles the battery can do before it dies or loses its capacity. It is also attributed to a battery’s lifespan. The thicker the plate, the longer the battery life. There are of course, other factors that can affect the battery life including temperature, DOD (depth of discharge), and maintenance, among others.

Here are some rough estimates of battery life: (1) AGM deep cycle batteries last for 4 to 8 years, (2) Industrial deep cycle batteries last for 10 to 20 years, and (3) Gelled deep cycle batteries last for 2 to 5 years.

If properly maintained and cared for, deep cycle batteries that are used in renewable energy applications can yield several years of reliable performance.

When it comes to recycling, deep cycle batteries are recyclable. Most materials extracted from the batteries – lead plates and sulfuric acid, among others – are being used to produce new products.