If you ever own anything that says it requires deep cycle batteries, do not ignore the warnings advising you to use those specifically. Not all batteries are the same, as many things and machines use what are instead called starter batteries. Starter batteries are common in cars, where they give short yet intense bursts of power in order to get an engine cranked and going.
Deep cycle batteries are different. They discharge almost half to three quarters of their power reserve in order to get the attached equipment running and going. As such, these batteries are of a lead-acid design, and often oversized and heavy.
Keeping a deep cycle battery going over a long life span can sometimes be a little tricky. The massive discharges can drain the battery over time. To keep a deep cycle battery operating optimally for a long time, then it is best to set things up so that a battery never dips below twenty percent of its reserve, and that the initial burst is more towards the forty five percent range and not three quarters.
The uses of deep cycle batteries are not uses that everyday citizens would likely make personal use of in their normal lives, but there are uses all around that people would recognize. Traffic signals often use these kinds of batteries, as do UPS power supplies for computers and sump pumps.
A very common use of deep cycle batteries is in motorized equipment. Motorized wheelchairs often use deep cycle batteries, as do golf carts, and electrically-propelled industrial street sweepers and forklifts are common applications for such batteries. There are many marine uses too in fishing boats and other aquatic craft.
Other common applications include energy-independent systems on land, such as highway rest stops or structures needing electricity when far removed from a municipal power grid. Solar power systems also use deep cycle batteries to collect sunlight all day and then store the power for use at night or in cloudy weather.
If any of these situations is a part of your life, be it working on a forklift, a friend or family member with a motorized wheelchair, or you own a UPS system, a boat, or a solar power system, you might have a deep cycle battery somewhere near you. If it ever needs repair or maintenance, then make sure you replace it with another deep cycle battery and do not treat it as a starter battery, lest the equipment not work in the future.