A deep-cycle lead-acid battery is designed to deliver a consistent voltage as the battery discharges. In contrast, starter batteries (e.g. most automotive batteries) are designed to deliver sporadic voltage spikes. Battery-driven vehicles, such as golf carts, forklifts and floor sweepers commonly use deep-cycle batteries. While a deep-cycle battery can be used as a starting battery (and may work better than a traditional starting battery with the myriad of electronic components attached to most modern vehicles), the lower "cranking amps" imply that an oversized battery may need to be used in an older vehicle that lacks fuel injection. Deep cycle batteries can be charged with lower amps than regular batteries.

The key structural difference between deep cycle batteries and cranking batteries is the Lead plates, which are solid in deep-cycle batteries and composed of porous sponge-like plates in starting batteries. Some batteries that are labelled "deep-cycle" do not possess these solid lead plates, however, and are actually "hybrid" batteries. While a deep-cycle battery is designed to discharge down to as much as 20% of its charge capacity over several cycles, companies recommend that a hybrid battery not be discharged beyond 50% of its capacity


The lifespan of a deep cycle battery will vary considerably with how it is used, how it is maintained and charged, temperature, and other factors. In extreme cases, it can vary to extremes - we have seen L-16's killed in less than a year by severe overcharging, and we have a large set of surplus telephone batteries that sees only occasional (5-10 times per year) heavy service that are now over 25 years old. We have seen gelled cells destroyed in one day when overcharged with a large automotive charger. We have seen golf cart batteries destroyed without ever being used in less than a year because they were left sitting in a hot garage without being charged. Even the so-called "dry charged" (where you add acid when you need them) have a shelf life of 18 months at most. They are not totally dry - they are actually filled with acid, the plates formed and charged, then the acid is dumped out.

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