A deep-cycle battery is a lead-acid battery designed to be regularly deeply
discharged using most of its capacity. In contrast, starter batteries are
designed to deliver short, high-current bursts for cranking the engine, thus
frequently discharging only a small part of their capacity. While a deep-cycle
battery can be used as a starting battery, the lower "cranking current"
imply that an oversized battery may be required.
A deep-cycle battery is designed to discharge between 45% and 75% of its
capacity, depending on the manufacturer and the construction of the battery.
Although these batteries can be cycled down to 20% charge, the best lifespan vs
cost method is to keep the average cycle at about 45% discharge. There is a
direct correlation between the depth of discharge of the battery, and the number
of charge and discharge cycles it can perform.
Structure Deep-cycle lead-acid batteries generally
fall into two distinct categories; flooded and valve-regulated lead-acid,
with the VRLA type further subdivided into two types, Absorbed Glass Mat and
Gel. The structural difference between deep cycle batteries and cranking
batteries is in the lead battery plates. Deep cycle battery plates have thicker
active plates, with higher-density active paste material and thicker
separators. Alloys used for the plates in a deep cycle battery may contain more
antimony than that of starting batteries. The thicker battery plates
resist corrosion through extended charge and discharge cycles.
Applications Cathodic protection, which might include
marine use Other marine use, especially on a
sailboat lacking power generation capability, generally smaller vessels
Trolling motors for recreational fishing boats
Industrial electrically-propelled forklifts and floor sweepers
Motorized wheelchairs Off-grid energy storage systems for
solar power or wind power, especially in small installations for a single
building Power for instruments or equipment at
remote sites Recreational vehicles
Traction batteries to propel vehicles, such as golf carts, and other highway
electric vehicles Traffic signals
Uninterruptible power supply, usually for computers and associated equipment,
but also sump pumps Audio equipment, similarly to a UPS but
also in certain 'clean power' devices to supply clean D.C. power isolated from
the public electric supply for inversion to A.C. to maximize audio signal
reproduction Flooded
The term "flooded" is used because this type of battery contains a quantity of
electrolyte fluid so that the plates are completely submerged. The electrolyte
level should be above the tops of plates which serves as a reservoir to make sure
that water loss during charging does not lower the level below the plate tops and
cause damage. Flooded batteries will decompose some water from the
electrolyte during charging, so regular maintenance of flooded batteries
requires inspection of electrolyte level and addition of water. Major modes of
failure of deep-cycle batteries are loss of the active material due to shedding
of the plates, and corrosion of the internal grid that supports active
material. The capacity of a deep cycle battery is usually limited by
electrolyte capacity and not by the plate mass, to improve life expectancy.
Recycling The vast majority of deep cycle
batteries on the market today are lead acid batteries. Lead acid batteries are
recycled 98% by volume, 99.5% by weight. The plastic cases, lead plates, sulfuric
acid, solder, and other metals are 100% recovered for reuse. The only part of a
battery that is not recyclable is the paper separators that wrap the plates.
Due to the acid bath the paper sits in, the fiber length is reduced so far that
it cannot be rewoven. Industry wide, there is a greater than
98% rate of recovery on all lead acid batteries sold in the United States,
resulting in a virtually closed manufacturing cycle.
See also Desulfation
Electric vehicle battery Gel battery
VRLA battery References
External links The difference between deep-cycle
batteries and regular lead-acid batteries at HowStuffWorks
Northern Arizona Wind & Sun Deep Cycle Battery Overview
Battery Council International Car and Deep-Cycle Battery FAQ 7.0
How To Choose Deep Cycle Tubular Battery Deep cycle and AGM information