A lead-acid battery that is designed to be deeply discharged during use is called a deep cycle battery (DCB). They are re-chargable and meant to be used over and over again.
They differ from starter batteries (CS), like those in an automobile, that are designed to deliver short bursts of high current to crank an engine to start it. They rarely use more than a small portion of their stored capacity. A DCB may be used as a CS, however, with the lower "cranking amps" it puts out, it would generally need to be over-sized.
Deep-cycle batteries are generally 50-80 percent discharged during their normal cycle of use. They may be cycled down to as far as 20 percent but this decreases lifespan and increases cost of replacements. It is not a recommended practice.
As a rule of thumb, 50 percent discharge is the optimum rate to get the best service out of these products. This is linked directly to the number of times they may be charged/discharged over the useful life of the battery.
The main difference between deep cycle and cranking batteries is in the lead plates contained in them. DCB's have thicker plates, high density paste material and thicker separators. These thicker plates resist corrosion through longer periods cycling.
Deep cycle batteries can be found in use just about anywhere. Some common uses include:
* Holding cells for solar panels
* Trolling motors
Flooded batteries lose some electrolyte by evaporation during charging. They must be regularly maintained and inspected with water added as needed.
This problem is largely overcome with SAL (sealed acid lead) type batteries. They are virtually maintenance free. These are the more popular and versatile type of DCB's available today.
Most failures of deep-cycle batteries can be attributed to degeneration of the active material of the plates. Another common fault is corrosion of the internal grid that holds active material.
Storage capacity of a deep cycle battery is usually limited by electrolyte capacity and not plate mass. This improves life expectancy.
There is an environmental impact to be considered with the disposition of discarded units. Most DCB's in the marketplace today are lead acid batteries. They are most often recycled and reclaimed.
These units are recycled at very high rates of recovery:
* 98% by volume, 99.5% by weight
* The plastic cases, lead plates, sulfuric acid, solder, and other metals are 100% recovered for reuse.
* The paper separators that wrap the plates are the only thing not recoverable.
Those are pretty phenomenal numbers in our eco-sensitive society. Recovery rate is 97% industry wide on all lead acid batteries sold in the United States. This results in nearly a closed manufacturing cycle in the this industry.
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