Types of Batteries

Deep cycle

Cranking (Starting)

A lead-acid battery is composed of a series of plates immerse in a solution of sulfuric acid. Each plate consists of a grid upon which is attached the active material (lead dioxide on the negative plates, pure lead on the positive plates.) All of the negative plates are connected together, as are all of the positive plates.

When the battery is discharged (when it is subjected to an electrical load), acid from the elecrolyte combines with the active plate material. This releases energy and converts the plate material to lead sulfate. The electrolyte become less acidic in the process, and the specific gravity of the solution drops.

When a battery is recharged, the opposite occurs: the lead sulfate reverts back to active material, and the electrolyte becomes more acidic with a higher specific gravity.

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Sulfation: the number one cause of battery failure

To recharge a lead-acid battery, it is necessary to convert the lead sulfate material which attaches to the discharged areas of the plates back to active plate material.

If the battery has not remained discharged for long or has only been discharged slightly, this is a relatively easy process. However, when the battery has remained discharged for an extended period or has been subjected to repeated deep-discharges without charging fully between cycles, the sulfate material can harden into crystals which are more difficult to convert. Until the sulfate is converted, the sulfated portions of the plates are useless, and the battery can accept and hold only a partial charge. Eventually, sulfation can ruin a battery.

Sulfation is the number one cause of battery failure.

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Lead acid batteries fall under two general categories: cranking (starting) and deep-cycle. Cranking, or starting, batteries are designed to give short, high energy bursts for high load applications such as engine starting. Cranking batteries have many thin plates to maximize the plate area exposed to the electrolyte and thereby maximize the energy available. Cranking batteries are not appropriate for extended use since disharging the battery deeply can rapidly destroy the thin plates

Deep-cycle batteries are designed to withstand the rigors of repeated deep discharge cycles, and are most appropriate for providing sustained, low amperage current, such as in many marine or RV applications. Deep-cycle batteries are designed with thicker, sturdier plates and active material.

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Extending the useful life of a battery depends largely upon proper charging techniques. Since sulfation is the number one cause of battery failure, the charging method you choose should be effective in reducing sulfation problems. Rule of thumb: whenever possible, bring any batteries up to full charge as slowly as possible. This slow charging process is also known as equalization. Equalization allows the elctrolyte time to diffuse into the less accessible areas of the plate grid and convert those areas from lead sulfate to active plate material.

Deep-cycle batteries are especially susceptible to sulfation damage due to repeated discharges. Equalizing a deep-cycle battery periodically and keeping it fully-charged between uses will greatly extend its useful life.

Infrequently-used or stored batteries are also prone to sulfation if not kept fully-charged between uses. A battery loses approximately 1 percent of its charge per day (up to 2 percent in hotter climates) due to self-discharge. If self-discharge is not compensated for, a stored battery can become sulfated and will eventually be ruined.

The second most common cause of battery failure is overcharging. Many chargers on the market will damage your battery if left attached for extended periods by "boiling" the water out of the electrolyte solution. Eventually, water loss will destroy a battery. Checking the electrolyte level in a battery--and adding distilled water when necessary--is extremely important, especially when using fast chargers or many of the trickle chargers on the market

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