The Advantages and Disadvantages of Lead Acid Batteries
The lead acid battery was the first rechargeable battery invented for commercial use. Cars, forklifts, and large uninterruptible power supplies [UPS] use flooded lead acid batteries.
Researchers developed maintenance-free lead acid batteries that operate in any position during the mid 1970s. Researchers transformed liquid electrolytes into moistened separators and sealed its enclosure. They also added safety valves to allow gas venting during charge and discharge.
There are two designations of lead acid batteries. They are the sealed lead acid [SLA] battery and the valve regulate lead acid [VRLA] batteries. Lead acid batteries have the lowest energy density among modern rechargeable batteries.
SLA capacity is around 0.2 Ah to 30 Ah. They power portable devices and some wheeled applications. SLA typically power UPS units for personal computers, ventilators, wheelchairs, and small emergency lighting units. SLA are low cost and provide dependable service with minimal maintenance. SLA are used primarily in biomedical and health care industries. Consumers use SLA batteries mainly in portable devices.
VLRA capacity ranges from 20Ah to a few thousand Ah. Manufacturers build large UPS using VLRA for power backup. Cable distribution centers, banks, hospitals, military installations, airports, and internet utilities use VLRA batteries. Consumers use VLRA batteries for stationary applications.
Users cannot charge SLA and VRLA to capacity. Excess charging causes the battery to gas and deplete water. Battery designers build SLA and VRLA batteries with low overvoltage to prevent the battery from reaching its maximum gas-generating potential during a charge.
In the remainder of this article, the focus is on the SLA battery. A SLA battery can float charge for long periods without causing damage to the battery. SLA batteries are not subject to memory. For example, a NiCd battery self-discharges about 40% of its energy stores in about three months. However, an SLA self-discharges about the same amount in one year. SLA batteries are inexpensive but operational costs can be high if full cycles are required on a repeat basis.
The typical charge time of an SLA battery is around 8-16 hours and should be stored in a charged state. Batteries left in discharge state sulfate easier. Sulfation makes battery recharge difficult. SLA batteries do not like deep cycling. Full discharge creates extra strain and a small amount of capacity is lost after each discharge/charge cycle. Once the battery drops to 80 percent of its nominal capacity a recharge becomes more difficult.
An SLA provides around 200 to 300 discharge/charge cycles depending on discharge depth and operating temperature. SLA batteries have a short life primarily because of grid corrosion of the positive electrode, active material depletion, and positive plate expansion. Charging and discharging do not prevent or reverse this trend.
Battery owners can improve SLA performance and prolong its life. The optimum operating temperature is around 77°F. For every 15° rise in temperature the battery’s life cuts in half. So, the higher the temperature the battery stores at the less life it has.
Lead Acid Battery Advantages
-Lead acid batteries are inexpensive. They are simple and easy to manufacture.
-They are durable and dependable. The technology is well-understood, mature, and reliable.
-The self-discharge rates are low. Lead acid batteries self-discharge lower than most rechargeable batteries.
-Low maintenance needed. Lead acid batteries have no electrolyte to fill and no memory. They are capable of high discharge rates.
Lead Acid Battery Disadvantages
-Lead acid batteries can’t be stored in discharged condition
-Poor weight-to-energy density limits. Lead acid batteries have a low energy density. This limits battery use to stationary and wheeled applications.
-Limited full discharge cycles and are best suited for standby applications requiring occasional deep discharge.
-Electrolyte and lead content can cause environmental damage. Lead acid batteries are environmentally unfriendly. There are transportation restrictions on flooded lead acid batteries. There are extra concerns regarding spillage if there is an accident.
-Improperly charged batteries can cause thermal runaway.
Consider a lead acid battery if you want a simple and low maintenance battery for static or mobile use.
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