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Lead-Acid Batteries at a Glance (Advantages-Applications-Costs)

February 2, 2012

Lead Acid BatteriesAdvantages

  • Reliable. Over 140 years of development.
  • Robust.
  • Tolerant to overcharging.
  • Low internal impedance.
  • Can deliver very high currents.
  • Indefinite shelf life if stored without electrolyte.
  • Can be left on trickle or float charge for prolonged periods.
  • Wide range of sizes and capacities available.
  • The world’s most recycled product.

Applications

  • Automotive and traction applications.
  • Standby/Back-up/Emergency power for electrical installations.
  • Submarines
  • UPS (Uninterruptible Power Supplies)
  • Lighting
  • High current drain applications.
  • Sealed battery types available for use in portable equipment.

Costs

  • Low cost
  • Flooded lead acid cells are one of the least expensive sources of battery power available.
  • Deep cycle cells may cost up to double the price of the equivalent flooded cells.

Varieties of Lead Acid Batteries

  • Lead Calcium Batteries | Lead acid batteries with electrodes modified by the addition of Calcium providing the following advantages:
  1. More resistant to corrosion, overcharging, gassing, water usage, and self-discharge, all of which shorten battery life.
  2. Larger electrolyte reserve area above the plates.
  3. Higher Cold Cranking Amp ratings.
  4. Little or No maintenance.
  • Lead Antimony Batteries | Lead acid batteries with electrodes modified by the addition of Antimony providing the following advantages:
  1. Improved mechanical strength of electrodes – important for EV and deep discharge applications
  2. Reduced internal heat and water loss.
  3. Longer service life than Calcium batteries.
  4. Easier to recharge when completely discharged.
  5. Lower cost.
  • Valve Regulated Lead Acid (VRLA) Batteries | Also called Sealed Lead Acid (SLA) batteries.

This construction is designed to prevent electrolyte loss through evaporation, spillage and gassing and this in turn prolongs the life of the battery and eases maintenance. Instead of simple vent caps on the cells to let gas escape, VRLA have pressure valves that open only under extreme conditions. Valve-regulated batteries also need an electrolyte design that reduces gassing by impeding the release to the atmosphere of the oxygen and hydrogen generated by the galvanic action of the battery during charging. This usually involves a catalyst that causes the hydrogen and oxygen to recombine into water and is called a recombinant system. Because spillage of the acid electrolyte is eliminated the batteries are also safer.

  • AGM Absorbed Glass Mat Battery | Also known as Absorptive Glass Micro-Fibre

Used in VRLA batteries the Boron Silicate fibreglass mat which acts as the separator between the electrodes and absorbs the free electrolyte acting like a sponge. Its purpose is to promote recombination of the hydrogen and oxygen given off during the charging process. No silica gel is necessary. The fibreglass matt absorbs and immobilises the acid in the matt but keeps it in a liquid rather than a gel form. In this way the acid is more readily available to the plates allowing faster reactions between the acid and the plate material allowing higher charge/discharge rates as well as deep cycling.

This construction is very robust and able to withstand severe shock and vibration and the cells will not leak even if the case is cracked.

AGM batteries are also sometimes called “starved electrolyte” or “dry”, because the fibreglass mat is only 95% saturated with Sulfuric acid and there is no excess liquid.

  • Gel Cell

This is an alternative recombinant technology to also used in VRLA batteries to promote recombination of the gases produced during charging. It also reduces the possibility of spillage of the electrolyte. Prone to damage if gassing is allowed to occur, hence charging rates may be limited. They must be charged at a slower rate (C/20) to prevent excess gas from damaging the cells. They cannot be fast charged on a conventional automotive charger or they may be permanently damaged.

  • SLI Batteries (Starting Lighting and Ignition)

This is the typical automotive battery application. Automotive batteries are designed to be fully charged when starting the car; after starting the vehicle, the lost charge, typically 2% to 5% of the charge, is replaced by the alternator and the battery remains fully charged. These batteries are not designed to be discharged below 50% Depth of Discharge (DOD) and discharging below these levels can damage the plates and shorten battery life.

  • Deep Cycle Batteries

Marine applications, golf buggies, fork lift trucks and electric vehicles use deep cycle batteries which are designed to be completely discharged before recharging. Because charging causes excessive heat which can warp the plates, thicker and stronger or solid plate grids are used for deep cycling applications. Normal automotive batteries are not designed for repeated deep cycling and use thinner plates with a greater surface area to achieve high current carrying capacity.

Source: www.electropaedia.com

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