Lead Acid Battery

old lead acid battery

The Lead Acid Battery is a battery with electrodes of lead oxide and metallic lead that are separated by an electrolyte of sulphuric acid.

The overall reaction is:

PbO2 + Pb + 2H2SO4 <=> 2PbSO4 + 2H2O

Some batteries manufactured for use in very hot or very cold climates may have stronger or weaker acid. If so, it is usually marked on the battery.

Most Lead-Acid batteries will have a specific gravity in the range of 1.1 to 1.3, with most fully charged batteries being about 1.23 to 1.30 (Note: some hydrometers multiply this number by 1000, so 1.3 would read as 1300.)

old lead acid battery

The advantages of the lead acid battery are:

  • Readily available
  • Low cost

The disadvantages are:

  • Low energy density
  • Only average cycle life
  • Can be damaged by deep discharge

Absorbent Glass Mat

A separator technology used in some sealed lead-acid batteries in which the glass-mat separator absorbs 100% of the electrolyte. Because of the immobilized electrolyte, an AGM battery will not leak or spill and does not require water addition.

This battery is used in:

  • deep-cycle and specialty applications
  • telecommunications
  • wheelchairs
  • security alarm systems
  • automotive stop/start hybrids

Automotive Terminal Post – A round post made of lead used on engine starter batteries.

Battery Acid – A solution of approximately 6M sulfuric acid used in the lead storage battery.

Bipolar Lead Acid Battery – Design in which the cells are connected through the plates which each, in turn, act as the current-collector for the positive electrode in one cell and for the negative in the adjacent cell.

Coulombic Efficiency

For a rechargeable battery the fraction of the electrical charge stored during charging that is recoverable during discharge. The coulombic efficiency of a lead acid battery is 0.7 to 0.84 which is poor compared to a lithium ion battery of around 0.95.

Note that the coulometric efficiency is always larger than the energy efficiency.

Deep Cycle – A battery designed to operate over deeper discharges, the normal design change is to use thicker lead plates.

Float Voltage – The voltage at which the battery is floated, or just enough current is supplied to equal the self-discharge of the battery.

For lead acid batteries this is typically about 14.2 volts for a 12 volt battery.

Flooded Cell – A design for lead-acid batteries where the electrolyte is an ordinary liquid solution of acid.

Gel Cell – A technique for sealed lead-acid batteries. The electrolyte solution is in a gel form, usually silica gel, instead of plain liquid.

L-Post – A style of battery terminal, shaped like an L, with a flat vertical part to which the cable is bolted.

Peukert Equation – A formula that shows how the available capacity of a lead-acid battery changes according to the rate of discharge.

Plates – The metal plates, usually lead or lead compound, immersed in the electrolyte in a battery.

Sealed Battery – A battery which can be operated without regard to position. This type of battery has a captive electrolyte and a resealing vent cap, also called a valve-regulated battery. Electrolyte cannot be added.

Spiral Wound Lead Acid Battery – Instead of having the electrodes as flat plates, the electrodes are rolled up in a spiral.

Stratification – A condition in which the concentration of acid is greater at the bottom of the battery than at the top. This is normally caused by continued undercharging.

Sulfation – The accumulation of lead sulfates on the plates of a lead-acid battery. When enough plate area has sulfated, the battery will not be able to provide enough current and will normally need to be replaced.

Universal Terminal Post – A style of battery terminal, with a round post similar to the automotive post, but with a threaded stud in the center of the post.

Valve Regulated Lead Acid Battery (VRLA) – This type of battery uses pressure valves that open only under extreme conditions. VRLA batteries are sometimes called recombinant batteries.

Vented Battery – A battery in which the gaseous products of electrolysis and evaporation are allowed to escape into the atmosphere as they are generated. These batteries are commonly referred to as Flooded Batteries.

About Nigel 279 Articles
Have been making models since I was around 7 years old and using a lathe from the age of 11, a self taught engineer with a passion for making model engines.

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