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.)
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.