Introduction
Walk into any battery retailer and you'll find a bewildering variety of options: flooded, AGM, EFB, gel, and even lithium. Each technology has its strengths and ideal applications. Understanding the differences helps you choose the right battery for your vehicle and driving conditions.
This guide explains the major battery technologies available for Australian vehicles, their characteristics, and when to use each type.
Lead-Acid Technology Overview
Most automotive batteries use some form of lead-acid chemistry, a technology over 150 years old but continuously refined:
How They Work
All lead-acid batteries share fundamental chemistry:
Lead dioxide (positive plate) and sponge lead (negative plate)
Sulphuric acid electrolyte
Chemical reactions produce electricity
Charging reverses the reactions
The differences between types lie in how the electrolyte is contained and the plate construction.
Standard Flooded (Wet Cell) Batteries
The traditional design that most vehicles have used for decades.
Construction
Liquid electrolyte (dilute sulphuric acid) freely flows around the plates
Plates are suspended in cells within the case
Vents allow gases to escape during charging
Some designs have removable caps for maintenance
Characteristics
Advantages:
Lowest cost
Proven, reliable technology
Widely available
Easy to manufacture
Can be serviced (if maintainable design)
Disadvantages:
Can spill if tipped
Water loss requires periodic top-up (maintainable types)
Less vibration resistant
Higher self-discharge rate
Shorter cycle life than AGM
Best For
Standard vehicles without start-stop systems
Budget-conscious buyers
Situations where cost is more important than longevity
Vehicles with simple electrical systems
AGM (Absorbent Glass Mat) Batteries
A premium technology that's become increasingly common.
Construction
Electrolyte is absorbed in fibreglass mat separators
No free liquid—the electrolyte is held in the mat
Plates are tightly compressed against the mats
Fully sealed with pressure relief valves
Characteristics
Advantages:
Spill-proof (can be mounted in any position)
Excellent vibration resistance
Very low self-discharge
Faster recharge acceptance
Longer cycle life (can handle deeper discharges)
Better performance in temperature extremes
Ideal for start-stop systems
Disadvantages:
Significantly more expensive
More sensitive to overcharging
Requires compatible charging system
Heavier than equivalent flooded batteries
Best For
Start-stop vehicles
Vehicles with high electrical demands
Performance vehicles with vibration concerns
Vehicles that sit unused for periods
Premium vehicles where reliability is paramount
Vehicles with batteries in hot locations
EFB (Enhanced Flooded Battery)
A middle-ground technology developed for start-stop vehicles.
Construction
Similar to standard flooded but with enhancements
Improved plate formulations
Polyester scrim on positive plates reduces shedding
Better carbon content for improved charge acceptance
Characteristics
Advantages:
Better cycle life than standard flooded
Designed for start-stop applications
Less expensive than AGM
Improved charge acceptance over standard flooded
Good balance of performance and value
Disadvantages:
Not as durable as AGM
Still has liquid electrolyte (can be damaged if tipped)
Limited availability in some sizes
Performance gap compared to AGM in demanding applications
Best For
Entry-level start-stop vehicles
Drivers who want start-stop compatibility without AGM price
Replacement in vehicles that came with EFB originally
Gel Batteries
A specialised technology less common in automotive use.
Construction
Electrolyte is mixed with silica to form a gel
Completely immobilised electrolyte
Similar sealed design to AGM
Characteristics
Advantages:
Excellent deep-cycle capability
Very long service life in appropriate applications
Resistant to vibration
Spill-proof
Tolerant of high temperatures
Disadvantages:
Lower discharge rate (not ideal for starting applications)
More expensive than AGM
Requires specific charging profile
Limited cranking power for size
Best For
Deep-cycle applications (camper trailers, boats)
Accessory power where cranking isn't required
Dual-battery setups for accessories
Applications requiring very long cycle life
Not Recommended For:
Primary starting batteries in most vehicles
High-demand starting applications
Vehicles without compatible charging systems
Lithium (LiFePO4) Batteries
Emerging technology with significant advantages but also limitations.
Construction
Lithium iron phosphate chemistry
Requires integrated Battery Management System (BMS)
Multiple cells in series/parallel configurations
Characteristics
Advantages:
Extremely lightweight (up to 70% lighter than lead-acid)
Very long cycle life (2000+ cycles typical)
Fast recharge
Flat discharge curve (maintains voltage until nearly depleted)
No memory effect
Environmentally more benign
Disadvantages:
Very expensive
Requires compatible charging system (or integrated BMS)
Can be damaged by very low temperatures
Limited starting current for weight compared to lead-acid
Not a drop-in replacement in all vehicles
Best For
Racing and performance applications where weight matters
Motorcycles and recreational vehicles
Specialty applications
Future vehicles designed for lithium batteries
Considerations:
Not yet mainstream for passenger vehicles
May not be compatible with your vehicle's charging system
Requires proper BMS for safety
Calcium Batteries
A term that deserves clarification.
What It Means
"Calcium battery" refers to the alloy used in the plates, not a different technology. Calcium (or calcium-calcium) batteries are flooded lead-acid batteries where both plates use calcium alloy instead of antimony.
Benefits of Calcium Alloy
Lower water loss (often "maintenance free")
Reduced self-discharge
Better resistance to overcharging
Improved corrosion resistance
Common Confusion
Calcium batteries are still flooded lead-acid batteries. The calcium description refers to construction improvement, not a different technology category.
Matching Battery Type to Application
Start-Stop Vehicles
Requirement: EFB or AGM
Standard flooded batteries cannot handle the cycling
AGM preferred for heavy start-stop use
EFB acceptable for lighter-duty start-stop
Standard Vehicles (No Start-Stop)
Options: Flooded, AGM, or EFB
Standard flooded is adequate and most economical
AGM offers premium performance and longevity
EFB offers a middle ground
Vehicles with High Electrical Demands
Recommendation: AGM
Better handles deep discharge/recharge cycles
More consistent voltage under load
Worth the premium for reliability
Vehicles That Sit Unused
Recommendation: AGM
Lower self-discharge rate
Better tolerance of partial state of charge
More forgiving of infrequent use
Classic and Vintage Vehicles
Options: Flooded (often required) or compatible AGM
Some vintage vehicles require specific battery types
Check compatibility before upgrading technology
Cost vs. Value Considerations
Upfront Cost
From lowest to highest:
Standard flooded
EFB
AGM
Gel
Lithium
Total Cost of Ownership
Consider:
Expected lifespan (AGM typically lasts longer)
Warranty coverage
Risk of failure (and associated costs)
Vehicle requirements
When Premium Makes Sense
Invest in AGM when:
Your vehicle requires it (start-stop)
You drive infrequently
You have high electrical demands
Reliability is critical
You keep vehicles long-term
Conclusion
Understanding battery technology helps you make informed choices:
Standard flooded remains a solid, economical choice for basic applications
AGM offers premium performance and is required for many modern vehicles
EFB provides start-stop capability at lower cost than AGM
Gel batteries serve specialised deep-cycle applications
Lithium represents the future but isn't mainstream for starting batteries yet
Match your battery choice to your vehicle's requirements and your priorities. When in doubt, check your owner's manual or consult with a professional.
Quick Selection Guide:
- Start-stop vehicle? → EFB or AGM (required)
- Standard vehicle, budget priority? → Quality flooded
- Standard vehicle, want longevity? → AGM
- Deep-cycle/accessory use? → AGM or Gel
- Weight-critical racing? → Lithium (with proper system)