Battery Technologies

Battery Technologies Used in Overland Vehicles

Battery selection is one of the most important design decisions in any overland or camper build. The type, capacity, and management of your battery bank determine how long you can stay off-grid, what appliances you can run, and how safely your system operates. This guide outlines the most common battery chemistries used in vehicle-based power systems and compares their advantages and disadvantages.

Overview

Overland and expedition vehicles rely on **deep-cycle auxiliary batteries** to power lighting, fridges, inverters, and other 12V or 24V equipment. Unlike starter batteries (which deliver short bursts of current to start an engine), deep-cycle batteries are designed to discharge and recharge repeatedly without damage.

Common battery chemistries include:

• **Flooded Lead-Acid (FLA)**
• **Absorbed Glass Mat (AGM)**
• **Gel Cell**
• **Lithium Iron Phosphate (LiFePO₄)**

1. Flooded Lead-Acid (FLA)

Traditional lead-acid batteries use liquid electrolyte and removable caps for maintenance.

Advantages

• Low initial cost and widely available.
• Proven and robust in many environments.
• Tolerant of simple charging systems.

Disadvantages

• Requires regular topping-up and ventilation (risk of gas emission).
• Loses capacity if deeply discharged frequently.
• Heavy for usable energy; typically only 50% of capacity is usable.
• Must be installed upright.

Best for: Budget-conscious builds or where simplicity and serviceability are priorities.

2. Absorbed Glass Mat (AGM)

AGM batteries immobilise the electrolyte in a fibreglass mat, making them spill-proof and vibration resistant.

Advantages

• Maintenance-free and safe for interior mounting.
• Lower internal resistance → faster charging.
• Better tolerance for vibration and cold starts.
• Moderate cost with good availability.

Disadvantages

• Sensitive to overcharging; requires correct voltage regulation.
• Still heavy and limited to ~50–60% depth of discharge.
• Shorter cycle life than lithium (typically 300–500 cycles).

Best for: Reliable mid-range systems with alternator charging and moderate power demands.

3. Gel Cell

Gel batteries suspend the electrolyte in a silica gel.

Advantages

• Fully sealed and leak-proof.
• Tolerates deep discharge better than FLA or AGM.
• Performs well in warm climates.

Disadvantages

• Must be charged carefully — too high voltage causes irreversible damage.
• Higher cost and lower current output (not ideal for heavy inverter loads).
• Limited availability in large capacities.

Best for: Light off-grid campers with solar charging and modest loads.

4. Lithium Iron Phosphate (LiFePO₄)

The modern choice for most new overland and expedition builds. Lithium cells provide high energy density, long cycle life, and excellent efficiency.

Advantages

• Lightweight (around half the weight of lead-acid for equivalent usable energy).
• 80–90% usable capacity without damage.
• Long lifespan — 2000–5000+ cycles.
• Fast charging and flat voltage curve.
• Maintenance-free and safe when used with a proper BMS (Battery Management System).

Disadvantages

• Higher upfront cost.
• Requires compatible charging equipment (alternator, solar, mains charger).
• Poor performance in sub-zero charging conditions (unless heated or managed).
• More complex installation — requires BMS and protection circuits.

Best for: Serious overlanders and long-term off-grid systems where efficiency and weight savings justify the cost.

Battery Comparison Summary

Type	Usable Capacity	Weight per kWh	Typical Lifespan (cycles)	Maintenance	Approx. Cost (per Ah)
Flooded Lead-Acid	~50%	Heavy	200–400	High	£
AGM	~55%	Heavy	300–500	Low	££
Gel	~60%	Heavy	400–700	Low	££
LiFePO₄	~90%	Light	2000–5000+	None	££££

Installation Considerations

• Use proper cable sizes and fusing for high current loads.
• Fit a battery monitor or shunt to track real-time usage.
• Keep batteries within recommended temperature range.
• Secure battery banks firmly and allow ventilation (except sealed lithium units).
• Never mix different battery types in the same bank.

See Also

• Inverters and Mains Power in Overland Vehicles
• Solar Charging Systems
• 12 Volt Wiring and Fusing
• Battery Management Systems (BMS)

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Always follow manufacturer specifications for charge voltages and safety requirements. Incorrect charging or wiring can shorten battery life or cause damage.