Assessing Hybridisation Pathways for Legacy Fleet of General Service 4x4 vehicles

Background

The UK Ministry of Defence (MoD) launched an initiative to evaluate electric vehicle technologies for military use. As part of this program, four in-service British Army Defenders were successfully converted from diesel to full electric operation using reversible drop-in kits. The results from these conversions support future fleet modernization strategies as the 2030 obsolescence milestone approaches.

Project Objective

To identify viable hybrid powertrain options that extend vehicle range and address charging limitations found in fully electric variants. The MoD sought hybrid configurations capable of matching the range and power performance of the diesel Defender while maintaining compatibility with existing export power requirements of 30 kW.

Approach

The project began with the detailed characterization of both internal combustion engine (ICE) and battery-electric (BEV) Defender powertrains. Using this data, ePOP engineers developed system-level models to assess hybrid configurations based on scalability, component sizing, and overall vehicle packaging.

Simulation and analysis were conducted through key stages:

Cycle Definition: A representative duty cycle replicating the full range capability of the diesel Defender was established as the baseline.

Cost and Performance Modeling: Hybrid configurations were simulated to evaluate total cost of ownership (TCO) and life cycle efficiency, including the influence of grid charging on cost and emissions.

Mass and Volume Evaluation: Comparative analyses were performed to assess component mass and system volume between the legacy diesel and hybridized versions.

Outcome

The study determined that a hybrid configuration utilizing 15% of the BEV battery capacity (25 kWh) could achieve nearly equivalent range to the legacy diesel version, with only a minor volume increase of approximately 6 liters.

While plug-in functionality was not required, enabling grid charging could improve total cost of ownership by 1.5% to 7.3%, depending on operational usage patterns.

The results confirm that limited battery hybridization provides a cost-effective and practical pathway to extend the service life of legacy fleets, supporting defense electrification goals without significant design disruption or loss of mission capability.

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