Powering the Response: How Merlin Ended Battery Failures for Dorset & Wiltshire Fire and Rescue

Client: Dorset & Wiltshire Fire and Rescue
Industry: Blue Light
Date: August 2026

Overview

In Fire and Rescue, as with all blue light applications, the need for continuous vehicle availability is absolute. Battery failure, and the delays it can lead to, can be as critical as life and death if an appliance cannot promptly respond to calls. When Dorset Fire & Rescue had a period of multiple batteries dying before there stated service life, they knew action was required to get it resolved.

Merlin first started speaking with Andy Mumford from Dorset & Wiltshire Fire and Rescue in January 2024. At the time, Dorset were experiencing frequent issues with batteries unexplainably gassing and failing, requiring immediate replacement with knock on implications in terms of vehicle availability, replacement costs and engineering time.

Project Details

Following an initial consultation with the Merlin team, an agreement was made to supply and fit 2 of Merlin’s Datacell II units to collect information directly from the appliance for further analysis of the auxiliary power system. The Datacell’s collected information over a 48 hour period of real in-service usage – providing detailed power information for further analysis. This analysis would allow an informed plan of action to then tackle the repeated failure.

The conclusion of the test revealed overcharging of the batteries was taking place as a result of the existing charger not moving from bulk to float charge mode, as result of the draw of on-vehicle load

Acting on the report findings, Dorset and Wiltshire undertook independent testing on a range of alternative chargers from across the market – including Merlin’s own 24v 30A Abso unit. We were delighted when the unit was selected by Dorset for replacements across the fleet.  

The Result

Since 2024 and the adoption of the Merlin charger, Dorset and Wiltshire have experienced a dramatic decrease in battery failures across the fleet and continue to receive reliable charging from the Merlin units to date.  

"We were seeing an unusual number of battery failures across parts of the fleet, with batteries failing well before their expected service life. Vehicle availability is critical for us, so understanding the root cause quickly was essential. The data collected by Merlin's Datacell units gave us clear visibility into what was happening within the charging system and allowed us to make an informed decision based on evidence rather than assumption. Since implementing the recommended solution, we've seen a significant reduction in battery-related issues, helping improve fleet reliability and reduce maintenance demands."

— Andy Mumford, Fleet and Equipment Engineering Manager, Dorset & Wiltshire Fire and Rescue Service