Custom Power Solutions

Case Studies

Custom Battery Packs - A User Story !

Tetra or Terrestrial Trunked Radio is the international standard for digital mobile communications. This digital radio system is primarily used by the emergency services and provides the users with a unique range of communication benefits including improvements in performance and enhanced facilities.   This standard, developed by the International Standards Organization bears witness to the growing popularity of this system and its acceptance can be seen by the widespread adoption by public service organizations worldwide.   Sepura's SRP2000 Portable Radio

Sepura Limited , based in the University City of Cambridge, United Kingdom is a leader in the specification, development and application of Tetra based communication products. Indeed Sepura's position as the industry leader in Tetra terminals is founded on the unparalleled experience of its staff, its history of innovation and the considerable investment it and its predecessor companies (Simoco, Philips PMR & Pye) has made in new technologies.

Sepura's expertise in public safety radios is unsurpassed and as a long established supplier is in fact the supplier of choice to many of the emergency services. The company has the in-depth knowledge and experience to deliver the most appropriate Tetra radio solution to its customers and due to its focus on the market for public safety is especially well positioned to understand and meets its customer's needs.

Hand Held Portables:

Sepura's product range includes both vehicle mounted and hand portable products. Its products are compatible and operate on all infrastructure systems from all suppliers. Sepura claim that no other terminal supplier has a better understanding, nor track record in Tetra operability. Their products are designed to be used intuitively and are meticulously tested to meet the most stringent criteria for reliability, ease of use, performance, efficiency and security.

Sepura further claims that its relentless focus on design improvement ensures that they continue to meet the developing needs of the evolving public service market.

Indeed Sepura claims a number of industry firsts including:-

• First to produce a working Tetra portable terminal

• First to demonstrate telephone call over Tetra

• First to develop 2 nd Generation Tetra public safety hand portable

Axeon Power :

Axeon Power Limited (and its predecessor companies MPower Batteries Ltd and MPower Solutions Ltd), based in Dundee, Scotland has worked with Sepura as an active partner since mid 2000 when it was invited to propose a solution for the battery requirements of its 2 nd Generation programme - the development of the SRP2000.

From the outset, Sepura's requirement was for a standard, light weight battery for inclusion in the main stream product and for a higher capacity version suitable for use in an enhanced capacity product.

The assigned Project name was Mercury - the Roman messenger of the gods and Axeon Power's initial involvement was in the identification of the battery cells.

Working with Sepura's design engineering team, Axeon Power's development engineers led by the assigned account manager jointly developed the battery specification which included major features such as:-

• Required voltage
• Demand power
• Required aspect ratio
• Weight
• Final packaging

The Battery Cells:

One of the main constraints was not the output power requirements, but the mechanical constraints of length, width, thickness and weight.

This quickly led to the project being defined around the application of Lithium Ion prismatic (rectangular) cells. It was the electrical output requirements however which we of most interest to Sepura's hardware engineers who had the difficult task of enticing the most useful airtime from the radio.

Axeon Power's task was to determine the available cells from the widest range of cell manufacturers and to evaluate their specification for possible conformance to the final product specification.

In each case a selection of cells was made from four different cell manufacturers and recommendations were made to Sepura for possible evaluation during the prototype development stage.

The Design Specification:

Over the ensuing months from mid to late 2000 Sepura's engineers continued to evolve the detailed specification. The final specification was released in January 2001 and this specification not only included the previously mentioned cell selection, but other features such as:-

• Mechanical data
• Electrical requirements including Li-Ion protection circuitry and Gas Gauging
• Interface data
• Environmental requirements
• EMC compatibility

It also included details of the required development and product testing.

The Battery :

In a nutshell the final battery was to include two Li-Ion cell connected in series together with a printed circuit board that included the Li-Ion cell protection circuitry, a NTC for battery charge termination and a gas gauge for battery charge management and battery identification.

The battery cells and the pcb needed to be encapsulated in a two part clamshell injection mouldings which would ultimately be ultrasonically welded together. One of the injection mouldings would also include gold plated connections which would serve as the external interface to the radio and as the interconnection interface to the pcb. The final battery pack also needed to be mechanically strong in as much as it needed to withstand drops of 1.5m (5 feet) onto concrete and be capable of resisting the ingress of water to agreed international specifications.

On the electrical side, the impedance needed to be kept to a minimum and the battery had to be capable of meeting other international specifications for electrostatic discharge, electrical immunity and radio emissions.

Product Development:

Axeon Power's engineers worked alongside Sepura's engineers throughout the development and tooling process. Detailed design input was made by both parties and each stage was reviewed at regular project meetings.

At each stage Axeon Power manufactured prototypes starting with prototype components prior to the production of tooling and subsequently producing battery packs from the production tooling.

The development battery packs were tested at each stage and full testing of the complete battery was carried out prior with the final product release.

Addendum:

Sepura's portable radios including the SRP2000, SRP2000sGPS & SRP3000 continue to be widely adopted by the emergency services & MPower continues to meet Sepura's needs in a timely manner - please visit their web site for more detailed information regarding their products www.sepura.com

About Axeon Power:

Axeon Power is one of Europe 's leading independent designers and manufacturers of custom power solutions for use in the widest range of portable products.

Battery products include Nickel Cadmium, Nickel Metal Hydride and increasingly Lithium Ion and Lithium Polymer. Corresponding battery charging systems are tailored to individual customer requirements

The company employs over 100 personnel at its headquarters in Dundee , Scotland where it carries out design, development and manufacturing for many UK , European and US based design companies and Original Equipment Manufacturers (OEMs). Axeon Power is represented around the world by its own sales staff and a network of partners.

In excess of 85% of Axeon Power's production is exported.

About Sepura:

Sepura is the world's leading independent TETRA terminal supplier. It designs, develops and supplies digital (TETRA) radios for the public safety market (such as police, fire and ambulance) as well as Military, Transport and Utilities. Sepura headquartered in Cambridge, England has an international network of distributors and partners supplying customers in over 50 countries worldwide.

Sepura offers the most comprehensive and largest international range of TETRA products. Its products are available in the widest range of TETRA frequency bands and operate on ALL manufacturers infrastructures.

Manufactured by Siemens, the range includes vehicle-mounted and hand portable radios including the award winning SRP2000 and the world's first public safety hand portable offer fully integrated GPS, the SRP2000sGPS

See also Axeon Power Products