Power for Debenhams
May 1st 2008

Debenhams specified a complete power management solution from EnerSys for the warehouse trucks at its new distribution centre in Peterborough

The installation includes Hawker batteries for a range of warehouse trucks and incorporates advanced 'call forward', monitoring, management and handling systems that are designed to maximise the performance of the fleet over busy extended shifts and help ensure a long service life for the power sources.

"We selected EnerSys after assessing a number of potential suppliers on their ability to design the solution we needed, the timescales for implementation, and previous business satisfaction as well as cost," says Jim Bezzano, central operations manager at Spectrum, the retailer's logistics provider. "We're very pleased with the complete package." Debenhams' new distribution centre was commissioned when the company identified that its existing supply chain infrastructure was no longer adequate to support the growing business. The site, which is operated by DHL Exel Supply Chain and is dedicated to flat storage items such as house wares, has a 726,000ft2 footprint but with an additional 540,000ft2 of storage on mezzanines in its three main chambers providing extensive capacity for growth.

The company specified an initial fleet of warehouse trucks including eight reach trucks, seven man-rising order pickers, 16 ride-on pallet trucks and five low-level order pickers. Batteries were selected under a separate contract. The requirement was for a solution that included batteries, charge and change facilities, handling systems, and advanced monitoring and management capabilities. The objective was to ensure optimum use of power sources over an extended contract.

Enersys supplied its high-performance Hawker Perfect Plus batteries which offer extended work cycles between charges.

Charging is achieved by Hawker Powertech high frequency chargers, which offer a high level of energy efficiency (said to be as much as 20% higher than traditional 50Hz chargers). Powertech automatically detects the battery's level of discharge and will supply only the amount of power needed – and no more – to restore full charge. This means less mains power is required to charge a battery.

The Powertech charger will automatically accommodate batteries of different capacities, and is easily programmable for different battery technologies. All batteries were supplied with Hawker's Aquamatic single point filling system for topping up.

As part of its best-practice philosophy Debenhams specified air extraction systems which vent gases produced during charging to the outside of the building. It also asked for a shower at the side of the charging area.

Project engineers from Enersys worked with Debenhams and the lift truck supplier to design, configure and install the charge and change area. The opening date was brought forward for operational reasons and Enersys supplied temporary inductive power transfer 'bus bar' rails for charging the larger lift trucks while the new system was being installed.

Debenhams was keen to ensure that its battery facilities would be expandable to meet evolving requirements. One of the early decisions was the choice between single or double tiered battery storage. A double tiered configuration, with some batteries stored on racks above the others, offered the prospect of a smaller installation but would have meant extra battery handling operations. A single tier was simpler but took more space.

"We went for the single tier option but with plenty of spare space for additional batteries," says Jim Bezzano.

The original assessment had called for 1.4 batteries per truck but Debenhams decided to take a cautious approach and specify two units for each. This additional capacity will be used to provide power for short term rental trucks brought in to cope with seasonal peaks. This will ensure the temporary trucks have the same batteries as the permanent fleet. As the fleet grows the truck-to-battery ratio should move closer to the original specification without compromising fleet performance and avoiding the need for extra batteries.

Enersys supplied its state-of-the-art management system which works in conjunction with the 'intelligent' diagnostic software in the power sources to oversee every aspect of battery use. Batteries are allocated in strict rotation which means the the one with the most charge is always used, overcoming the potential problem of operators taking the nearest available battery. Battery use is spread more evenly between units. Service life is prolonged and unexpected maintenance reduced.

The lift trucks have been configured so that a battery change is required whenever it reaches a 30% charge threshold. This leaves enough energy for a return to the charge for a replacement battery. As drivers approach the changing point an overhead display indicates which battery should be used and where it can be found. An alarm sounds if the driver tries to take the wrong one.

The battery management system provides data on the number of hours and how many times a battery has been used, charge rates, operator efficiency, and so on. In this way Debenhams can build a profile of battery use across the fleet to identify and address performance issues.

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