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High-rise battery charging saves space and manpower

01 May 2010

Co-operative Food Retail Logistics has optimised the warehouse space at its new distribution centre at Birtley, County Durham by minimising the area required for charging warehouse truck batteries. The solution was to build a three-tier battery bank - with potential to go even higher - served by a novel electrically powered changing cart, believed to be the first of its type in the EU to work without hydraulics

To promote the benefits of lean manufacturing to UK companies, the Lean Factory Group UK has set up a demonstration production cell adjacent to Bosch Rexroth’s facility in Cirencester, Gloucestershire. The Group is using the cell to host half-day seminars that both explain and demonstrate how lean manufacturing, once implemented, can help companies to streamline their operations, improve efficiency, productivity, competitive position and profitability.

Co-operative Food Retail Logistics’ (CFRL’s) new 26,500m2 distribution centre opened in Birtley, County Durham just over a year ago and is equipped to store ambient, chilled and frozen foods. From this location goods are distributed to 260 Co-operative stores throughout the North East and Scottish Borders.

The Birtley site was designed from the ground up to incorporate the latest in materials handling technology. Advanced voice picking, for example, helps the 500 distribution staff on site to fulfil over 200 deliveries a day and pick half a million cases a week. The aim is to pick down to a single item if needed. To meet the projected workloads, CFRL selected a fleet of 61 electrically powered warehouse trucks from Linde, including pallet transporters, low level order pickers and reach trucks which handle to the fifth-level top beam at 11.455m - the highest currently in any of the business’s warehouses.

From its experience at other depots, CFRL had a good understanding of its requirements for the truck battery charging system, including the elimination of manual handling and lifting and the adoption of the latest technology for battery management, charging and changing. At the same time, the company was not prepared to compromise operational flexibility by minimising the overall footprint of the charging area simply to allow more space for storage.

Over 90% of the 2,000 plus batteries used across its 19 warehouses are fully sealed Hawker Evolution units, featuring a gelled electrolyte. In addition to their maintenance-free benefits and zero spillage risk, these batteries offer valve-regulated re-combination technology, which reduces gas emissions to an absolute minimum - ideal for busy food distribution operations. Chas Shepperson, national MHE fleet manager at CFRL takes up the story.

“We started with Hawker Evolution batteries in 2001 and they’ve got better as we have. The trucks at one of our other sites are still using batteries originally supplied back then. Gelled electrolyte means there is no spillage so they are safer and there are no problems with corrosion. Reduced gassing means we don’t need special ventilation. The training required is also much simpler.”

It was decided that the best way of minimising the charge area footprint was to create a bank of multiple tiers to accommodate batteries on charge. CFRL has successfully pioneered three-level banking at recent developments in Coventry and Thurrock, and while the initial plan at Birtley was for a similar configuration, there is potential for a fourth tier to cope with future growth.

Both companies accepted that four-high could be beyond the performance of the existing Hawker Pro Series BBH bull handling equipment because its hydraulic systems were at their design limit. The only practical solution was for EnerSys to devise a new version of the BBH with fully electric capability to remove any potential restrictions. This completely new model is the first of its type delivered by EnerSys and is believed to be unique to any supplier in Europe.

Redundancy was also stipulated for the system in order to maintain continuous warehouse truck operations. The solution to this was both simple and elegant with two identical banks, each with space for 42 batteries, arranged back-to-back with their own BBH. This arrangement allows one of the systems to be taken off-line for maintenance while the other continues to supply charged batteries. Moreover, the central aisle running between the two banks gives engineers access for checking, monitoring and maintaining the chargers without entering truck operating areas, promoting safety without disrupting normal warehouse operations.

The Pro-Series BBH is a semi-automated, electrically powered change cart that runs on concealed rails alongside the row of chargers. When a change is required, the truck approaches the changing area and the driver disconnects its battery. A member of staff dedicated to the battery area then takes over and completes the change.

An extending electromagnetic retrieval device fitted to the BBH extracts the battery from the truck and onto its roller bed, finally pushing it into place for charging. The device can be raised to handle batteries on the second and third levels in the charging banks. The whole process takes just 90 seconds to change a battery and has the advantage of no manual handling.

The chargers used on site are EnerSys’ Powertech HF units, which offer an energy efficiency that is as much as 20%higher than 50Hz chargers. These automatically detect 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 power is required to charge a battery and the energy costs per charge are considerably reduced, leading to significant savings in electricity costs – as much as 30% with the Evolution battery system.

All operations are overseen by an EnerSys battery management system. ‘Intelligent’ diagnostic software in the chargers transmits data via the system’s PC to a large display screen installed in the battery changing area. The display clearly indicates the order in which batteries for each type of truck should be retrieved, ensuring that only fully charged units are taken.

This makes certain that all batteries receive the correct amount of charge before being used, and that they are systematically rotated, overcoming the potential problem of operators simply taking the nearest available battery, regardless of its true state of charge. The system also ensures that batteries are charged during lower tariff overnight periods wherever possible to generate a further cost saving.
 
The management system operates in conjunction with the remote monitoring and diagnostic Powernet service from Enersys. EnerSys managers can connect at any time to the management system from their own sites and download a variety of battery related information for analysis and subsequent reporting. Metrics available include battery status, batteries used, available current, power usage, depth of discharge, charger faults by type and recent alarms. Individual batteries can be isolated and diagnostics carried out to identify specific problems. Information is then relayed to the warehouse on-site team as a maintenance requirement alert.


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