Exide Technologies (CMP Batteries) has played a key role in the power requirements of the materials handling fleet at Sainsbury’s Distribution Centre at Swan Valley, Northampton. The new DC, which opened in October 2007, is Europe’s greenest distribution centre. Virtually every aspect of the centre incorporates the latest environmentally friendly principles and technology. These include a rainwater harvesting system, a ‘solar collector’ wall and a Combined Heat & Power unit.
Derek Boghurst is Sainsbury’s Material Handling Manager – Logistics and was instrumental in selecting Exide’s power systems, which include 269 Low Maintenance Liberator Silver Vented Lead Acid Batteries with Air Agitation, 105 High Frequency Chargers, Exide’s 2100.Net Battery Management System, 2 Transfer Car systems and Exide’s water filling systems..
The truck fleet is made up of 19 RRB7Aci reach trucks, 77 LPE240 powered pallet trucks, 64 OSE 250 picking trucks, 1 C4E250 NV electric counter balance truck and 7 gas powered counter balance trucks.
Over the last 3.5 years, Derek has been instrumental in encouraging three of the leading truck manufacturers to develop trucks that can take a standard battery case for low level trucks, with higher capacities. This enables Exide’s batteries to be compatible with a range of materials handling equipment, thereby reducing the total number of batteries needed. Derek has been reducing Sainsbury’s battery to charger ratio to 1.which reduces both capital and running costs both on installation of the battery change system number of batteries / chargers required. This can now practically be achieved with a sophisticated battery management system. Derek comments, “Without a system that manages the charging and rotation of batteries, there is a sub-optimal usage of batteries; the operator tends to take the nearest battery and subsequently some batteries get much more usage than others. Lead acid batteries need to be used regularly and charged/discharged correctly.”
Vic Sayer, the Exide Senior Key Account Manager for Sainsburys explains, “Poor rotation of batteries is problematical for a number of reasons. Lead acid batteries if left too long will self-discharge and crystallisation (known as Sulphation) takes place on the battery’s plates. Sulphation affects the reaction between the negative and positive plates, which in turn impedes the generation of the electrical current. If the sulphation is so severe, it can actually inhibit the electrical function of the battery and can be virtually impossible to revive. If certain batteries do not get used much – generally those at the back of the charging room – then their efficiency and service life is severely impaired”. Vic continues, “Conversely, the batteries that get used extensively will reach the end of their service life more quickly. This is because batteries have a finite number of cycles. In practice, it also usually means that a battery is taken off charge before it has reached the end of its charge cycle. This is the worst time to remove the battery. If the battery is removed at around 80% of its charge cycle, the ‘gassing’ is just starting to take place and it is at this point that the main stirring of the electrolyte takes place and at which the strength of the electrolyte is built up to give the overall runtime.”
This prompts Derek to comment on the increasing trend of opportunity charging, “Flooded lead acid battery technology is not best suited to opportunity charging, for the reason Vic outlines. It may be appropriate for some applications, other than busy DCs, but they would tend to demand a different, no-maintenance product. Exide’s 2100.Net system monitors the charging profile of each battery and instructs the operator which battery to take next, i.e. one that has reached the end of its charge cycle. If a battery is taken that has not been fully charged, then an audible warning system is activated. I receive regular management reports from the 2100.Net system, which tell me the condition of the battery fleet and monitors our power usage. It can also indicate if there are any problems with any of the batteries and also warn us if we are likely to be under-resourced during the critical Christmas run-up.”