Fast charging makes a world of difference on paper

The capability for fast charging was the key factor that led BA Systemes to specify STH rechargeable nickel-cadmium batteries for automated guided vehicles serving a new printing press near Paris.

The capability for fast charging, to facilitate an "opportunity charging" regime, was the key factor that persuaded BA Systemes, the industrial logistic system specialist, to specify Saft STH rechargeable nickel-cadmium batteries for the fleet of five automated guided vehicles (AGVs) serving Le Monde's new printing press at Ivry sur Seine, near Paris.

Whenever an AGV is not fetching or changing a reel of paper it is able to dock automatically with a docking station to receive a fast charge which enables it to remain in operation round the clock, seven days a week, without the need for a long charging break.

The Le Monde printing facility produces around 600,000 newspapers per day and typically the AGVs will pick up and deliver 37 reels of paper per hour, with each reel weighing around 1500kg.

The onboard batteries provide power for both traction and the lifting gear which picks up and positions the reels, as well as the onboard control systems.

In addition to fast-charging capability, the high power density provided by the Saft STH cells has enabled the size and weight of the on-board batteries to be reduced by around 75% compared with the VRLA (valve regulated lead acid batteries) commonly used in this type of application - providing an important boost in the AGV's power to weight ratio.

The lead acid batteries often specified for AGV applications can not be fast charged, and would have had to be changed over with a freshly charged battery every 8h.

This would have involved significant additional costs in spare batteries and the labour required to change them, and the AGVs would need to be taken out of service.

By using nickel-cadmium batteries combined with opportunity charging BA Systemes has been able to ensure that the Le Monde AGVs are always available when required.

A further advantage of this charging regime is that the battery's depth of discharge can be kept low, usually to around 5%.

This has a major impact on its working life which should be extended to around five to seven years.

The Saft STH cells feature sintered positive and plastic bonded negative electrodes which provide the ideal combination of high power, reliability and fast charging for electric charging applications.

Each AGV is equipped with a 48V battery system composed of STH 1200 cells configured to give a nominal capacity of 120Ah.

Saft worked within a project team comprising BA Systemes, the AGV manufacturer and the charger manufacturer to ensure the on-time delivery and success of the AGV fleet for Le Monde.

BA Systemes commented: "The rapid charging capability of the STH batteries combined with their weight and space saving design and Saft's service meant that it was the best battery solution to ensure the success of the Le Monde project".

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