Product category:
Batteries, chargers and circuit protection
News Release from: Saft Industrial Batteries | Subject: Saft STM rechargeable Ni-Cd batteries
Edited by the Engineeringtalk Editorial
Team on 20 February 2007
Ni-Cd batteries power automated vehicles
Swisslog has switched to Saft STM rechargeable nickel-cadmium (Ni-Cd) battery modules for its new generation Telelift TransCar LTC2 AGVs (automated guided vehicles).
Swisslog has switched to Saft STM rechargeable nickel-cadmium (Ni-Cd) battery modules for its new generation Telelift TransCar LTC2 AGVs (automated guided vehicles) The fast charging and deep cycling capability of the Saft STM modules enables the TransCar AGVs to take advantage of an opportunity charging regime, ensuring the round-the-clock availability that would not be possible with lead-acid batteries
Swisslog AGVs are designed to safely, accurately and continuously transport a variety of bulk items through the hospital by automatically delivering and retrieving four-wheel carts of varying configurations and loads.
The new TransCar AGV system is based on low-profile, compact, fully symmetric bi-directional vehicles that employ virtual path, laser-contour-following guidance.
This technology requires no wall targets, embedded wires or other costly building modifications.
The Saft battery modules provide power for the TransCar traction and the guidance systems, as well as for the automatic lifting platform that raises the hospital carts off the floor - with a maximum lift capacity of 450kg.
The lead-acid batteries often specified for AGVs can not be fast charged, and in this type of application would typically have to be replaced with a freshly charged battery every eight hours.
This involves significant additional costs in spare batteries and the labour required to change them, as well as the need to take AGVs out of service.
By switching to Ni-Cd batteries capable of deep cycling, combined with opportunity charging, Swisslog is able to maximise the availability of the TransCar AGVs.
Because a hospital can rely on individual AGVs being available for at least 22 hours every day, it is able to achieve significant reductions in its total AGV fleet.
The TransCar charging system consists of a wall-mounted power supply panel connected to charge rails embedded in the floor.
Charging is carried out on an opportunity basis, per vehicle as directed by the system control centre.
A safe feedback communications link requires a vehicle to be correctly positioned on the rails before the charging power can be applied.
The battery discharge rate depends on the weight of the load carried by the AGV and the distance travelled.
To ensure maximum availability, Swisslog aims to maintain the battery system at a state of charge between 50 and 80%.
This means that when not in service, the TransCar AGVs are directed to charge as often as possible, even if only for a few minutes.
The 100A charge current will recharge around one third of the capacity of the Saft STM battery modules in under 20 minutes.
Saft STM battery modules have been developed to meet the needs of electric vehicles for energy density (for range), power (for acceleration) and low maintenance.
They feature sintered positive electrodes and plastic-bonded negative electrodes.
Each TransCar AGV is equipped with four Saft STM 5-100 modules in series to create a 24V, 100A battery system.
A typical example of the advantages of the TransCar AGVs powered by Saft batteries is provided by a large suburban hospital in North America.
Previously, the 10-floor building employed a 26-year old wire-guided AGV system that required 60-plus vehicles to deliver materials.
By switching to the TransCar system, the hospital is now able to use its AGVs to carry out even more work with a fleet of just 16 vehicles, thanks to the increased availability provided by opportunity charging.
The hospital estimates that the TransCar system will achieve payback in just over two and a half years, and offers projected savings of over Eur 8.5 million over a 15-year period. Request a free brochure from Saft Industrial Batteries ...
• Saft Industrial Batteries: contact details and other news
• Email this article to a colleague
• Register for the free Engineeringtalk email newsletter
• Engineeringtalk Home Page
Search the Pro-Talk network of sites
