Since 1988, SMA has been delivering battery chargers (or DC voltage supply units) for rolling stock. More than 2,000 battery chargers are used in daily revenue service in different kinds of railway vehicles. They are available for all usual input voltages, battery types and power ranges. All devices have been optimized for low weight, setting new standards for reliability.

SMA took the first consistent steps in the development of lightweight and compact devices with the first chargers developed for the DB AG in 1988. The required electric separation was achieved with highfrequency transformers.

The power range has consistently been expanded due to the availability of continually improving power transistors, new topologies and increasingly powerful microprocessors.

Battery chargers for all usual input voltages and almost all battery systems for a power of up to 25 kW are available as standard products. Whether it is a battery charger integrated in an auxiliary power supply system or as a stand-alone unit, for the connection to an intermediate circuit or directly to a train line or catenary — SMA is always able to provide the suitable charger for any imaginable application; even multi-voltage battery chargers are available. These devices function without regrouping and have proven their reliability in daily revenue service for more than 10 years.

The battery chargers' reliability, in particular, was the reason why Alstom Transport ordered them from SMA for the TGV POS traction units in the summer of 2003. The reliable battery chargers with a nominal power of 9 kW are designed for natural cooling. Additional easy-to-replace exterior fans ensure charger function even under extreme ambient conditions.

Conclusion
SMA has a wide product range of battery chargers for almost any application on rolling stock. The wide array of options and accessories allows low-cost integration at any time. Our experience of almost 20 years and continuous further development have made it possible today for SMA to provide compact, lightweight and intelligent devices with outstanding reliability.