The Sentry range provides automatic, current limited and thyristor controlled charging of vented lead acid or NiCd batteries. The units may be used in a wide range of industrial charging applications, including standby engines, pumps and generators.

The charger uses an open frame construction, designed for surface mounting in an enclosed panel. Each unit consists of a transformer, rectifier and control circuit. The control circuit ensures that the charger maintains a battery voltage at the precalibrated float level, whilst supplying any additional loads current up to the specified maximum.

Sentry is designed to give a constant current output while battery voltage is below a ‘knee point’ (approx. 13V on a 12V LA). Above the knee-point, as the battery approaches its float voltage, the charger output current ramps down. This multi-stage charge regime gives an optimum combination of fast charge rate, followed by float charge without overcharging.

Electronic self-resetting fuse

An electronic poly-fuse provides protection against DC output reverse polarity and short circuit faults. The fuse automatically resets on battery disconnection, allowing correct reconnection without manual replacement of fuses.

Installation and connection

Electrical connection of the AC supply input and DC output is via spring clamp terminals. Transformer, circuit board and terminal blocks are mounted on an open chassis baseplate/heatsink, designed for surface mounting in an enclosed control panel.


  • Automatic float charging: Output 5A @ 12VDC, 3A / 5A @ 24VDC
  • Simple, economic design
  • For vented lead acid or NiCd cells
  • Open-frame design for mounting in a control panel/enclosure
  • For stationary engine, genset and standby power applications