Sentry Series UL Approved Battery Chargers
Sentry Series UL Approved Battery Chargers


  • Floating charging, 5A @ 12 VDC
  • Auto boost operation
  • Temperature compensation
  • Alarm relay output
  • Charge ammeter
  • High quality stainless steel case, suitable for wall mounting


The Sentry UL 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 is supplied in a wall mounted stainless steel enclosure, complete with DC ammeter indication. Each unit consists of a transformer, rectifier and control circuit. The control circuit ensures that the charger maintains a battery voltage at the pre-calibrated float level, whilst supplying any additional load current up to the specified maximum.


When used as a float charger the unit is designed to give a constant current output while battery voltage is below a "knee point". Above the knee-point, as the battery approaches its float voltage, the Sentry output current ramps down. This multi-stage charge regime gives a fast charge rate, followed by float charge without overcharging.



All Sentry UL units include an Auto boost feature. Auto boost provides a temporary increase in output voltage, equalizing the charge between calls and maximizing battery life and capacity.


Auto boost is triggered automatically when the battery falls below a preset voltage. Auto Boost can also be initiated manually by linking two 'boost' terminals, e.g. using a panel switch or momentary push button. Once the batteries have reached the boost voltage level, the charger reverts to its normal float charge mode, preventing battery over-charge and gassing.



Sentry UL includes a relay output for remote alarm or signalling of a charge fail condition (no or low output current).



Sentry UL chargers give automatic compensation of output voltage with varying temperature, ensuring optimal charging and call life. Temperature is measured by a circuit board mounted sensor, or RTC option remote sensor complete with 9.5 ft (3m) lead assembly. Output voltage decreases as ambient temperature increases at a rate of 1.66 mV per ํF per cell (3 mV per ํC per cell) - see Output Calibration section.



Wall or surface-mounting is by slots/holes in the stainless steel case. Connection to panel wiring is by spring clamp terminals through access holes in the case side.


The AC supply input is protected with a circuit-board mounted fuse. An electronic polyfuse protects the DC output against reverse polarity and short circuit faults: the polyfuse automatically resets on battery disconnection, allowing correct reconnection without manual fuse replacement.

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