Sentry Series

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  • Designed for float/standby charging applications
  • Current limited
  • Thyristor controlled
  • 12V or 24V, 3A or 5A 
    (12V/10A option on Sentry 7 / Sentry UL)
  • Open frame or wall-mounted enclosure variants
  • Auto boost and temperature compensation on Sentry 7 and UL models
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Product Overview: 

The Sentry range provides reliable float charging for vented lead acid or NiCd cells. Sentry chargers are based around an economical open-frame design, but can be supplied with a wall mounted enclosure complete with ammeter. The range is available in standard Sentry, Sentry 7 or UL1236/CSA approved versions. 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.

Auto Boost
Sentry UL series and Sentry 7 series units include an Auto boost feature. Auto boost provides a temporary increase in output voltage, equalizing the charge between cells and maximizing battery life and capacity. On Sentry UL series units, auto boost is triggered automatically when the battery falls below a preset voltage. On Sentry 7 series ‘A’ option chargers, Auto Boost can also be initiated manually by linking two ‘boost’ terminals, e.g. via 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. Temperature compensation The optimum charge voltage for lead acid and NiCd batteries varies with ambient temperature. All Sentry UL series models are fitted with on-board temperature sensing and output compensation (3mV/cell decrease for each °C increase). 

Temperature compensation
The optimum charge voltage for lead acid and NiCd batteries varies with ambient temperature. All Sentry UL series and Sentry 7 series models are fitted with on-board temperature sensing and output compensation (3mV/cell decrease for each °C increase). 

Alarm output
Sentry 7 series ‘A’ option models include a relay output for remote alarm or signalling of charge fail conditions (no or low output current), e.g. due to AC supply or fuse failure, charger fault or high battery voltage.

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.