OVERVIEW
The Powerterm L120C-D is a combined Power Supply and Battery Charger for small uninterruptible instrument supply applications where both 12Volts and 24Volts are required.

Providing both 24Volts and 12Volts in battery standby systems can be inconvenient and costly. While 12Volts is available in 24Volt battery systems by centre-tapping the two series connected 12Vdc batteries, until now this has been impractical to use because of the different charging requirements of the two batteries.

The unique PTL120C-D dual voltage charger now makes this possible by the provision of true split rail battery charging to provide balanced charging to both batteries even when light 12Volts loads are tapped from the battery pack.

When the average 12Volt load is significant compared to the 24Volt load, a separate 12Volt battery is recommended.

For either configuration, the Powerterm L120C-D is the only charger component required for the system, reducing space and cost.

Applications include RTUs, dataloggers, remote field instruments and alarm systems where the requirement exists to power both 12Volt equipment (such as radios) and 24Volt instruments.

BATTERY MANAGEMENT
During prolonged power outages, the back-up batteries will eventually discharge. If the load remains connected, the batteries can enter their deep discharge phase, which can cause irreparable damage to the batteries, and reduce their capacity and life expectancy.

The PTL120C-D incorporates a low voltage cut-out that disconnects the loads when either battery voltage falls below its low voltage threshold.

The maximum float voltage necessary to ensure full charge, but not overcharge, is temperature dependent for lead-acid batteries. If the installation is in an environment with widely fluctuating temperature, then fixed voltage chargers will either under-charge or over-charge the batteries.

The PTL120C-D is provided with external temperature compensation so that the float voltage to the batteries is held at its optimum value at all times. Use Model C0003 Temperature probe (supplied separately).

DUAL MODE CHARGING
All sealed lead acid battery manufacturers specify a maximum charging current for the correct life and safe operation of sealed lead acid batteries. This maximum charging current for a battery is based upon the Ampere-hour capacity of the battery. Many conventional switch mode power supplies do not control their maximum delivered current and can cause batteries to be charged from flat with current levels that exceed the manufacturer’s recommendation. The PTL120C-D provides dual-mode charging, with a well defined battery current limit, so that even when the batteries are discharged, the charging current will be controlled.

SYSTEM MONITORING
The PTL120C-D provides an AC OK contact output. This output can be used to detect power failures without the need for an additional mains detection relay.

BATTERY TESTING
Using the Test Input, the health of the batteries can be checked. This function can be included in programmable remote equipment for highest availability of the standby system.