Home Tests TESTED – Elmdene LPS-12-G2

TESTED – Elmdene LPS-12-G2

by Andy Clutton

The LPS-12-G2 is a BS EN 50131-6 compliant 12-volt power supply unit specifically designed to accommodate communicators from a range of suppliers. It uses a Li-ion battery pack for extended life and this Grade 2 device has a 12-hour backup period. A Grade 3 version is also available with 30-hour battery support.

Getting started

This power supply is for internal use, its plastic case has captive screws either side of the front panel that when released allow the cover to fold down. Plastic click-on hinges mean that the front cover can be carefully removed if required during installation.

Sensibly sized screw-terminals are used on all connectors. Power must be supplied on the pair of dual terminals at the bottom of the PSU board these are clearly marked “L” and “N” using a suitably rated cable from a secure supply. The secondary terminals allow for the power to be looped on to a further device if required. A plastic cover shields all mains rated components from the installer. As the unit is double insulated, it does not require an earth connection.

A range of fixing points, access holes and side knockouts are available for cabling to the outside world. An upper central fixing point provides a tamper break-off point that activates a secondary tamper switch on the rear of the pcb. This switch is in series with the top mounted switch that is activated by the top cover.

If bushes or glands are used, these should be compliant with UL94 HB for flammability resistance to match the UL90 rated enclosure.

Once mounted onto a suitable wall or in an equipment rack, the supplied Li-ion battery is positioned and held in place with a flexible bungee, the battery’s three-wire connection is then plugged into the clearly marked “BATT” socket once power has been supplied. The battery is an 8.5Ah 3.6v pack MCP101434 and is given a re-charge time to 80% of less than 24 hours.

The casing has dimensions of just 260 (W) x 201(H) x 67(D) mm with a weight of 0.9kg.


All communicator connections are made using the 10-way screw terminals at the left-hand side of the pcb. These are clearly marked from the top as pairs for + & -, GEN, EPS, APS, & TAMPER.

The test unit provided an output of 12.20v off load. With external power attached the top green AC Power LED shows that power is connected. The lower red Fault LED flashes approximately every 2.2 seconds while the battery is charging and then turns off. The red LED indicates a number of diagnostics states that are referenced in the manual. The manual can be downloaded from their website; this contains over 180 manuals in multiple languages so the search option will likely be required. While there appeared to be front panel channels to allow the LEDs to be seen, the Li-Power logo label obscures them.

The GEN connections can be used to indicate a power supply fault condition, this has a normally closed state and will go open circuit under fault conditions. The EPS connections similarly operate to identify loss of external AC power. The APS connection is for battery fault. In all three cases these outputs are fed from solid state relays that show a measured resistance of around 7 ohms in normal operation going to open-circuit during fault conditions. The tamper connection is through the two physical tamper switches so goes from less than 1-ohm to open-circuit.

Read the full test report in the March 2024 edition of PSI magazine

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