REDARC DPS1225 12V 25A in-vehicle DC power supplyRegulated 12V 25A DC power supply, 9–32V input

Overview

The DPS1225 is a 25A switch-mode power supply that delivers a regulated 12V output from any vehicle supply between 9V and 32V, so 12V radios, lighting, computers or fridges can run reliably in a 24V truck or at the end of a long cable in a 12V vehicle. Output is selectable at 12.0V, 13.7V or 14.5V, with 50A surge capability and over 94% efficiency. Ignition control prevents start battery drain. It is not a battery charger and should be mounted to the chassis, outside the engine bay.

• Input 9–32V from 12V or 24V vehicles
• 12V models 25A/40A, 24V models 10A/20A
• Three output voltages selectable by wire
• ±1% line and load regulation, over 94% efficiency
• Ignition-controlled to protect the start battery
• Two units can be paralleled for more current

How it works

The DPS series are switch-mode DC-DC converters for powering loads, not for charging batteries, which REDARC explicitly forbids. Their input can be above, below or equal to the output, so a DPS1225 or DPS1240 gives a stable 12V supply from a 24V truck, and a DPS2410 or DPS2420 gives 24V from a 12V vehicle. Typical loads named by REDARC include lamps, radios and communications equipment, computers, small motors, fridges, pumps and TVs, and the units generate little electrical noise.

The blue wire connects to ignition or a dedicated switch, so the output only runs with the vehicle on and cannot flatten the start battery. If voltage drop on the input cable becomes excessive, the DPS reduces its input current to protect the wiring.

Key features

The orange wire selects the output: 12.0V, 13.7V or 14.5V on the 12V models and 24.0V, 27.4V or 29.0V on the 24V models, regulated to ±1% with a ±0.12V tolerance. Rated outputs are 25A and 40A (surge 50A and 80A) for the 12V units and 10A and 20A (surge 20A and 40A) for the 24V units. All share a 150×120×37mm, 680g housing with conversion efficiency above 94% and operation from -50°C to +50°C.

Installation and compatibility

The DPS must not be installed in hot areas such as the engine bay; it performs best mounted to the vehicle chassis, which acts as an external heatsink, and output derates above 55°C. Keep the output cable to the load under 1m. REDARC specifies MIDI fuses (FK40 or FK60 kits) and at least 7.71mm² cable for 1–5m on DPS1225 and DPS2410, or 13.56mm² for DPS1240 and DPS2420.

On vehicles with an earth isolation switch, the black wire must go to chassis earth, not the battery negative, so the DPS is disconnected with the vehicle. Two identical units can be connected in parallel, mounted close together on the chassis with matching wire lengths; two DPS1240s, for example, supply up to 80A.

Status indication

Three LEDs show the selected output voltage and a fourth the output status, blinking with a duty cycle that rises with current and lit solid at full power. An external LED can be wired to the green wire, which is current-limited to 6mA. Fault codes indicate internal faults, over-temperature, output or input over-voltage and reverse polarity.

Questions and answers