REDARC BCDC1220 12V 20A in-vehicle DC-DC charger12V 20A in-vehicle charger for lead-acid auxiliary batteries

Overview

The BCDC1220 is REDARC's single input 12V DC-DC charger for lead-acid auxiliary batteries in vehicles with fixed-voltage or temperature-compensating alternators. It runs from 9–32V, so it can be fed from a 12V or 24V start battery, and gives a three-stage charge with profiles of 14.6V, 15.0V or 15.4V. It is rated at 20A continuous and 300W. The sealed 450g unit can be mounted under the bonnet and also isolates the start battery.

• 12V output, 20A continuous, 300W
• Vehicle input 9–32V, from 12V or 24V systems
• Three profiles for lead-acid, calcium, gel and AGM
• Built-in start battery isolation
• Sealed, fan-free, 450g, 100×120×37mm
• Not suitable for lithium batteries; no solar input

How it works

The BCDC1220 is a three-stage DC-DC charger that takes power from the start battery and alternator and charges a separate 12V auxiliary battery with a profile chosen for its type. Its converter works with input voltages above, equal to or below the output, so it can charge from a 24V truck or compensate for voltage drop along a long cable to a canopy or camper. Because it does not link the two batteries, the auxiliary battery can be of a different lead-acid type to the start battery.

Boost charging at constant current is followed by absorption at constant voltage until current drops below 4A for 30 seconds, then a 13.3V float. The charger isolates the start battery: it turns on above 12.9V and off below 12.7V, checking the unloaded battery voltage every 100 seconds.

BCDC1220 or BCDC1220-IGN

The two versions behave almost identically. The BCDC1220 suits fixed-voltage and temperature-compensating alternators: in a 12V vehicle its blue trigger wire is joined to the red input wire or to ignition, and in a 24V vehicle it must go to ignition. The BCDC1220-IGN is meant for ECU-controlled variable-voltage or smart alternators; its blue wire always goes to ignition and its lower thresholds (on at 12.0V, off at 11.9V) let it keep charging when the alternator lowers its voltage.

Installation and compatibility

Mount the charger on a flat surface close to the auxiliary battery and away from heat, in the engine bay, cabin, canopy or trailer, with four M6 fasteners. The output cable should be no longer than 1m, with its MIDI fuse within 100mm of the auxiliary battery. REDARC recommends the FK40 fuse kit and cable of at least 3.5mm² for 1–3m, 5.7mm² for 3–5m and 10.2mm² for 5–9m runs. Output derates above 55°C.

The orange wire sets profile A (14.6V), B (15.0V) or C (15.4V); in engine bay installations REDARC advises one step lower than in the cabin. Only standard lead-acid, calcium, gel, AGM, SLI and deep-cycle 12V batteries may be charged. There is no solar input and no lithium profile: REDARC's dual input models cover those needs.

Status indication

Six LEDs on the front show the selected profile and the charge status. A blinking profile LED means standby; the status LED blinks with a duty cycle that grows with output current and stays on solid at full power. The charger switches off instantly if the input falls below 8V or rises above 32.5V, and stops if the output battery is below 4V.

Questions and answers