REDARC BCDC1212T BCDC Trailer 12A DC-DC charger12V input current-limited DC-DC charger for trailer batteries

Overview

The BCDC1212T, sold as BCDC Trailer, charges a 12V battery on a car, boat or utility trailer from the tow vehicle while limiting its own input to 12A, so it can be supplied through the trailer plug's auxiliary pin and existing wiring once their rating has been checked. From a 12V alternator it typically gives 11A peak boost current and from a 24V alternator 20A. Profiles A, B, C and Li cover lead-acid, calcium, gel, AGM and LiFePO4 batteries. The 850g unit can be mounted in a nose cone, chassis rail or engine bay.

• Vehicle input current limited to 12A
• Can be fed from the trailer plug's 12V auxiliary pin
• 12V or 24V tow vehicles, 9–32V input
• Charges lead-acid, calcium, gel, AGM and LiFePO4
• BCDC1212S: 40A solar input via MPPT, 600W max.
• Built-in start battery isolation

How it works

Charging a trailer battery through a towing socket is usually limited by the thin wiring and pins of the harness. The BCDC Trailer chargers solve this by capping the current they take from the vehicle at 12A, which REDARC states allows safe operation through suitably rated towing harnesses, fuses and connectors without running extra heavy cables from the start battery. The converter steps up or down, compensating for the voltage drop over the long run to the trailer.

Both chargers isolate the start battery and charge in three stages: boost, absorption and float at 13.3V (13.6V for LiFePO4). The BCDC1212T delivers typically 11A peak boost current from a 12V alternator and 20A from a 24V alternator. The BCDC1212S adds a solar input that can supply up to 40A, used first through Green Power Priority before vehicle power is added.

Key features

The BCDC1212T offers profiles A (14.6V), B (15.0V), C (15.3V) and Li (14.5V); it can be mounted in the trailer nose cone, cabin, on a chassis rail or in the engine bay. The BCDC1212S has profiles A (14.6V), B (15.0V), H for heated lithium and Li (both 14.2V), a 55A maximum output current and must not be fitted in the engine bay. Both use the 165×120×37mm BCDC housing and carry E-mark approval.

Installation and compatibility

The red input cable may go directly to the trailer plug's +12V auxiliary pin, but a qualified person must check that harness gauge, connectors and vehicle fuse are adequately rated and protect the wiring in a fault. REDARC recommends the FK23 or FK30 MIDI fuse kit on the vehicle input, a 30A output fuse on the BCDC1212T and a 60A FK60 fuse on the BCDC1212S output, each within 100mm of the battery. Keep the charger within 1m of the trailer battery.

For variable-voltage or smart alternators the blue wire selects the low-voltage mode (on at 12.0V, off at 11.9V); use it only if the trailer plug is not live with the engine off, or use the RK1260 ignition relay kit. Solar panels on the BCDC1212S must be unregulated 12V panels in parallel, below 32V open-circuit voltage.

Status and protection

Front LEDs show the profile, the active inputs and the charge stage, and an optional 12V LED with integrated resistor can be fitted. Fault codes cover internal faults, under- and over-temperature, high output voltage and input under- or over-voltage. Every 100 seconds the charger checks that the input is still valid and that the output battery is connected, protecting the start battery and wiring if the output connection is damaged.

Questions and answers