REDARC BCDC1240D BCDC Classic40 dual input DC-DC charger12V 40A in-vehicle DC-DC charger with MPPT solar input

Overview

The BCDC1240D, or BCDC Classic40, delivers 40A and 600W to a 12V auxiliary battery from a 12V or 24V vehicle input and an unregulated solar input that can be used simultaneously. REDARC positions it for lead-acid banks over 200Ah and lithium batteries over 100Ah, provided the battery accepts 40A. It charges in three stages with profiles A, B, C or Li, supports variable-voltage and idle-stop alternators, and is housed in the same sealed 165×120×37mm, 1kg body as the 25A model. Fuse with an FK60 kit.

• 25A, 40A or 50A output to a 12V auxiliary battery
• Vehicle and solar inputs 9–32V, used simultaneously
• Solar first, topped up from the alternator
• Profiles A, B, C for lead-acid and Li for LiFePO4
• Works with standard, variable-voltage and idle-stop alternators
• Sealed, fan-free, suitable for engine bay mounting

How it works

The BCDC Classic chargers take power from a 12V or 24V start battery and from an unregulated 12V solar array, and deliver a battery-specific charge to a 12V auxiliary battery. Because the converter can step up or down, the auxiliary battery receives the correct voltage even when a long cable run lowers the input. The charger also acts as an isolator: it starts when the engine is charging and stops when the start battery falls, so the start battery is not drained.

With REDARC's Green Power Priority the unit takes as much as it can from solar first and adds alternator power only up to its rated output. BCDC1225D and BCDC1240D charge in three stages (boost, absorption, float); the BCDC1250D adds a soft-start stage that ramps current from zero over about 30 seconds. Absorption ends when current falls below 4A for 30 seconds, and float holds 13.3V (13.6V on the Li profile).

Key features

Four charge profiles are selected with the orange wire: A (14.6V), B (15.0V), C (15.3V) for lead-acid, calcium, gel and AGM batteries, and Li (14.5V) for LiFePO4 batteries with their own BMS. The blue wire selects the standard input trigger (on at 12.9V, off at 12.7V) or the low-voltage trigger for variable-voltage and idle-stop alternators, connected to D+ or ignition (on at 12.0V). All three share a 165×120×37mm, 1kg potted housing with RCM, E-mark, CE and UKCA marks.

Installation and compatibility

Mount the charger as close as possible to the auxiliary battery, keeping that cable under 1m, in the cabin, on a chassis rail or in the engine bay away from hot spots. Output derates above 55°C and stops at 80°C, and the heatsink can reach about 60°C. Use MIDI bolt-down fuses: FK40 for the BCDC1225D and FK60 for the 40A and 50A models. For runs of 1–5m REDARC specifies at least 7.71mm² cable for the 25A model and 13.56mm² for the 40A and 50A models.

Solar panels must be unregulated 12V panels wired in parallel, never in series; the input accepts up to 32V, so most house panels are not suitable. The unit limits solar power automatically to 375W, 600W or 750W. In engine bay installations REDARC advises profile A or B, and the Li profile is not recommended there.

Status and protection

Seven front LEDs show the selected profile, which inputs are in use and the charge stage, and an optional external 12V LED can repeat the status on the dashboard. All LEDs flash a numbered code for internal faults, under- or over-temperature, high output battery voltage and input under- or over-voltage. Every 100 seconds the charger briefly pauses to measure the true start battery voltage and check that an output battery is still present.

Questions and answers