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Redarc In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 50 Amp
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Redarc In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 50 Amp

Item # 331-BCDC1250D
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331-BCDC1250D - 12V Redarc Battery Charger
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Maintain the charge on your RV's battery with this dual-input, DC-to-DC smart charger. Unit installs in your vehicle or trailer and pulls power from your solar panels before tapping into the vehicle battery. Great for boondocking and dry camping. Call 800-298-8924 to order Redarc battery charger part number 331-BCDC1250D or order online at etrailer.com. Free expert support on all Redarc products. Guaranteed Lowest Price and Fastest Shipping for Redarc In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 50 Amp. Battery Charger reviews from real customers.
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Redarc Battery Charger - 331-BCDC1250D

  • RV/Camper
  • Trailer
  • Battery Charger
  • Redarc
  • 12V
  • Solar Panels to Auxiliary Battery
  • Vehicle Battery to Auxiliary Battery
  • Charges/Maintains
  • 200Ah

Maintain the charge on your RV's battery with this dual-input, DC-to-DC smart charger. Unit installs in your vehicle or trailer and pulls power from your solar panels before tapping into the vehicle battery. Great for boondocking and dry camping.


  • DC-to-DC battery charger draws power from your vehicle to provide power to an auxiliary battery on your trailer or RV
    • Ideal for battery banks rated greater than 200 amp-hours
  • Dual-input device can pull power from 2 sources
    • Connect yellow wire to solar panels (sold separately)
    • Connect red wire to 12V or 24V start battery
  • Multi-stage charging algorithm ensures a complete charge on secondary battery without overcharging
    • Boost stage - provides a constant charge while monitoring auxiliary battery voltage
    • Absorption stage - keeps voltage stable to avoid overcharging while bringing battery up to 100-percent charge
    • Float stage - maintains charge on auxiliary battery
  • Solar power capable - solar panels sold separately
    • Charger automatically draws power from panels before tapping into vehicle battery
    • Built-in MPPT regulator ensures most efficient power transfer possible in all conditions
  • Fully sealed construction with fan-free operation ensures durable performance under harsh conditions
    • Tested to ensure operation in temperatures as high as 176 F
    • Protects sensitive electronics from water, dust, and shock
  • Fault recognition technology prevents damage to batteries from voltage spikes, overheating, and reverse polarity connection
  • Battery isolator function prevents charger from pulling power from start battery when vehicle is off
  • Multiple mounting options for convenient installation
    • Secure the unit in the cabin of the vehicle, along a chassis frame rail, in the engine compartment, or on your trailer
    • Cables, fuses (331-FK40 - sold separately), and connectors sold separately
  • Made in Australia


  • Application: 12V or 24V vehicle systems with standard or smart alternators
    • Battery types supported: AGM, gel, standard lead acid, calcium, and Lithium ion (LiFePO4) batteries
  • Overall dimensions: 6-1/2" long x 4-3/4" wide x 1-1/2" tall
  • Battery capacity range: greater than 200 amp-hours
  • Maximum charging voltage: 15.3V
  • Output voltage: 12V DC
  • Output power: 750 watts
  • Output current rating (continuous): 50 amps
  • Input current (maximum): 50 amps
  • 2-Year warranty

The Redarc BCDC dual-input battery charger allows for easy charging of a DC battery while you're on the move. Most battery chargers require that you plug into an AC outlet, but this DC-to-DC charger pulls power from your vehicle's start battery instead. The BCDC also has solar power capability so that you can keep your secondary battery charged while you're parked at a remote campsite. This means that you can go off the grid without worrying about being without power.

This charger connects directly to your battery, rather than pulling power from your vehicle via the trailer connector. This is to ensure that it's able to fully charge your auxiliary battery. A standard 7-way trailer connector is limited to 10 or 15 amps of current, which will not be able to fully restore a battery for use. But this charger can transfer up to 50 amps of current to both charge and maintain your auxiliary battery.

Solar Power Compatible with MPPT Regulator

This charger can pull power from 2 different sources. The first input accepts charge from your vehicle's battery. The second input on this dual-input unit is designed to receive power from solar panels (sold separately). The built-in maximum power point tracking (MPPT) regulator on this unit ensures that the charger will get the most power possible from your panels at any given time. An MPPT regulator is able to determine the point at which your solar panels reach their maximum output. Then the regulator can simulate that load on the panels to effectively draw the most power possible. This type of regulator is more effective than traditional ones at gathering power from solar panels and at drawing power in low-light conditions.

Built-in Green Power Priority, or primary solar selection, ensures that power is pulled from your solar panels first. The BCDC will only tap into your vehicle's battery when necessary. This will save your vehicle battery from unneeded stress. It also has a built-in battery isolator function to prevent the charger from pulling power from the start battery when the vehicle is off.

3-Stage Smart Charger

REDARC BCDC Battery Charger LED Indicators

The BCDC battery charger can be used to charge AGM, gel, standard lead acid, calcium, and Lithium ion (LiFePO4) batteries. An LED on the front panel of the unit will illuminate to show the charge profile, confirming that you've wired the charger correctly based on your auxiliary battery type. This LED will be solid while the unit is charging, and it will flash when the unit is in standby mode. Additional LEDs on this panel indicate where the charger is pulling power from, and what stage of the charging process the unit is in.

This smart charger completely and efficiently charges your auxiliary battery in 3 separate stages. This ensures that the battery reaches maximum capacity without being overcharged.

The first stage of the process, the boost stage, begins when you start up your vehicle. In this mode the charger will maintain a constant current to the auxiliary battery to quickly help it regain power.

Once the unit detects that your auxiliary battery is nearing its maximum charge, the charger will move into the absorption stage. In this stage it will slowly supply the needed current to safely reach 100-percent capacity on the auxiliary battery.

The final stage is known as the float stage. In this stage the unit monitors your auxiliary battery for drops in power and supplies the needed current to keep it fully charged. If a drop in power is detected, it will revert back to the first stage and begin the charging cycle over.

Compatible with Smart Alternators

A number of newer vehicles on the market have ECU-controlled, variable-voltage alternators designed to reduce emissions and boost performance. This type of alternator varies its voltage based on the driving conditions. When the alternator voltage is low, the system can drop below 12.7V, which would deactivate a standard isolator or battery charger. However, with the Redarc BCDC battery charger, this is not an issue. Simply connect the blue override wire to the vehicle ignition and the charger will recognize that the car battery is still receiving a charge from the alternator, even if the voltage has dropped. The charger will modify its voltage requirements so that it can continue to pull power until the start battery drops to 12V, as opposed to the standard 13.2V.

Versatile Mounting

This unit can be mounted in a variety of places to best suit your application. Use the 4 mounting tabs to secure the unit in the cabin of your vehicle, along a chassis frame rail, in the engine compartment, or on your trailer. The charger should be mounted as close as possible to the auxiliary battery being charged to prevent current loss. The farther the current has to travel, the more amperage is lost. A larger diameter wire will allow more current to flow through it, which can offset the current loss that occurs with longer lengths of wire. As a result, it is recommended that you use a heavier gauge wire to cover longer distances. The table below outlines the recommended wire size for a given length of cable:

Redarc BCDC Dual Battery Charger Wiring Guide

To ensure a low-resistance connection, you will want to use MIDI fuses (331-FK60 - sold separately) when connecting the BCDC to your batteries.

For a typical lead acid battery setup, refer to the wiring diagram (shown with fuses and optional LED and solar panel - sold separately) below:

Redarc BCDC Dual Battery Charger Standard Lead Battery Wiring Diagram

For a typical Lithium ion (LiFePO4) battery setup, refer to the wiring diagram (shown with fuses and optional LED and solar panel - sold separately) below:

Redarc BCDC Dual Battery Charger Lithium Battery Wiring Diagram

BCDC1250D BCDC1225D REDARC In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 50 Amp

Installation Details 331-BCDC1250D Installation instructions

California residents: click here

Customer Reviews

Redarc In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 50 Amp - 331-BCDC1250D

Average Customer Rating:  5.0 out of 5 stars   (2 Customer Reviews)

Maintain the charge on your RV's battery with this dual-input, DC-to-DC smart charger. Unit installs in your vehicle or trailer and pulls power from your solar panels before tapping into the vehicle battery. Great for boondocking and dry camping.

- 331-BCDC1250D

Great product, small form factor, solid construction. 901555

- 331-BCDC1250D

Great 734482


Ask the Experts about this Redarc Battery Charger

  • How To Attach the Redarc In-Vehicle BCDC Battery Charger To the Start Battery
    The Redarc In-Vehicle BCDC Battery Charger part # 331-BCDC1250D needs to be installed on the trailer, next to the service/auxiliary batteries. That said, this now means you must run a wire from the Redarc In-Vehicle BCDC Battery Charger to the start battery in your vehicle. The correct size wire to use will vary based on total length as you mentioned. I recommend you go pretty large so you don't have to worry about issues with length or voltage drop. We actually have a kit that will work...
    view full answer...
  • How To Charge Lithium Ion Batteries While Driving and Hooked Up to 110 Volt Power
    In order to charge two lithium-ion batteries while you drive you really only have one option which is to use the vehicle's alternator. In order to pull current from the vehicle's alternator and apply the correct charge profile you need a pretty sophisticated device, the Redarc In-Vehicle BCDC Battery Charger part # 331-BCDC1250D which will make sure you don't undercharge the tow vehicle's battery and overcharge the trailer's batteries or vice versa. Then, in order to charge the batteries...
    view full answer...
  • Can Redarc In-Vehicle BCDC Battery Charger # 331-BCDC1250D be Used with Lithium Batteries
    The Redarc In-Vehicle BCDC Battery Charger # 331-BCDC1250D that you referenced is compatible with Lithium batteries like what you are planning on converting to. This can also accept charge inputs from an alternator and solar panel so it will work well in that regard as well.
    view full answer...
  • Recommended Wire Gauge for Redarc 331-BCDC1250D In-Vehicle BCDC Battery Charger
    It's recommended you place the charger as close to the battery being charged as is possible. According to my contact at Redarc, if the wire length will be 3-16 feet, 6 gauge cable is recommended. If that distance is greater than that, say between 16 and 30 feet, 4 gauge cable is recommended. Per Redarc, if you stay within those guidelines, the voltage drop wouldn't be an issue. I've linked to a product demonstration video featuring the Redarc # 331-BCDC1250D charger.
    view full answer...
  • Redarc BCDC Battery not Getting Enough Charge from Car Battery to Last More than Two Days
    If you are not getting enough power from your vehicle's battery to charge your Redarc In-Vehicle Battery, part # 331-BCDC1250D, for very long, you can supplement the power going into the RV battery with a solar panel like the Go Power Solar Flex, part # 34272630. We have an extensive selection here that runs the gamut of price and wattage. I've linked to this list for you. Also, be sure to check the manual linked below for the Redarc. Page 12 has a table for cable sizing. If you do...
    view full answer...
  • Solar Input Voltage Range For Redarc In-Vehicle BCDC Battery Charger
    The Redarc In-Vehicle BCDC Battery Charger - Dual Input part # 331-BCDC1250D is only compatible with unregulated 12V nominal solar panels. You can use 2- 12 volt solar panels in series. The solar input voltage must not exceed 32V. I have attached a snip from the instructions for your reference.
    view full answer...
  • Will the Redarc In-Vehicle Battery Charger Charge the Start Battery While Trailer Is Detached
    I spoke with Redarc about the Redarc In-Vehicle BCDC Battery Charger part # 331-BCDC1250D and they informed me that the unit would not charge the start battery, only the auxiliary battery bank in the trailer. That said, the unit would not let the auxiliary battery bank pull enough power from the start battery in order to create any issues with starting the vehicle so there should be no worries here. If needed, you could also use a small solar panel just to keep the start battery topped...
    view full answer...
  • Solar Panel Open Circuit Voltage For Redarc BCDC Battery Charger
    Based on my research a 12 volt panel doesn’t put out 12 volts but it produces enough voltage to charge a 12 volt battery. It produces around 18 volts and has an open circuit voltage, without a load, of 21 volts. So without a controller, you will only be able to use 1 panel. To use more than one panel you will need a controller like the Go Power MPPT Solar Charge Controller - 40 Amp - 12V and 24V # 34280435 which works with panel combinations up to 600 watts and keep the voltage between...
    view full answer...
  • Solution For Powering An ARB Fridge While Dry Camping
    I recommend the Redarc In-Vehicle BCDC Battery Charger # 331-BCDC1250D, the main reason for this is controlled current draw. By using a BCDC, this charge current will be regulated to a specific amount. The current draw from the starting battery would be limited to 55-58amps. The BCDC should be mounted no further than 5 feet from the batteries it is charging. This ensure the output voltage is not effected by voltage drop. Some other steps to consider include changing your battery...
    view full answer...
  • Can Redarc In-Vehicle BCDC Battery Charger # 331-BCDC1250D Charge 100 AH Battery Bank
    Yes the Redarc In-Vehicle BCDC Battery Charger # 331-BCDC1250D could charge a bank of 7 100 amp-hour batteries like you have. It would be a matter of wiring up the charger to the battery bank in parallel so that the charger charges all of them.
    view full answer...
  • Choosing Between The Redarc 25 amp or 40 amp Model For A 2018 RAM Promaster 1500
    Your 180A alternator will work fine with any of their BCDC models. Whether you need a 25, 40 or 50A model will depend on the size of the battery bank you’re planning to charge. If its between 75-200Ah the # 331-BCDC1225D model will be fine but if its greater than 200Ah either the # 331-BCDC1240D or # 331-BCDC1250D will work best to replenish the battery bank faster. Yes, the BCDC can accept unlimited solar Watts/ Amps but its output is limited by the model chosen (i.e. 25, 40 or 50A). Yes,...
    view full answer...
  • How to Determine if 2017 Ford E-450 Has Smart Alternator
    Thank you for all of the information! In order for the alternator on your 2017 Ford E-450 to be a smart alternator there needs to be some type of sensor to read loads; this is typically found on the negative battery terminal. If you check out the attached photo I received from Redarc you can see an example of what that sensor would look like. I'll address your questions in order, but the ultimate answer is that the Redarc In-Vehicle BCDC Battery Charger # 331-BCDC1225D (for standard...
    view full answer...
  • Does 12-V Trailer Connector Circuit at 7-way on 2017 Ford F350 Remain Active With Vehicle Running
    Once the trailer is plugged in and the brake pedal is depressed, the 12-volt power circuit on the trailer connector will become active, and can be used for whatever purposes you wish. Keep in mind that this circuit can maintain a trailer battery, but it won't have the available grunt to charge a discharged battery. To fully charge the battery while the tow vehicle is running, you'll need a DC to DC charger like # 331-BCDC1240D for a 40 amp or # 331-BCDC1250D for a 50 amp charger. If you...
    view full answer...
  • How To Choose the Correct Redarc In-Vehicle BCDC Battery Charger for Auxiliary Battery On Vehicle
    In order to choose the correct Redarc In-Vehicle BCDC Battery Charger you'll need to know the amp hour capacity of the battery bank. This would not include the starter battery for the vehicle just the auxiliary battery, the starter battery would get more than enough charge from the vehicle's alternator. Therefore, for a single 12 volt battery you'd need part # 331-BCDC1225D which is rated for 75-200 amp hour batteries (Odyssey PC2150 = 100 Ah). The Redarc In-Vehicle BCDC Battery Charger...
    view full answer...
  • How to Pick Out Redarc DC to DC Battery Charger for 450 Amp Hour Battery Bank
    The only difference between the Redarc # 331-BCDC1240D and # 331-BCDC1250D is the maximum output rating of 40 amps and 50 amps, respectively. Both of these charging units are designed for battery banks above 200 amp-hours. The difference in output means that the 50 amp version will charge your battery from dead to 100% charge faster than the 40 amp version. Overall, I recommend the 50 amp version as it would be able to charge a dead battery faster than the 40 amp version.
    view full answer...
  • Trailer Side Wire Functions for 6- and 7-Way Connectors for a Dump Trailer
    It sounds like you have either a 6-Way or 7-Way connector. I have included a couple of pictures that show the functions of 6- and 7-Way connectors for you. Basically, the 12 volt circuit from the vehicle connector will pass through to the trailer side connector and you can attach the wire associated with that circuit directly to the positive terminal of the first battery. Keep in mind that when 2 batteries are hooked together like you have it takes longer for the second battery to get...
    view full answer...
  • Which MIDI Fuses Are Needed to Install Redarc BCDC 331-BCDC1250D DC to DC Battery Charger
    You'd need # 331-FK60 60A MIDI fuses at the positive connections to the start and auxiliary battery as mentioned on page 10 of the instructions for the Redarc # 331-BCDC1250D DC to DC battery charger (see provided link). The fuses are included with the # e56ZR installation kit you'd looked at.
    view full answer...

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Info for this part was:

Expert Research:
Mike L
Expert Research:
Jameson C
Edited by:
Lindsey S
Installed by:
Jeff D
Installed by:
Shane H
Video Edited:
Zach D
Written by:
Kristina F
Video by:
Jacob H
Updated by:
Matthew E

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