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Redarc In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 40 Amp

Redarc In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 40 Amp

Item # 331-BCDC1240D
Our Price: $508.00
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Battery Charger
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331-BCDC1240D - Solar Panels to Auxiliary Battery,Vehicle Battery to Auxiliary Battery 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. 1-800-940-8924 to order Redarc battery charger part number 331-BCDC1240D or order online at Free expert support on all Redarc products. Great prices and Fastest Shipping for Redarc In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 40 Amp. Battery Charger reviews from real customers.
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Redarc Battery Charger - 331-BCDC1240D

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

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 larger battery banks rated 200 amp-hours and higher
  • 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-FK60 - 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 led acid, calcium, and Lithium ion (LiFePO4) batteries
  • Overall dimensions: 6" long x 4-3/4" wide x 1-1/2" tall
  • Battery capacity range: 200 amp-hours and greater
  • Maximum charging voltage: 15.3V
  • Output voltage: 12V DC
  • Output power: 600 watts
  • Output current rating (continuous): 40 amps
  • Input current (maximum): 40 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 40 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

BCDC1240D REDARC In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 40 Amp

Installation Details 331-BCDC1240D Installation instructions

California residents: click here

Customer Satisfaction Score:

Customer Reviews

Redarc In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 40 Amp - 331-BCDC1240D

Average Customer Rating:  4.8 out of 5 stars   (84 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.


This unit has performed as expected. My batteries are mounted inside a plywood box in the back of my van. All the connections for the Redarc are inside the box so it has a very clean install on the exterior of the box. The two DC switches in the picture allow me to disconnect the input line to the Redarc from the vehicle's electrical system and the second disconnects my Battle Born batteries from everything. I only shut off the system when I take it into the van dealership for maintenance, and that is only precautionary.

It still works great. In fact, last week I got the solar connected and it worked without a problem.
Bill A - 07/03/2021


Flawless operation. Keeps my 6 volt golf cart batteries charged on my Truck Camper. Charges 2.5 times faster than shore power or Honda generator. I installed in hot engine compartment and it works fine. Highly recommend


Great product…works as advertised
rugged construction and you can mount it anywhere
Mounted this into the battery box on my 2021 Airstream
Fabulous customer support from Redarc
Endorsed by Battleborn

Well worth the price


This is a fantastic unit. Very easy to hook to the camper batteries, using both the solar and alternator charging functionality. Used this without any issues on a 14 day trip. The instruction manual is well written and very clear.

No more worries about the state of charge of my batteries even after a long day of driving with the camper because the battery charge level will be greater than 90% when arriving at campsite despite having a refrigerator running in the camper. Will now be able to leave solar panels at home for a short 2 day camping trip.

A few times, the battery level was in the 60%-65% charge level and it was charged back to 80+% within a few hours of driving. Just be aware that getting the lead-acid batteries from 90% to 100% takes a much long time because it has to be a constant low current.

Purchasing from etrailer was an excellent experience - received it in Canada within 2 days or order.


This battery charger is awesome. Delivers 40 amps of power for my lithium batteries while driving. So far, no problems with my 125 amp alternator using this device. Used it on a two month Utah trip.

Would by this again.

Charger is still working great. No issues whatsoever. would purchase again.
Scott H - 03/04/2022


I installed a BCDC1240D (with optional fuse kit) in my Winnebago Revel (Mercedes Sprinter). The instructions are clear and I was able to figure out the wiring requirements pretty easily. I wired the Redarc with a switch to change between profile C (winter) and B (summer). The batteries are mounted below the vehicle so I probably need profile B at higher temperatures in the summer.

I have included a picture of the Redarc installed in the passenger's seat pedestal in the van. Most of the wiring in there is Mercedes and Winnebago. You should be able to identify the Redarc (bottom center), and the two fuse holders (fuses not yet install) near the blue tape.


This thing is just great. It is rock solid in construction and function. Everywhere I go now in my Arctic Fox slide in and F350, bu two 100AH LiFePo4 batteries are charging at 45 amps along the way. The fact that the Redarc is weather proof allowed me to mount it outside under the camper skirt running my 4awg battery cables along the bottom of the camper right to it.


It's been a great product for me, it's completely autonomous, I just trust that my batteries are always charged!


I have 300ah Lifepo4 batteries from Renogy..
300 watt solar.. this unit will charge via solar or vehicle.. one or the other .. whichever has more power.. I see the lights on and see it working.. the reason I like this unit is because my batteries are only being charged from one charging source. This is safer and will improve battery life.
I just wish it could have a battery and voltage meter.. I guess I need to buy a battery monitor.. This is almost the perfect device.. it needs a display for battery life and voltage.. I would love to know what it is doing.


Easy Install. Great instructions. works perfect.


Brilliant product! Charges trailer battery while you drive!

When full-timing (almost always dry camping) we frequently found it necessary to run the generator *after* arriving at a new campsite because the “charge” line on the 7 blade RV connector delivered so little power. This fixes that: It delivers a full 40 amps to our two ~100AH flooded batteries (Walmart 29DC), which will take them from 50% to 80+% charge in less than 2 hours, our usual travel time between sites, eliminating the need to run the generator completely on most days (and we don’t skimp much on electricity, using the microwave and watching movies most evenings and a forced air heater all night).

A few tips:
1) It draws 43 amps from the vehicle, so you really need the 4 awg wire to the trailer and a heavy-duty disconnect (we used a 150 amp which works well with 4 awg).

2) At full draw the vehicle battery was at 12.8 volts at idle, so it’s right at the limit: You definitely don’t want to be drawing down the starting battery. This is on a Nissan Frontier with a 130 amp alternator, meaning you also wouldn’t want to use it on a vehicle with a smaller alternator unless you’re sure you’ll always be running it above idle and/or without lights/AC/etc. on.

3) A hydraulic crimper would of course be preferred but I used a hammer crimper which worked fine. Just be sure you shrink-tube the connection since hammer crimpers can penetrate the lugs. To get full thickness into the lugs, either fold the wire in half, run the wires (8 awg from the unit, 4 awg from the line) past each other when making a butt splice, or half-fill the lug with strands cut from your 4 awg wire and then push the line in around them. I connected it to the lugs on our inverter since there were already 4 awg lines running from that to the batteries.

4) Hookup was easy, running a 4 awg line from the truck battery to the bed not so much. I fused it of course, but it’s definitely not something you want to chafe or real drama could ensue. The maximum usable distance from the vehicle to the unit is much longer than what the manual says (e.g., if your batteries are in the back of your trailer), but you must ensure that it’s at least 4 awg all the way. Using vehicle and trailer chassis grounds are fine: You don’t need to run a negative line except for a short one between the truck and trailer frames (i.e., don’t use the hitch as a ground connection).

5) Be sure you disconnect the charging line on the trailer plug. The manual doesn’t mention this, but if you don’t you’ll lose charging capacity because some of your power will feed back through that wire.

6) I used the 15V setting to maximize charging time efficiency. It quickly trips back to 13.6 volts once reaching that (much quicker than our equalizing multistage charger, for example) so no worries about overcharging. With the standard 14.6 volt cutoff you’re giving up significant amount of charging if you only drive a short time.

7) It’s 93% efficient (according to tech support) but does run pretty warm when at full output for a long time. It should be installed in area with ventilation and definitely not in an engine compartment.

8) Redarc tech support was awesome when I had questions about the installation.

Still working great. Sometimes after a long drive our volt meter stays above 12.6 volts full charge until the next morning, something we never saw when using a generator because we never were willing to run that long enough to get a full charge.
Scott R - 07/04/2020


Excellent product, easy install. If you want the option to charge and maintain an Auxiliary Battery from main battery or solar, this is an excellent compact unit. Installed this unit a year ago for a Four wheel camper. Maintain a charge on the road and camping off road, still working strong, no longer need to charge battery in the off season using solar switching, awesome for camping and maintain healthy battery.
Thanks to etrailer for offering Redarc products, ease online ordering, support and on time delivery, outstanding. Highly recommend doing business with etrailer and buying this product and the Bulldog connectors!

Redarc unit still performing strong from the day I installed it, no issues. Recently installed Blue tooth battery monitor, no more need to go into the camper and check my digital gauges. During off season camper is stored in the garage connected to solar keep my battery strong and healthy. Pretty awesome feedback from other etrailer customers. Etrailer provided quality products like the Redarc battery charger, still highly recommend doing business with etrailer and zredarc product.
Bill K - 04/15/2020


Money wisely spent - for this casual ca mper.

So far so good, only problem is finding auto electrician willing to research and do the install
Michael - 04/14/2022


Great product(BCDC1240D)
Chevy Silverado 1500 with a variable voltage alternator
Trailer:2006 HiLo Towlite 22 foot camper with a 3 way refrigerator ( because of the hard sided trailer lowers for towing to 5 1/2 feet tall it closes off the propane gas vent to the refrigerator so you must run the refrigerator on 12volts while towing which pulls 15 amps.
This was the answer for me to charge batteries and run the refrigerator
Installed in my travel trailer oversized custom hand made battery box which is vented for cooling of the unit and the unit is also mounted to the frame of the trailer as a heat sink
I hooked it up to my solar panel to keep my batteries topped off while camping or in storage. Because of the length of wire from my start battery to the travel trailer batteries (35 feet) I used 4 gauge wire and an Anderson 175 amp plug at my rear bumper as a disconnect .For the trigger wire to a ignition circuit on the truck I used the center pin on the 7 blade pigtail of the trailer plug since I don’t have reverse lights on the trailer
I would give it 10 stars if I could


One year later: Installed this to charge 2 - 100Ah Lithium Batteries from 160 Amp Alternator - It does a much better job than just the alternator itself - the boost speeds up charging by a x4 factor - worth every penny. Highly recommend - easy install with clear instructions.

After a year of traveling full time the Radarc has proven to be one of the best investments we made. It is so reliable. Would not hesitate to buy another if this one crapped out.
John B - 02/07/2020


Using it to charge the Sprinter van house battery from the vehicle auxiliary battery. The yellow wire for the solar input is not in use right now.


Is working great in my Silverado to keep auxiliary battery charged for the bed accessories. Just added a solar suitcase to it for charging and using electrical without engine. Thinking about installing the jump circuit just for safety


Install took a little time. You will need a hydraulic connector press and then you will have to solder connectors. I ordered connectors off of the internet


Keeps my house batteries charged on my boat while my engines are running. I hope to install solar panels someday to assist with charging when I’m not underway.


Have owned this charger for a year and has not failed me yet. It is built well and don’t foresee having any issues with it anytime soon. I’m glad I chose this brand.


We installed this product in our diy camper van conversion a year ago. Installation was not difficult. We have made a few trips in our van and the unit is working well so far.


Have not installed the Redarc in my camper yet, but really appreciated the quick turnaround on my order. Quick shipping was better than Amazon.

by: 06/16/2021

good product, good customer service and speedy shipping.



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