bing tracking image

Redarc In-Vehicle DC to DC Battery Charger Installation

content loading

Customers compare 331-bcdc1225d to these similar products

Products Featured in this Video

How to Install the Redarc In-Vehicle DC to DC Battery Charger

Speaker 1: Today we'll be having a look at, and showing you how to install the Redarc In-Vehicle DC to DC Battery Charger with dual inputs, part number 331-BCDC1225D. Now the main reason you're going to want a batter charger like this one installed in your trailer is that this will maintain and charge your batteries in your trailer up to 100%, making sure they are fully charged when you arrive at your destination. Unlike our traditional charging systems that we run through the 7 way connector on the front of your trailer, those only get your batteries to about 80% of their capacity. This will get you all the way there.This charger will work with 12 or 24 volt battery systems. It will provide up to 25 amps of power output to maintain the charge of your batteries. This battery charger is compatible with your standard alternators from your tow vehicle, as well as variable voltage, or what are commonly known as smart alternators as well.

This charger is a dual input battery charger. It does DC to DC charging, and the way that works is when you're hooked up to your truck, it will use the alternator to fully charge your batteries. Additionally, you can hook up a solar panel to it, to maintain the charge of your batteries, and fully charge them when the trailer is not even in motion and is sitting parked. If you have a solar panel installed, it will use that to its fullest ability before taking any additional power from your tow vehicle. If you do decide to hook this up to a solar panel, it will work with unregulated solar panels that supply between 9 and 32 volts of power output.To begin our install, we need to locate the batteries that we want to be charged while driving.

In our case, we're working on a fifth wheel trailer, and our batteries are in the front storage compartment. We'll need to locate a spot to mount our charger, where it will be able to make our connections to our batteries using our cables. We've chosen this area here against the bulkhead of our trailer. It's right behind both of our battery boxes, so it gives us easy access to the batteries to make our connections, and it will be out of the way of any cargo that is stored in this compartment.We'll start by marking our bottom location where the holes go, to secure it into place. Okay, with the bottom locations marked, we can get the charger out of the way, and we'll make 2 pilot holes there.

We'll now secure it into place using 2 self-tapping screws. We'll put 2 in the top, just to help support the weight. You will have to provide your own self-tapping screws. Now we need to find a way to get a power cable like this to our charger that we'll be able to attach to our vehicle that's doing our towing. In our case, we're going to route our cable along side this 7 way wire, that goes to our truck, and we'll have another attachment point on our truck next to the 7 way, where we can plug the power in next to it.Your application may vary from doing this on a fifth wheel, or a standard trailer, or any other type of trailer.

What we're going to do is we're going to have a pull wire that we've already routed through here, next to where our 7 way cable comes out, into our battery compartment, and we'll use that to pull our power cables through. Here we got our cable pulled through now, and we have it zip-tied to our 7 way wire, so we'll have 2 leads sticking off, one being our positive and one being our ground, and we'll have 2 separate connectors that will plug into the back of our truck.In order to make our connection to our truck that's pulling our trailer, we're going to install a wench connector here. It's a quick disconnect, and this will allow us to easily plug into our truck and unplug quickly and easily. This for 6 gauge wire, and we're using 6 gauge wire on our install here, so these are going to work great for us. We'll start by cutting off some of the insulation from our wire. Use a utility knife to do this, or you can use a pair of strippers if you have one that will work on wire this thick. Once we have it cut, we'll be able to pull it off. We'll twist our wires together nice and tight. We'll take one of our connectors, and we'll place it on the wire, making sure all the wires go inside of it. Now, we'll use a crimping tool to crimp it into place. We're using a hydraulic crimper for this. These are readily available at most hardware stores. Here's what it looks like once it's crimped. Now we'll repeat this same process for our other cable.Now we'll take our plug here with the lanyard, we'll slide it over one of our wires. It doesn't matter which one. This orange wire here is our positive wire, that will go to the positive side of our terminal. As you see, there's a positive side and a negative side. We'll take our wire with the terminal crimped on, and insert it in the back end of our connector, and we'll push until it clicks into place. You can see our terminal comes out all the way, once we have it clicked in, so now we'll do the same for the other wire. Now we can take our dust cover, place it over the end and this will protect our connector when it's not in use.Now we'll cut off the insulation from the other end of our wires that we added. On our power wire, the orange wire that we're using, we'll take one of these copper butt connectors, which you'll have to supply your own. They're readily available at most electrical supply stores, and we'll use our crimper to crimp it into place. Here's what it looks like once it's crimped down. Redarc does highly recommend that we solder and heat shrink our connections. I will go ahead and get some solder inside of there, and then I'll slide our heat shrink on over this wire right here, before we crimp it onto the other end.We have some solder inside there now, so we'll take our heat shrink, we have some available on our website, if you need it, and we'll slide it down over our wire just enough so we have access to the other end of our connector. Now the other end of our butt connector on our orange wire will go to the red wire on our charger, so we'll insert that into the butt connector, and we'll crimp it into place. Now I'll pull back and make sure it's secure. Okay, with both of our wires now crimped together, we'll slide the heat shrink over the connector, and we'll shrink it into place using a heat gun versus a lighter, because this is a source of indirect heat, and it will more evenly shrink down our heat shrink, and won't damage it.Now we'll take a 6 gauge, 3/8 of an inch diameter ring terminal, which we have available on our website as part number SWC57016, and place it over the end of our black wire. This is our ground wire, and we'll crimp that into place as well. Some heat shrink over that connector as well, and we'll shrink it into place. Okay, and now the black wire that we put the ring terminal on, we need to attach it to a chassis ground. Our chassis ground goes directly to the negative post on our battery with this wire here, so if we remove this nut and place it on there, it will be grounding not only into our battery, but our chassis ground as well, providing us a superior ground connection, so that's what we're going to do.Now we have about a 3 or 4 inch section of our 6 gauge orange wire that we're using for our power wire. We'll strip back the insulation from both ends. Okay, I'll do the same for the other end. On one end of our stripped back wire, we'll place on one of our 3/8 ring terminals, and we'll crimp it down. On the other end, we'll attach a Redarc fuse holder that we have available on our website as part number 331-FK40. We'll take one of the ring terminals from that kit, stick that on the other end, and we'll crimp that as well. We have a nice, solid crimp on both ends. Now we'll take our fuse holder, place on our 40 amp fuse, and on one end, it doesn't matter which, we'll attach the smaller diameter ring terminal that comes with the fuse holder, to one of the studs, and install one of the nuts, and tighten it down.The brown wire that comes off of our charger, we'll place on one of the small ring terminals from our fuse holder kit, and we'll crimp that into place. We'll solder this connection and heat shrink it in. Now we will attach the brown cable to the other end of our fuse holder. We can now close the cover over the holder. This end here, we need to connect to the positive terminal of one of our batteries. Our batteries are interconnected, so this will charge both of them. Now connecting this to our battery is a simple process of just removing the nut, placing it over the stud and reinstalling the nut.Now depending upon your application, you may or may not need to do this step. The black cable that comes off of our charger needs to go to a ground. In our case, we're going to attach ours to the negative terminal of the battery because there is a large diameter wire that goes to the chassis ground from there, and it will still serve the same purpose. We're going to make an extension cable, just so we have enough room to route our wire cleanly, and to make the connection. On one end we'll place one of our 3/8 of an inch diameter ring terminals, and we'll crimp it into place. The other end of our extension cable, we'll attach a 6 gauge butt connector to. Now we'll attach our extension cable that we made to the black wire off the Redarc unit. Solder and heat shrink the connections. We'll do that for the rest of our connections from this point forward.The black wire, we need to attach to a chassis ground. Our chassis ground's over here via this white wire, and it goes directly to the negative terminal of our battery, so we could also attach this to the negative terminal of our battery and we'll accomplish the same purpose, so that's what we're going to do. Remove the nut, place this on, and reinstall the nut.Okay, now we have four wires left from our charger. We have a blue one, a green one, an orange one and a large, yellow one. The large yellow one is for hooking our charger up to a solar panel, so when we're not towing our trailer behind our truck, we can also still maintain the charge in our batteries, and have them fully charged at all times, with the solar panel, which is sold separately. We are not going to be using a solar panel on this trailer, so we will cut off the exposed wire. We'll come back to that in a minute.The green wire here is for an optional charge status LED indicator, which will tell us the status of what's going on with the batteries, and how they're being charged. We're also not going to be using this, so we'll do the same thing.The orange wire here is for our charging profile selection, and the way that this works, if we connect the orange wire to a common ground, we'll have a maximum charging voltage of 15 volts. If we connect it to the red wire from our charge unit, we'll have a maximum charging voltage of 15.1 volts, and if we're going to be charging lithium ion style batteries, we can connect this orange wire to the green wire for the LED output, and this will set it to lithium mode. The last way is that we can leave this disconnected and this will have our maximum charge voltage to 14.6 volts, which is just above what the maximum output is for the alternator on our truck, so that's where we're going to have this. We're just going to leave it disconnected.This leaves us with our blue wire. This is our trigger wire. This tells the charger how to work properly. Now this only applies if your vehicle has a variable voltage alternator. The truck that we're towing this trailer with does not. It has a standard alternator, so we'll be leaving this wire disconnected.Now that we have all of our exposed wires cut off that we're not going to use, we'll place some heat shrink over them, to protect them from grounding out. That way, if we ever change our tow vehicle to one that has a variable voltage alternator, we can hook up the low voltage trigger wire. Here's what it looks like bundled up. We put some loom here, used some tape and some zip ties to secure all the wiring, and our heat shrink ends, we put inside this loom here, just to secure them up out of the way, and to make everything look nice and clean.Now we find ourselves underneath the hood of our vehicle that's doing the towing. We need to have a power cable that goes from our battery to the back of the truck to make our connection. We have our power cable, as well as our ground cable, zip tied up to the battery cable of our tow vehicle, and then we routed down through our engine bay, making sure we avoid any moving parts, and sources of heat.You can see the orange and black wires that we brought down from our engine compartment. We just follow the factory wiring harness going towards the back of the truck, securing it along the way with zip ties. At this point, the wiring harness now goes inside the frame. Here's where it comes over the frame. We're still securing it to the wiring harness. The wiring harness then goes inside the frame, along side the fuel tank. We fish-wired it along there. Once we reach the end of our fuel tank, you can see the wiring harness again. It continues tying to it, goes behind our shock mount, goes along side our spare tire. We have it zip tied to the wiring harness here, and then down to the bottom of our 7 way bracket.To begin our install, we'll need to remove some of the insulation from our wires, so we use a utility knife, just to cut away our insulation a little bit. Once we've sufficiently cut around it, we'll be able to pull the end of it off. We will do the same for the other wire. Now we'll take our connector, our terminal end, and place it on one of our wires. It doesn't matter which one. Get it all the way on there, and then we'll crimp it into place. Okay, pull back and make sure it's nice and secure, and we'll do the same for our other wire. Now we'll take our quick disconnect housing, we'll pull off the cover.On the end we have a lanyard. We'll slide that over one of our wires. It doesn't matter which one. You'll notice there's a positive sign and a negative sign. We'll attach the positive to our positive cable, which in our case is the orange one here, so it will be this one. To do that, we'll just slide the cable inside of the connector, and push. When you hear it click, you know it's secure, and the negative, we'll attach the negative, which is our black one. Okay, once it clicks in, we'll pull back on both to make sure both of our cables are locked into place, which they are. We have our cover, which we can slide over, so when it's not in use it will be protected from the elements.We need to install a fuse to protect the charger and the wiring, so in case a short we're to happen, we wouldn't risk damage to the charger or our vehicle or trailer. We'll take our wire, and we'll measure off a few inches from the end of it, and cut it. We can install the Redarc fuse kit, which is part number 331-FK40.Now we're going to cut off some insulation from all three ends of our wire. I'm just using a utility knife to do this. If you have wire strippers that are big enough to do this, that's good. I don't, so I'm just using a utility knife. Okay, now that we have it cut, we'll pull off the end, and we'll twist the wire together, nice and tight, and we'll do the same for the other two ends.Now we'll take one of our ring terminals that comes with out kit, and we'll stick it on the long end of our cable. I'll stick it down all the way, and we'll crimp it into place. We did the same for one of the other ends of our short cable. Now on the other end of our short cable, since we're using 6 gauge wire, we're going to attach a 6 gauge ring terminal, with a 3/8 of an inch diameter hole, part number SWC57016, on our website, and we'll use our same crimping tool to crimp that into place.Okay, now that our connection is soldered, we'll have a great electrical connection that's nice and solid. We'll take some heat shrink, and we'll cover up our solder joint and our cable, and we'll use a heat gun to shrink it down. We'll repeat this same process of soldering and heat shrinking all of our connections from this point forward.Now we'll take our fuse holder, remove the nuts, take a provided 40 amp fuse, place it over the studs, and we'll place our terminals over the studs and reinstall the nuts. We'll use an 8 millimeter socket to tighten our nuts. Now we'll take our cover, and we'll fold it over our connections, and it will snap closed, and lock into place. Now we'll remove this nut on our positive battery post, place our ring terminal over the stud, and we'll reinstall the nut.Now that we have our power side hooked up to the positive terminal of our battery, we'll need to make a connection with our ground wire here, to the negative side. We'll cut off some insulation. Now we'll place on one of our 3/8 ring terminals that we have available on our website. Just like we've done with all of our other connections, we'll solder and heat shrink them. We'll remove the nut from our negative battery post, we'll now place our ring terminal over the bolt and reinstall the nut. Okay, that's nice and secure.That completes our look at and showing you how to install the Redarc In-Vehicle DC to DC Battery Charger with dual inputs, part number 331-BCDC1225D.

What Y.


Want to buy but need to know where to put blue wire exact f250 super duty 2016 thank you for what you. Do for customers I think I have smart alt

Etrailer Expert

Chris R.


If your F-250 has a smart alternator, the blue wire just needs to tap into an ignition circuit wire on the truck. I'm not able to track down what color (or where exactly) this wire is on the truck, but you should be able to find it relatively easily by testing the factory wiring behind the dash or under the hood. You're just looking for a wire that only receives power when the ignition is on.

Colin M.


Does the 7 pin connector continue to provide charging to the battery in tandem with the charger? Can this loop from charger back to 7 pin create a problem?

Etrailer Expert

Jon G.


The Redarc In-Vehicle BCDC Battery Charger # 331-BCDC1225D will take the 12V power from your vehicle and boost it to give your auxiliary battery the best charge possible. If you were to loop the 12V power coming out from this charger back to the 12V power wire from your 7-Way then that would present a problem as the power going out needs to go to the auxiliary battery.

Info for this part was:

Employee Jeff D
Installed by:
Jeff D
Employee Joshua S
Video by:
Joshua S
Employee Chris R
Video Edited:
Chris R
Employee Zach D
Video Edited:
Zach D
Employee Brent H
Test Fit:
Brent H

At we provide the best information available about the products we sell. We take the quality of our information seriously so that you can get the right part the first time. Let us know if anything is missing or if you have any questions.