Best way to charge my trailer battery with current setup?

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dgarber

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This is the setup I am looking at. Sorry for my crude drawing. My question is...what is the best way to connect the trailer to the truck? Y adapter on current 6awg feed in back of truck or do I need to run another set of of cables from the truck battery to the truck bumper? Also, if I used a Y adapter, is the current 100amp fuse ok or should I install a 40amp fuse on the side feeding the trailer? Any other recommendations would be appreciated. Looking at a Redarc bcdc1225. My truck is a 2016 RAM 2500 with a 220 amp alternator.
Thanks.
Doug
 

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ben10 said:
Does your truck have a 7 prong trailer plug? If so you may have power to the plug. Just wire it up to your trailer battery
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I do have the 7 way plug. It is my understanding that it can not provide enough power to safely and efficiently charge my trailer battery.
Thanks.
 
dgarber said:
I do have the 7 way plug. It is my understanding that it can not provide enough power to safely and efficiently charge my trailer battery.
Thanks.
Click to expand...
The RV plug is designed to charge a battery while trailer is connected to tow rig. As long as you aren’t running anything in the trailer.
 
That setup should be fine with a "Y" from the current cable. Do provide a separate fuse for the trailer feed.
The Redarc chargers seem to draw whatever the rating is (usually 25 or 40A depending on the type) so provide cabling for that load, I use a 60A fuse for a BCDC1240 (40A). 40A fuse for a BCDC1225 is about right.
 
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rtexpeditions said:
That setup should be fine with a "Y" from the current cable. Do provide a separate fuse for the trailer feed.
The Redarc chargers seem to draw whatever the rating is (usually 25 or 40A depending on the type) so provide cabling for that load, I use a 60A fuse for a BCDC1240 (40A). 40A fuse for a BCDC1225 is about right.
Click to expand...


Thank you for the quick reply. Other than an anderson y adapter, what would be the best way to terminate my current feed cable and split off a feed to the trailer and portable power pack? Is there a fuse panel or bus bar that would make this clean?
Doug
 
You could use a butt joiner big enough to fit two cables. Make sure the single side is packed out with another piece of cable so that it is a good mechanical join.
 
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rtexpeditions said:
You could use a butt joiner big enough to fit two cables. Make sure the single side is packed out with another piece of cable so that it is a good mechanical join.
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Going with this, in the Semi-truck and Trailer world, we would do this a lot, for the single wire side of the butt splice we would strip off three times the amount of insulation that would be normally required, then we would fold the exposed wire strands three times to make the normal 1/4” or so needed to fit inside the butt connector.
 
dgarber said:
I do have the 7 way plug. It is my understanding that it can not provide enough power to safely and efficiently charge my trailer battery.
Thanks.
Click to expand...
Blue wire on 7pin round is 12ga. Stranded . Good for 20 ADC. if you want more you have to upsize the blue chargeline conductor from source to load and protect the conductor with the appropriate breaker /fuse. Remember always protect the conductors to illiminate a fire hazard. This will allow more flow of amperage to the battery safely. Hope this helps. Rv tech 17 yrs.
 
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I'm confused....Do you have a DC to DC Charger AND a National Luna setup? You show two drawings.

Do you have a truck starting battery, a truck aux battery and trailer batteries?

Be aware, if you simply hook both batteries top a single charger, the batteries will be feeding into each other. If they are not the exact same type, age and capacity....One will discharge the other and worse case damage the batteries.

I'm not sure, but I don't think you will get 20A of charge from a 12g wire running from the trucks battery. In my experience the #7 pin usually outputs just a couple amps at best.
 
RoyB said:
I'm confused....Do you have a DC to DC Charger AND a National Luna setup? You show two drawings.

Do you have a truck starting battery, a truck aux battery and trailer batteries?

Be aware, if you simply hook both batteries top a single charger, the batteries will be feeding into each other. If they are not the exact same type, age and capacity....One will discharge the other and worse case damage the batteries.

I'm not sure, but I don't think you will get 20A of charge from a 12g wire running from the trucks battery. In my experience the #7 pin usually outputs just a couple amps at best.
Click to expand...


The first drawing is labeled Truck, the second is labeled Trailer. I am looking to add a DC to DC charger to my new trailer. I currently have a main/starting battery in my truck. I have a connection to the bed of my truck from that battery that plugs into my National Luna Portable Power Pack, which contains a deep cycle battery. I plug a National Luna fridge into the power pack. The wire feeding this setup is 16mm2. There is a 100 amp fuse on the positive wire heading back to the bed. I would also like to charge the battery on my new trailer. I am open to the best solution. The National Luna PPP has an isolator built into it to keep it from draining the main truck battery. My understanding is that the DC to DC charger will do the same thing. I assumed that I could send another fused wire run directly back to the trailer charger to keep it charge while the truck alternator is running. Let me know if I am off. Thanks.
 
This is complicated. Two devices (National Luna and DC to DC) are both trying to use the trucks battery as a source. Not sure how the devices would interpret the batteries condition to start the charge cycle to the aux and trailer batteries.

I'd call the DC to DC manufacturer for advise.....
 
RoyB said:
This is complicated. Two devices (National Luna and DC to DC) are both trying to use the trucks battery as a source. Not sure how the devices would interpret the batteries condition to start the charge cycle to the aux and trailer batteries.

I'd call the DC to DC manufacturer for advise.....
Click to expand...


Here is a diagram from Redarc's website, the DC to DC charger manufacturer I will probably use. If you replace the BCDC1225/battery from the Vehicle pic and replace it with my National Luna PPP, it doesn't seem that complicated. I will be talking with them soon to verify my setup. Thanks again for your responses.
 

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My concern is the National Luna device is a "dumb" device. It simply looks at truck battery voltage and when that is satisfied, closes a relay and draws current from alternator to charge the aux battery.

These DC to DC charghers are "smart" devices. I believe they look at more than just battery voltage and do more than just close a relay.

Will be interesting in what you here from Redarc.

I just bought the Renogy DC to DC chartger and have the exact same situation you have...Truck battery...Aux battery in rear of truck... Trailer battery
My plan was simple Anderson connectors and physically disconnect the AUIX battery and connect to trailer or visas versa as needed.

The solar on my trailer will usually charge the trailers batteries while moving. But a series of cloudy travel days could use a charge from the truck.
 
As mentioned previously, Redarc is indeed more than just a relay closing. Redarc is very sophisticated. If you are using the Redarc for battery charging/maintenance for dual batteries in the tow rig, then great, it will work well. For the trailer, I would just use the 7-Pin for charging while driving and then solar with a controller for the trailer battery. I have been running this for years and it works very well. The trailer battery is always being treated appropriately whether it is being towed or sitting unattached.
 
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HuddExpo said:
As mentioned previously, Redarc is indeed more than just a relay closing. Redarc is very sophisticated. If you are using the Redarc for battery charging/maintenance for dual batteries in the tow rig, then great, it will work well. For the trailer, I would just use the 7-Pin for charging while driving and then solar with a controller for the trailer battery. I have been running this for years and it works very well. The trailer battery is always being treated appropriately whether it is being towed or sitting unattached.
Click to expand...
This is exactly why the 7 pin trailer plug was made and called an “RV” plug. It is intended to maintain the RV deepcycle battery while the trailer is connected to the rig. Other wise we could get away with only a 6 pin trailer connector for running trailer brakes.
 
HuddExpo said:
As mentioned previously, Redarc is indeed more than just a relay closing. Redarc is very sophisticated. If you are using the Redarc for battery charging/maintenance for dual batteries in the tow rig, then great, it will work well. For the trailer, I would just use the 7-Pin for charging while driving and then solar with a controller for the trailer battery. I have been running this for years and it works very well. The trailer battery is always being treated appropriately whether it is being towed or sitting unattached.
Click to expand...

Do you use a DC to DC charger in your tear drop or do you just connect directly to your trailer battery?
 
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