I recently installed a Renogy 20 amp DC-DC charger, along with Solar, so here is the install.
The Renogy DC-DC charge takes battery voltage from the factory charge circuit of the tow vehicle and increases the power to what would be a max of 20 amps. Most tow vehicle charge circuits only have about 5 or 6 amps output and there are some videos and posts about the possible damage from trying to charge Lithium batteries with the wet cell batteries found in tow vehicles, or vice versa, so I decided to do the install to not only have added charge amperage to the Lithium batteries but also not damage the tow vehicle battery ( I am not totally sure that this is needed but it is what I wanted to do).
Here is the final install picture.
The input is on the lower right of the charger, out put on the lower left. The yellow wire from the switch , upper left, is the trigger wire required to turn on/off the charger. I wired this from the marker lights of the RV, from the junction box located under the pin box on a fifth wheel, to the switch and then to the charger. I did this because I always tow with the trailer lights on and if I do not want the charger on I can turn it off. Using the trailer lights as the trigger came from Guest Jim and information from his install, I just added a switch.
The input wires, lower right, are from the factory wiring that was located at the self resetting breakers located under the black plastic cover, below the fuse block that I had installed in the picture. There is a white wire with red stripe that I found was the factory charge wire, which I traced to the junction box along with the white ground wire. The junction box is where the 7 RV pigtail connects to the RV. The ouput side just goes to the battery positve, the negative goes to the shunt from the BMV-712. If you have a shunt in your system it is paramount that all negative/grounds go thru the shunt in order to get proper readings of usage and charge. It is also important to trace the wires to make sure that the correct wire is used. I have not tested this system yet as it has been winter but I feel confident that it will work. Jim has used this same system for a while and has noticed that the 7 RV plug does produce a little heat, gets warm to the touch from use, so this would probably be the max that one would want to use when using the stock wiring, I will keep an eye on this and this is another reason I added a switch. There is also a trigger input on the charger to allow the user to cut the amperage in half, that would be 10 amps so would decrease the draw on the tow vehicle wiring which I can add if needed. If it comes to cutting the amperage in half I will run a dedicated set of wires that will handle the full load.
Brian
The Renogy DC-DC charge takes battery voltage from the factory charge circuit of the tow vehicle and increases the power to what would be a max of 20 amps. Most tow vehicle charge circuits only have about 5 or 6 amps output and there are some videos and posts about the possible damage from trying to charge Lithium batteries with the wet cell batteries found in tow vehicles, or vice versa, so I decided to do the install to not only have added charge amperage to the Lithium batteries but also not damage the tow vehicle battery ( I am not totally sure that this is needed but it is what I wanted to do).
Here is the final install picture.
The input is on the lower right of the charger, out put on the lower left. The yellow wire from the switch , upper left, is the trigger wire required to turn on/off the charger. I wired this from the marker lights of the RV, from the junction box located under the pin box on a fifth wheel, to the switch and then to the charger. I did this because I always tow with the trailer lights on and if I do not want the charger on I can turn it off. Using the trailer lights as the trigger came from Guest Jim and information from his install, I just added a switch.
The input wires, lower right, are from the factory wiring that was located at the self resetting breakers located under the black plastic cover, below the fuse block that I had installed in the picture. There is a white wire with red stripe that I found was the factory charge wire, which I traced to the junction box along with the white ground wire. The junction box is where the 7 RV pigtail connects to the RV. The ouput side just goes to the battery positve, the negative goes to the shunt from the BMV-712. If you have a shunt in your system it is paramount that all negative/grounds go thru the shunt in order to get proper readings of usage and charge. It is also important to trace the wires to make sure that the correct wire is used. I have not tested this system yet as it has been winter but I feel confident that it will work. Jim has used this same system for a while and has noticed that the 7 RV plug does produce a little heat, gets warm to the touch from use, so this would probably be the max that one would want to use when using the stock wiring, I will keep an eye on this and this is another reason I added a switch. There is also a trigger input on the charger to allow the user to cut the amperage in half, that would be 10 amps so would decrease the draw on the tow vehicle wiring which I can add if needed. If it comes to cutting the amperage in half I will run a dedicated set of wires that will handle the full load.
Brian
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