Looking for a diagram or assistance in the following setup. Fifth Wheel RV with 1 - 200 Watt solar panel, 1 - Epoch 300amph battery. I purchased Victron Multiplus -ii 2/120, solar controller and Cerbo GX2. I was hoping to use existing battery disconnect in my RV. This is what I understand so far. Take the 50amp (remove from breaker panel) connection and wire into Victron. Take 6AWG wire installed at Victron and install into breaker panel. Remove my current converter no longer needed with this system. Replace the battery cable from the battery with 1/0 and connect into Victron. This is where my questions start. Can I take this battery cable and install to existing battery disconnect and then run from disconnect to Victron? I do not have a generator so need for a transfer switch. If I can’t do this, can I just buy a disconnect switch from Amazon (currently rated) and install next Victron? Or do I have to buy a Lynx distributor from Victron? My battery has Bluetooth, so I don’t need anything from Victron to manage this. Finally, we are not boon dockers, we are 98% of the time hooked up to shore power, this is just for preparedness and emergencies. Hope this make sense. Thank you
Here’s a schematic produced by Victron. It’s more than you need but it gives you an ideal of how everything goes together as well as where fuses and breakers go.
You can use the existing disconnect. I prefer to have the Victron components upstream of the existing disconnect. Essentially, the existing disconnect is used to isolate the trailer’s 12 volt system. I also have a battery disconnect switch that allows me to turn off the entire DC system so I can isolate the battery for maintenance. Victron makes a switch, but the switch from Blue Sea Systems is also recommended. In the schematic, at least one of the switches appears to be the one from Blue Sea.
What are you going to do about the 12 volt charge coming from the tow vehicle?
Jim thank you and I had totally forgot about the truck. Can you help me with that as well? I have some electrical experience, but it’s been a minute.
You have three options here:
- Disconnect the charge from the 7-pin altogether. If you have small loads and enough solar then you don’t need charging from the truck.
- Don’t change anything and hope that the charge profile from the truck is OK and that the LiFePO4 battery never pulls to much current. Both of these are possible but can also be naively optimistic. A depleted LiFePO4 battery can suck the ever living daylights out of an alternator. The counter argument is that the wiring, fuse and relay usually doesn’t allow much more than about 20 amps on that circuit, which is usually rated for 30 amps.
- Implement a DC-DC charger. This will provide the right charge profile while also ensuring that the LiFePO4 battery never tries to draw too much current through the 7-pin connection.
An issue that comes up with options 1 and 3 is that you still have to provide 12 volt DC power to the trailer’s emergency break away system. This power cannot be provided by the 7-pin circuit, it must come from the trailer’s battery.
I’m using option 1. I have implemented a small, isolated battery on the tongue of the trailer that is used to start the generator, run the tongue jack and power the breakaway system. Current from the 7-pin doesn’t go anywhere. The tongue battery is kept charged by my house system, not the truck. I have plenty of PV to allow for that.