As I continue to design the system for my truck camper there is something I can not find much about. That is a 12v to 24v boost converter. That way I can continue to charge while driving. Or will the 7 pin truck power running through a Victron Energy MultiPlus-II Inverter/Charger 3000VA 24V 70A work just fine? Or should I run a separate charging circuit from the battery and convert 12v to 24v ? What would the the proper amp rating be on such a boost converter and does victron make one ?
They have several models of 12V to 24V (See DC-DC under charge & convert). Your 7 pin connector truck won’t supply enough power to do much of anything useful, and it’s 12V (assuming your truck is 12V). Your Multiplus requires a decent sized 24V battery and stout enough wiring to handle 150-200A.
The converter rating and wire size depends on the current you require. If your aim is to charge your 24V batteries from your alternator, start with how much current can your alternator safely provide. For converters, the Orion XS1400 would be my choice. It’s very efficient and plays well with the Cerbo & DVCC.
The F350 alternator is rated at 195 but a higher amp version is available. Will be a dual 300ah set of batteries to start and upgrading to 3 in total at a later date. That converter seems just what I need to go from 12v alternator to 24v battery especially being it can detect when truck is running.
The XS1400 can pull up to 50A out of your alternator, the 24V output will be approximately half of that, but you can put several in parallel.
I would plan a switch to disable them manually, you never know. I wonder if you could also use the Pro Power Onboard to charge?
Beyond one, maybe two, Orions you are better off just installing a 2k or 3k MultiPlus under the back seat and run 120V into your shore power connection. I have a Multi 2k under the back seat of F-350 and a Multi-II 24/5000 in my travel trailer. You need to size the inverter in the truck to the minimum AC input current limit for your model of Multi, which is 7.5A. If you keep it cool enough, a VE.Direct 12/1200 might be able to keep up with your 3kVA Multi in the camper, but I would upgrade to at least a Multi 2k in the back of the truck.
I say this as an installer who used to install a lot of DC-DC chargers between trucks and truck campers and trucks and trailers. By the time you run all of the properly sized DC cables to handle the power at those low voltages, and to install a properly weather-tight connector system (not just open Anderson Connectors), you can instead install an inverter and have one set of large DC cables running from the rear seat to one of the starter batteries. This is much easier in the end.
P.S. You can use a smaller inverter in the tow vehicle, but you’ll want to write a Node-Red flow that presents itself as virtual switches in VenusOS to disable PowerAssist on the Multi inside the RV so you can set the input current limit lower. The downside is, any AC loads inside the RV will be limited by whatever comes in AC-In-1. Or, just install a Multi 2k in the truck and never deal with it.
OK. I went to thinking and had to start this post over from scratch. I am new to this and somethings take a little bit to grasp. So you are saying install a 2k multiplus behind the seat and power that from from the truck battery. Then out of that inverter run a connection to shore power connection on camper. Sounds like I could mount a receptacle in the truck bed and just use a short cord. I think I saw a YouTube person do this and he kept his battery bank in the truck itself. He kept it at 12V though and lost a lot of space having a 800ah reserve. I want to run at 24v and have more space for more batteries. Is there a schematic on the system you recommend that I can see? Are you running a 195amp alternator? I don’t need to run the entire camper from the truck but to help charge the battery bank when driving along with the roof solar. I like this idea. Is it better for both inverters to match ? The truck camper inverter will only be powering 120 to an AC and microwave so maybe the 3k is a bit much. Can you provide a link to the correct multi 2k you mention ? and that is 12V correct to match alternator output?
What I am suggesting is a MultiPlus like this in the back of the truck: https://www.victronenergy.com/inverters-chargers/multiplus-2000-va And then use the system you planned inside the truck camper. The one in the truck is the AC source for the one in the camper, and can be used to more quickly charge the 24V batteries in the camper. A single Orion XS 1400 will charge at about 700W maximum. If you want to pull more energy out of the alternator then you can use two Orion XS 1400 or a small MultiPlus. The decision comes down to how much space you want to use in the truck and how quickly you want to recharge batteries in the camper.