I have an RV trailer with all Victron system and solar.
I would like to have a solar array on my tow vehicle roof that would help charge the RV bank but also when disconnected charge a small battery onboard to run a 12v cooler.
The RV has 1300ah 12v of lithium and the truck stand alone battery would be a small single lithium battery that is much smaller. I would have a selector switch between the two circuits. Both battery banks would have the same charge profiles programmed in.
Conceptually, the wiring would look like:
Panel array → disconnect switch → MPPT PV input
MPPT battery positive wire → (fuse) → A/B switch
Switch A positive wire → (fuse) → onboard positive battery terminal
Switch B positive wire → (fuse) → anderson connector positive
MPPT battery negative wire → negative junction stud?
Negative junction stud A wire → negative onboard battery terminal
Negative junction stud B wire → anderson connector negative
Anderson connector positive → (fuse) → RV battery positive
Anderson connector negative → RV battery negative
My thought is that I could not use the Victron Smart Networking feature for the mobile setup as there is potential that the truck could be set in small battery mode but within BLE range of the RV.
Are there any settings or gotchas I need to think about that are unique from what I did on the rest of my setup?
I thought about that….. but the largest dc-dc is 50amps.
I can fit 800-900 watts on the roof, so that would reduce my ability to fully pull all amps at peak sun.
I thought about a small dc-dc off of the solar output, but I think I would need a battery always connected to the solar output for the solar system to provide power.
Maybe I am not understanding what you are up to here. I am reading your original post and realizing you want to put the solar on the tow vehicle not the trailer. Sorry I missed that point.
I think your basic concept of having a single charge controller that can charge two different battery banks is viable. Having appropriate disconnects and circuit protection will be essential. You will always want to disconnect the PV from the controller first. Then disconnect the MPPT to battery connection. Then reconnect the MPPT to the other battery. Then reconnect the PV. The other issue I see is sizing the MPPT appropriately; specifically to the smaller battery.
For example if you are using a 150/70 MPPT to support 900W on the roof this will be fine for a 1300AH bank on the trailer but may exceed the maximum charging rate of you smaller battery. You will need to confirm this.
One option would be to set up two separate MPPTs with one smaller one that can be disconnected from the trailer and reconnected to the smaller battery as stated above. This would reduce the charging amperage for the smaller battery. This may be a better method for your set up for other reasons too. It can be advantageous to have your solar array on two different controllers if the panels are not getting equal sun exposure throughout the day.
Interesting thought of splitting up the charge controllers. I am not sure if that makes it more or less simple.
70amps does not seam like that would be an issue for most of the batteries I have used. They all can handle 200amp charging.
Where my brain is at…. If my inboard rv chargers are right next to my buss bars, then the voltages detected by the charge controllers will all match closely. But, if I have 30 feet of wire between my truck chargers controller and my bus bars, what voltage drop at 70 amps should I aim for and will there be any I foreseen issues?
Maybe not but could be an advantage in other ways like I said. In some situations I would say it is the best practice to do this. The whole system will work more efficiently. Depending on how your panels are wired (series, parallel) it can prevent individual modules that have a reduced output, due to shade from a tree, ac unit or antenna from reducing the current on the whole string. This may not help you with your original question but just a thought to consider.
That would be fine. Like I said, just check your battery specs. You are correct. Most 100AH batteries can handle up to 100 amps of charging.
The voltage drop and inaccurate readings are a very pertinent issue here. The MPPT will absolutely require an accurate battery voltage to operate correctly. Don’t under size the cable from the controller to the battery, and consider using a SmartBattery sense at the battery to relay accurate voltage using the Smart Network. Or, similarly you could use a SmartShunt near the battery to do the same thing. Either way 30 ft is a long distance. It may not be viable.
I would use a suitable PV panel on the roof of the tow vehicle with a connector inside (Anderson powerpole block, 4 poles) and its own regulator. The regulator connection to the battery plus is bridged over 2 of the connector contacts so if you do not use the panel, you disconnect the plug module which turns also the regulator off.
The tow vehicle system is independent, could be coupled over the XS manually if necessary
What if I had two of these. One at the RV battery bank and one at the truck battery “bank”. I have them programmed to the same network. I put a relay on each power lead and control that using a small set of signal wires back to the tow vehicle A/B switch (needs multi poles now) so the respective SmattBattery Sense is off unless I am signaling it to be on.
I would also size my wires for the long run for a “small” voltage drop. I would have to decide what drop is acceptable for this setup.
I am considering that as well, but for the price of the XS, I could also just run an A/B switch on the PV panels and just have two separate charge controllers.
I feel like there is a way to not spend that extra $400 by switching at the MPPT power outlet between the two banks.
what if I split my panels into a couple cheaper MPPT controllers as suggested earlier.
I buy one extra smaller charge controller. The extra one is installed in the truck and the rest are in the camper with smart networking configured and ve.direct to the Cerbo.
The one in the truck is directly connected to the truck mounted battery. No special communications.
I would configure my panels using an A/B switch at the pv disconnects side of the system. So, the truck gets less solar when stand alone, but the rv gets maximum when connected.
I had a similar idea. I think it is of top priority to have the controllers near the batteries they are charging.
Similar to what you are suggesting. Have one controller that will connect to the entire array installed in the trailer. And one smaller one at the truck battery.
If you do two separate series strings on the roof you could put your suggested two way(A/B) battery switch before a parallel connection near the truck battery. This will allow just one of the two series strings to operate on the truck MPPT and when switched it will connect to a bus bar where the two strings parallel to go to the trailer. Basically you will have two separate series arrays on the roof, with a total of 4 cables. Instead of a parallel connection on the roof it will be near the truck battery. Make sense?
Keep it simple. No need to create any smart network here. Unless you are suggesting two smaller MPPTs in the trailer as well and you want the functionality of the Cerbo. In that case VE. Direct makes sense. You generally would not use the smart network and a Cerbo.
