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elvistherv avatar image
elvistherv asked

Advice: Add additional solar on Cargo Trailer to existing RV system

So I've got an American Diesel Pusher RV with Quattro, CCGX, BV 512 860Ah of LA batteries (12v), the RV currently has solar (8 panels I think) with a third party MPPT charge controller (80A) and an Onan Genny.
The CCGX is connected to a local WiFI network that is internet-connected.


Ultimately I plan to get licensed to tow behind the RV then get an enclosed trailer to tow my pickup behind the RV.

The RV roof is already pretty full so I was thinking that I would have space on the roof of the trailer to add panels, my question is: What is the best way to add these to the system?

a) Run wires from the panels to the RV charge controller?

b) Add another MPPT controller to the trailer and 12v wires to the battery bank?

c) Add a 240v inverter and wire to the Quatrro somehow?


Option c) sounds like the most interesting but what inverter and how do I wire it in?


(Of course, I'd really like to have all of this tied into the rest of the eco-system CCGX, etc.)

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Justin Cook avatar image
Justin Cook answered ·

@ElvisTheRV, a lot of answers depend on variables that you didn't provide, such as the actual specs for the panels you have on top of the RV and that sort of thing. Let's assume for the moment, however, that adding more panels to your existing controller very possibly isn't going to do you any good because it's very possibly already about maxed-out as far as the wattage it can handle.

Having made that assumption, then, the simplest solution for you would be to install another SCC in the coach, parallel-connected to your existing battery bank, and run wires from your (theoretical) new PV panels on top of your trailer to the new SCC in your coach.

The reason you'll want the new SCC in your coach and the panels on the trailer running to it rather than the SCC on the trailer is that the cabling from SCC to battery needs to be heavier-gauge than PV panels to SCC, since the wires between PV and SCC are carrying high-voltage low-amperage current whereas the SCC to battery cables are carrying low-voltage high-amperage current. Thus you want to keep the SCC to battery cabling as short as possible.

I'm not sure what you're thinking about when you're musing "add a 240v inverter and wire it to the Quattro somehow" because the Quattro is already an inverter... and an inverter has nothing to do with your solar panels, so what's your line of thinking there?

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elvistherv avatar image elvistherv commented ·

Regarding the specs on the panels I am also a little unsure of that, I thought as much re: placement of SCC due to the voltages involved, is another option to swap out the existing SCC for a larger one rather than running 2?


My thinking on the PV inverter was based upon the use of Fronius PV inverters, which many Victron systems (including quattros) use, from the trailer panels but (as is clear) I'm a little hazy about how they would work with the quattro.

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Justin Cook avatar image Justin Cook ♦♦ elvistherv commented ·

@ElvisTheRV ahaaaa I see. I don't work with the Fronius systems personally because they're generally grid-tie (as in, designed to sell back to the grid) and that's effectively not legal here in CA (it is, but only with extremely specialized equipment) so I actually have no idea how that might work... will defer to someone over the pond from me with more experience in that.

As for swapping out your existing SCC for a larger one (assuming that yours can't handle more, which to be fair it might be able to), that would be an acceptable solution... I often recommend multiple small controllers rather than a single big controller, however, for a couple of reasons:

1 - Cost: It's usually cheaper to acquire two smaller-capacity controllers than one large-capacity;

2 - Efficiency: In many, many situations I find that you'll achieve higher charge efficiency by using multiple smaller controllers with your PV array separated into clusters. This way you could theoretically park your RV in the shade to help stay cool but leave your trailer out in the sun and the controller for your trailer panels would still be cranking away even while you took advantage of the shading on your RV. If you ran all the panels off one big controller and you tried that, your charge efficiency as a whole would drop off dramatically.

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Tom avatar image
Tom answered ·

Possibly your PV on the trailer will be different sized and powered on the trailer. With this in mind you should add a second Mppt charger near your main house battery bank and add a second charging connection to the battery. Run your PV DC cable to the back if your RV and use an Andersen battery connector sized for your amperage.

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