I am in the process of purchasing a used motorhome from the family of a recently deceased man and was the only one that knew anything about the rig. The RV has a solar system, of which I know the basics and that's about it, hoping to find someone that can answer some basic questions. In the picture, I've circled in yellow, are 4 Victron Energy MPPT 75 | 15 Charge Controllers (see top link). I've circled in red, a Victron Energy MPPT 150 | 100 Charge Controller (see bottom link). Everything appears to be connected. My question is, there are 4 panels on the roof and 4 batteries, so I understand the 4 smart controllers mounted on the wall, but why would there be a second charge controller? Which one is "in charge" (dad joke)? The website has offered no help that I could find.

MPPT 75/15 Smart Solar Charge Controller

MPPT 150/100 Smart Solar Charge Controller

I don't have much experience with solar or your particular units, but this is from the website of the big controller.

Quote:

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The VE.Can SmartSolar charger is equipped with CAN bus ports. This allows for communication with additional VE.Can SmartSolar chargers. The additional units are simply "daisy chained" to each other with a single RJ45 cable between the individual units.

When connected to each other, all individual VE.Can SmartSolar chargers, will synchronise their charge stages. They can also send their data, via a single cable, to a GX monitoring device.

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Sounds like the big boy is in "charge." Kudos for the dad joke!

Thanks, I read that too, but there is no "daisy chain" with a single RJ45, they all go to some communication device instead of to each other. Maybe the communication box is an alternate way of "daisy chaining" them together.

I sent this to my lead electrician on my staff, will post his reply when I get it.

His response:

It all has to do with the solar panel configuration and output. The 75/15 are good for 75Volts max solar input and 15 Amps output to battery probably smaller/older solar panels. The 150/100 is 150 Volts solar input and 100A output to battery. These systems are kind a modular and might have started small and the grew as needed. For what I can see all the charges are hook to a common bus not one to each battery, I would assume the whole system is controlled by the Cerbo (link below) that I believe I can see the one with the network cables going to it. I bet there is an internal display ( link below) with a system this nice that you can interface with the whole system to include the solar chargers and the mutilplus inverter\charger, etc. Victron stuff networks together to maximize the performance of the system. You can also get the Victron app and can connect to each component and look at them. But answer the battery system question all the chargers are probably needed to charge what looks to be a 400Amp hour system in a reasonable amount of time.

Hope this helps

Cerbo GX - Victron Energy
GX Touch 50 & GX Touch 70 - Victron Energy

Helps immensely, much appreciated. This thing is like looking at an engine and not knowing which is the carburetor and which is the alternator, once you kind of know what piece is what it starts to make sense.

My pleasure. My email is in my profile if you need any more help, I have 40 electricians at my disposal and they are a wealth of knowledge.