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Old 12-10-2020, 04:25 PM   #1
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Five Months of Cerbo GX Solar Power Data

It's been about 5 months since I installed the Cerbo GX and connected the four VE MPPT controllers, BMV-712 and Multiplus to the Cerbo GX. The Cerbo CX logs data to the VRM portal in the cloud. If off grid it will upload the data after Internet access is restored. I can see this data in the trailer, my house or anywhere with network access. The touch screen connected to the Cerbo GX allows me to see or control the systems via the touch screen or via remote session.

In 5 months the system has produced 727 Kilowatt hours and my Inverter/Charger has sent 1388 kilowatts Hours of power to my house transfer switch. All but about 8 days of this has been with the trailer parked at home and hooked up to the house transfer switch.

My system inverts power for the house when the batteries are above 73% and stops inverting and just passes power back to the house when the batteries are below 70%. The trailer inverter/charge is plugged into a 30 amp circuit from the house. There is a relay under the Cerbo CG control that opens or closes the 30 amp circuit from the house. When the batteries are below 70% the circuit allows power to flow from the house. The battery charging function is set to only allow enough charging to prevent the batteries from dropping below 70% state of charge. This keeps the depth of discharge on the 700 amp hours of Battle Born LiFePO4 batteries minimal.

My solar works well until about 3PM when the neighbors trees shade the roof of the travel trailer.

I haven't been heating the trailer at all when we are not camping. The Cerbo GX is monitoring the temperature at the batteries, near the Multiplus Inverter/Charger and underneath the trailer. The batteries have not gone below 31 degrees. The outside temperature has gone as low as about 20 degrees. The Inverter/Charger creates enough of its own heat that it hasn't gone below 45 degrees.

The BMS will allow the batteries will protect themselves from charging if the battery temperature goes below 25 degrees.

I have seen a $20+ reduction in my monthly power bills since I have setup this system. I have also used the system to run the house during power outages lasting up to 11 hours. The saving on the power bill is just a bonus compared to the utility of having a lot of off grid power and being able to back up the house during power outages.
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Old 12-11-2020, 10:41 AM   #2
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Your post is interesting. Ive not considered an RV being able to transfer excess solar energy to residential use. Intriguing!
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Old 12-11-2020, 04:14 PM   #3
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The process was gradual. It started because I bought a Honda EU2200 generator to augment my trailers 805 watts of roof top solar. I only used the generator when we wanted air conditioning.

I decided it would be useful to be able to use the generator at home during power outages. I installed a 10 circuit 30 amp manual transfer switch. This covered circuits that I wanted to power during outages. This included fridges and freezer, furnace, evaporative cooler, lighting, computer network and the main Dish DVR and TV.

Over time my trailer solar increased to 1440 watts and I had additional external ports for portables. I installed a VE Multiplus 3000VA inverter/charger that could do power assist which helps the generator handle load surges such as motors starting up. This helps the EU2200 keep up with loads that it couldn't handle on its own.

Last year I was manually flipping circuits in the morning to trailer power and flipping them back at about 5 pm so the batteries would discharge overnight when the solar power stopped.

This summer I bought the Cerbo GX and also installed a 30 amp relay to controller power from the trailer external power plug to the inverter/charger. I also installed a dedicated 30 amp TV outlet for the trailer. The relay uses the generator control logic in the Cerbo GX to start and stop the relay based on battery states of charge. This allows the system to permit the house power to flow into the inverter charger at the end of the solar charging period and stop the flow of power to the inverter charger in the morning once the solar power raises the battery state of charge.

I have additional panels on the awning of my patio that feed the external solar power ports on the trailer. I currently have 300 watts of additional power in addition to the stuff on the trailer roof. I plan on adding additional portable solar panels to increase the total system to about 3000 watts.
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Old 12-27-2020, 08:59 AM   #4
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Curious what are you using to stop any back feed to the grid if/when the power goes out? Grid-tied inverter shut down with the power off.
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Old 12-28-2020, 01:23 PM   #5
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I have a ten circuit manual transfer switch. Any circuit powered by the trailer inverter/charger has no connection to grid power.

The transfer switch has a generator/off/line position for each of the 10 circuits. When a circuit is switched to generator it has it's own independent circuit breaker.There is no way for the inverter power to feed back to the grid circuit breaker panel.

This is style manual transfer switch that I am using.

https://www.homedepot.com/p/Reliance...0CRK/205793178
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Old 12-28-2020, 05:12 PM   #6
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We're still looking at RVs, but I will install my own solar. One issue I've thought about is that we'll most likely only use the trailer 3-4 month a year. So when not using all that solar goes to waste. What a great idea in putting it to work for yourself.
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Old 01-17-2021, 08:57 AM   #7
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Originally Posted by astrocamper View Post
I have a ten circuit manual transfer switch. Any circuit powered by the trailer inverter/charger has no connection to grid power.

I'm curious about that, if its a manual TS then how are you powering your house during the day with the coach? Are you going out and flipping the switch to generator in the morning then back in the evening? Thanks, Bill
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Old 01-17-2021, 11:12 AM   #8
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The Cerbo GX has two relays under software control. The one associated with generator control can be tied to battery state of charge. The generator relay control is used to open or close a 30 amp relay that I inserted in the transfer switch hot input hot leg. If the relay is closed power flows from the house 30 amp circuit to the transfer switch input. When it is open the inverter must provide all the power to the circuits flipped to the generator position at the house manual transfer switch.

I use the 2nd real on the Cerbo GX to turn a pair of 140mm fans on or off. These ventilate the air from inside the trailer through the pass through storage where the VE Multiplus 3000 is located.
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Old 01-18-2021, 10:19 AM   #9
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Cool thread. I have a pretty simple system with two Battleborns and two Victron solar controllers. Just added a SmartShunt and interfaced all three via usb to a Raspberry Pi running VRM. Pi is connected over Wifi to my in-coach router which in turn is connected to the internet via cell or if at home via my home network. I also have a Samsung Galaxy Tab 8 mounted on the wall that provides local display. Works awesome. Even emails me if the battery goes outside parameters that I set (SOC, voltage, temperature).
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Old 01-19-2021, 09:01 AM   #10
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I also have a Samsung Galaxy Tab 8 mounted on the wall that provides local display. Works awesome. Even emails me if the battery goes outside parameters that I set (SOC, voltage, temperature).

I have an old Tab 8 sitting on my desk and was thinking about eBaying it. Can you post a pic of how you mounted it? I've poked around and not seen anything to buy.
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Old 01-19-2021, 09:35 AM   #11
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I used a Ram mount that I had purchased for another project. Correction my tablet is actually a Tab A 8 but similar. Mounted it to a piece of oak and screwed that to the side of the kitchen cabinet. Still need to make a couple of trim pieces to cover the screws.

https://www.rammount.com/part/RAM-HOL-TAB12U
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Old 01-19-2021, 10:31 AM   #12
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I used a Ram mount that I had purchased for another project.

Oh My, Thanks! I have 3 RAM mounts in my RV and never thought of looking at them for a wall mount. Tunnel vision problem.. -Bill
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Old 01-19-2021, 10:47 AM   #13
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I use the 2nd real on the Cerbo GX to turn a pair of 140mm fans on or off. These ventilate the air from inside the trailer through the pass through storage where the VE Multiplus 3000 is located.

Jeff, I just hooked up two fans to a MakerHawk thermostat https://amzn.to/3nYDPcy but I am intrigued to possibly use my new Cerbo to control them. Were you able to turn them on using a temp probe that can be hooked up to the Cerbo? -Bill
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Old 01-19-2021, 12:31 PM   #14
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Relay 1 was designed to support a generator start/stop so it was easy to automate without getting into running custom python code. The SOC start/stop logic was already available as a condition to control relay 1.

Relay 2 doesn't have any built in logic. It is just a remote on/off. I turn the relay 2 off manually when going to bed because I don't want to hear any fan when I am sleeping. My 140mm fans are Noctua and are pretty quiet so I don't notice them during the day. The fans are needed when running the air conditioner off the Multiplus.

I only use the 3 temperature probes for part of the data logging. I wanted to know how close my batteries are to temperature low charging limits and how warm my Multiplus is getting. The 3rd probe shows the outside temp under the trailer.

I believe there is the possibility of creating your programs and running them on the Cerbo GX. It is definitely a bit bleeding edge. There is some info regarding it if you google Cerbo GX open source. You can also run the GX software on a Raspberry Pi 4.
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