RV Off-Grid Battery Monitor

Battery and systems monitoring is very important to any off-grid solar system. We went with a combination of the BMV 7-12 and a homebrew Victron Color Control GC by using a Raspberry Pi and a Touch screen.

Victron BMV 702  Battery Monitor

While the Victron Multiplus and the Color Control GX can have an approximate State of Charge or SOC, for true battery monitoring you need a shunt based monitor. The BMV 702 is perfect for our needs.

There are are a few model of the 700 series monitors.

  • 700 - Shunt and monitor , VE direct port.
  • 702 - Shunt, monitor and temp or midpoint sensor
  • 712 - Same as the 702 but bluetooth.

Since we have a 24 volt battery bank, keeping an eye on the midpoint voltage was important. We use the extra sensor that the 702 provides as a mid-point sensor, this also acts as an alarm for if our bank were to get out of balance.

We use the VE Direct port to connect to our Raspberry Pi running Venus OS with a touch screen (below) se we know exactly how many amps are going in and out of our house battery bank.

Victron Color Control GX  Clone on Raspberry pi

I can't say enough good things about Victron. They support open source software and help others run their Venus OS on the Raspberry Pi. They continue to provide support for their products and even things that are not their products.

We chose the Raspberry Pi route in large part due to cost. the Color Control GX is $500 or so, which is expensive for just a monitor. However the Raspberry Pi with a touch screen is $150, and Victron supports running Venus OS on it. However that's not all you have to buy and it's not that easy. There is a video below showing how to get full functionality on the Raspberry Pi with Venus OS.

What you'll need to make it work

  • The RPi with Touch Screen
  • VE Direct to USB - if you have any VE Direct items (We have 3)
  • MK3 to USB - This connects a VE Bus devices such as the MultiPlus to the Raspberry Pi

Now for our use case, once we added up 3 VE Direct adapters and 1 MK3 USB adaptor, we had another $150 worth of expenses just to connect all the VIctron MPPT Chargers and MultiPlus inverters to the Pi.

Which leads me to a new product called the Venus GX. We don't own a Venus GX just yet, but soon I hope we will. for $300 we get everything we need in one unit (maybe we'd have to buy 1 VE Direct to USB dongle) and we'd get relays and 2 resistive tank sensors. Yes you can monitor almost all RV systems with this including Tank levels. Adding tank level sensors is possible, but not without much trouble. Those who have tried ended up going with a Venus GX, and we're leaning that way now as well.

With that said, I love being able to see at a glance how much power we're using, how much we're generating, and where it is coming from. Victron also provides free Data logging and world wide access via the VRM Console. This is arguable the best kept secret of the Victron world, you can update firmware, monitor your RV's systems, and more from anywhere. You can even share a portion of it to strangers,here is ours.

I remember using it while exploring Duluth, MN to see how much power from solar we were pulling in while parked to make sure the AC could still run while boondocked.