question

mike-kirwin avatar image

System Monitoring and Diverting loads

Hi - forum newbie here,

I'm looking at upgrading my off grid set up and welcome comments on the proposed works.

I'm keen to take advantage of the solar generation when my battery bank is charged (see No 7 below) and am still looking for solutions. This is one of the main things I'm struggling with so if anyone can help that'd be fantastic.

Having a way to monitor the whole system would also be great. Currently no comms leads run between any of the Victron kit. Maybe there's a monitoring solution built in to the multiplusII - which I haven't found time to fully research yet. So any pointers on how these devices should be talking to each other is also gratefully received.

And the other main thing I'm struggling to find is a resistive element solution that can be wall mounted for my ballast load - which would replace my elecky convection heaters (see No 6 below).

I've included a sketch of my existing and proposed layout to help with the context. The rational behind these changes is to upgrade some of the 9 year old components, to switch from a flooded lead acid to LiFEPO4 battery bank, add heating to the small outbuilding (approx 40 sq m) as part of the renovation works, optimise how things are configured and be able to monitoring the system.

Proposed Upgrade Info

  1. Upgrade inverter to a Victron Multiplus II
  2. Upgrade battery bank to a 48v 16s 2p prismatic battery solution using 280Ah cells, add a BMS - possibly from overkillSolar, new enclosure with low temp heating solution. Batts will probably be imported from China via AliExpress or Alibaba.
  3. Install a new change over unit to create an additional route for the ballast load from the existing hydro. This would divert the ballast to heat water for under floor heating in an outbuilding that's slowly being renovated. I've an M&E engineer who'll build this for me.
  4. Install a new 250l unvented tank. Possibly something from Gledhill.
  5. Install a new pico hydro scheme that’s designed to run in our wet Welsh winters to generate hot water. Probably using an off the shelf solution like PowerSprout, AmpHydro or StreamEngine
  6. Upgrade resistive ballast elements to a wall mounted solution. Still looking and struggling to identify components that could work.
  7. Identify a solution to harness energy from the solar PV when the batts are fully charged and also have a way to monitor the entire system.

If anyone spots any errors, has suggestions or can offer any input, all comments are encouraged and welcome.

Thanks in advance

caellwydrenewablesschematic1.png

MultiPlus Quattro Inverter Chargermonitoringsystem design
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3 Answers
hummingbear avatar image
hummingbear answered ·

Diversion loads are awesome and I wish there was more built-in support for this, but I've been able to harness it with some custom solutions. I use a RaspberryPi as my VenusOS device. Then I run HomeAssistant(HA) on another RaspberryPi. HA is a rabbit-hole in itself, but the short of it is it allows me to track all the data in my solar setup (battery state, charger state, generator start/stop, AC loads...etc)

I've been able to program certain conditions to take advantage of solar when my batteries are charged. For example, I only want to run my well-pump when the following conditions are met:

  • Solar Charger is in Float
  • Sun Angle/Azimuth is above 16° (better than using time before sunset)
  • AC Loads are below 400W
  • Water Tank is below 80%
  • Current weather is Sunny

With all of these conditions met I know I can run the well pump for 30min and not draw from my battery system. The pump pulls 3000W


I'm thinking of doing something similar for heating water with an electric heater.


The possibilities are endless with HA + VenusOS. I also have a really awesome dashboard for monitoring my solar

1618499448280.png


Cheers!


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JohnC avatar image
JohnC answered ·

Hi @mike kirwin

Interesting project, and worth pursuing if you have the drive to do it. But it's quite challenging in many ways, and beyond the 'generalities' we usually deal with here. To the generalities though, to help you find a starting point..

Entertaining video there, but the rPi is the poor man's answer to Victron's flagship CerboGX. https://www.victronenergy.com/panel-systems-remote-monitoring/cerbo-gx

Lotsa ports there (numbers and types), plug'n'play (vs rPi), and a great base for developing a more complex system. Victron are into this substantially, and for you Node-Red might be worth a look at.. https://www.victronenergy.com/live/venus-os:large#status_and_where_this_development_is_going

Also, take a look at the Modifications section of this Community to see similar happenings/discussion.

I wish you well with it, and would love to hear how you progress..

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thanks John - really appreciate your feedback. As always with these types of things, there's plenty to think about.


Cost:

CerboGX = £300'ish Vs the Pi solution = £100'ish, all in delivered to the door.


Install:

CerboGX looks to be easier although the Pi solution looks like it's almost plug and play - after downloading and running a couple of files.


Functionality:

CerboGX looks like it has a lot of bells and whistles. Not sure I can make full use of these. But I guess the same can be said for the capabilities of the Pi.


Integration:

CerboGX wins on aesthetics and the fact that it's made to do this task. Whereas there's the need to fiddle with the JST 4-Pin Male Header Cables on the Pi option, which doesn't look too difficult https://youtu.be/50V50lISnC8?t=1505


Both use Victron's Venus O/S.


Seeing as I have a little time on my hands before some kind of normality returns and that the cost difference can easily be used elsewhere on this project, I'm leaning towards the Pi solution. If cost wasn't an issue and time was short, I'd go for the CerboGX in a heartbeat.

mike-kirwin avatar image
mike-kirwin answered ·

answering the monitoring part of my own thread...........

This solution comes courtesy of someone called Jason who responded to Andy on his youtube channel - "off grid Garage".

https://youtu.be/50V50lISnC8

It uses a raspberry pi which collects and uploads the Victron data on to Victron's VRM cloud based system which can then be accessed from where ever you like.

I really like the look of this solution and will be giving it a go over the next few weeks.


If anyone has any ideas about how to divert the excess generation from my solar PV..........I'm all eyes and ears. If it's a shit idea - I'm more than happy to be put off from pursuing this any further by any well reasoned arguments.


Thanks in advance

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