question

Thanks for the quick answer, Mark. Yeah, the smaller inverter is fine, I've been running those numbers for a while. It's the battery size and charge stuff that I want reassurance on.

If I can't easily split excess power out before the inverter/charger I'll probably go with 240V water heating just because switching 5A or 10A AC is so much easier.

Hello Moz,
If your solar is providing enough energy the battery level will be on 100% so the heater can function, as soon as the power from the sun is not enough the inverter will take power from your battery and the SOC begins to drop which will will switch of the heater as soon as it reaches 95% (in the example)
If the solar power is increasing again your battery will be charged to 100% and so on.
Switching of the element itself is done by a simple relay with a 24V coil, bare in mind that the contact on the BMV can switch a maximum of 1A at max 60V!

If a 3000VA inverter and a 70A charger serves your needs there is no need to invest in a larger unit.
The only thing you have to adapt is the charge current setting.
The factory setting for this unit is 52A (75% of max power)
This can be done with the VE.Configure software.

Regards, Mark

Does Victron plan to manufacture an PWM load controller (f.e. triacs for up to 3-5 kW element) to control heating elements? This will be the best way to utilize opportunity loads for off-grid and DC-coupled self consumption projects. I imagine color control GX can be the brain in this situation and send data to the load controller based on the MPPT charger's available energy, without charging and discharging the battery.

Fronius offers a solution for grid-tied inverters for self consumption projects in order to have zero feed-in.

Hi Moz,

You don´t need to buy a big battery (for its current absorption capacity) just to be able to use a big solar array. Since Victron introduced the DVCC feature in their Venus devices, you can limit the net current that flows to the battery. The system will take into account the DC consumption of the inverter, and regulate the MPPT output current so that the configured maximum charge current to the battery is not exceeded. The same limit then applies to the Multiplus/Quattro charge current in case you charge with AC power, or when both the Multi and the MPPT can charge. The battery will not receive a higher charge current than what was configured as the limit. Read here: https://www.victronenergy.com/live/ccgx:start#dvcc_-_distributed_voltage_and_current_control

We have 3 kWp solar with a 250/85 MPPT, Multi 48/3000 and just 10A charge current to the battery with DVCC, because we want to consume mainly during the day and need little battery backup capacity.

About controlling the heater, read also the discussion in the link below, especially the answer from user @valos, he uses the relay of the Multiplus based on battery voltage, on at 54V and off at 52V or load bigger than 2000W.

https://community.victronenergy.com/questions/2089/mppt-dump-load.html

Hi!

In my case I am starting to work on the same topic.

The idea is to use a RPi to retrieve data via ModbusTCP from the CCGX, and then use the RPi to control a triac which will provide power to a water heater.

I got the idea as well from the Fronius Ohmpilot, but I use a regular DC coupled Victron system.

I am still learning about the different protocols, so in the next months I will start with the tests.

Hope this helps!

Fernando

I've been working for the last years in an off-grid nergy managment. I use a AC coupling Fronius Victron. The system can manage up to 6 loads that switch on and off depending on the energy excess. The prototype is now running two AC, in summer and Winter. Now I'm planning to add a 7th load, variable one, with a TRIAC, but not sure how this load could affect to the whole instalation. My concern is if the methods (Voltage Crossover Firing or Phase Angle Firing) Will affect to the installation creating a continuos micro charge/discharge clycles to the battery, accelerating aiging. Any idea about that concern? Has anyone tested a Voltage Crossover Firing or Phase Angle Firing power regulator in an off-grid PV installation?

For all of you. I developed a system a few years ago to use the energy excess. The system has been tested with really nice results with AC-Coupled Victron Fronius, 3kVA, 4,5 KWp, 24V-445Ah flooded batteries.

This system calculates in a simple and really cheap way the PV available power and calculate the excess when the Fronius intruder is throttled.

With that system, I'm running two AC, a water treatment plant and a water heater. The system can handle up to 6 loads and also has its own App to monitor, set parameters and switch on/off the different loads.

I want to start developing a version for DC coupled systems, although for excess energy usage I would recommend Ac coupling.

I've been working on this little problem too. Got a nice solution going which determines available surplus power. One of it's design goals was to not make any demands upon the battery. Runs off a Raspberry Pi (but could be anything). This cost about $50 all up. It might fit your brief @Moz . I'm Sydney based too btw if that helps.

Here's the screen, and links to post below:

https://community.victronenergy.com/questions/157637/can-i-publish-custom-topics.html

https://community.victronenergy.com/idea/160811/hot-water-heater-opportunity-load.html

Thanks. In the end I went with the relay output on the MPPT and that worked well enough. Turned out owning a big diesel thing didn't work for me so I've since sold it. But the off grid electrical part worked well :)

Hopefully this will help other people.