grahamhe avatar image
grahamhe asked

Accessing excess power off-grid with a SmartSolar MPPT charger (for the R&D folks)

In solar battery charger systems, the battery requires less power when nearing the end of charge, but the solar panels (or turbines) can still deliver useful power. This could be exploited for heating, cooling, pumping, lighting etc. However, most potential power consumers draw a fixed power, often more than is available, so a system will cycle or tend to draw power from the battery, depending on how it is configured. For resistive loaded (eg heating elements and led lights) a "dimming" function could be implemented to match the excess power to the load. The dimming PWM output is already available in streetlight mode.

What I am proposing is a software addition that comes into play when the battery reaches float charge. It would implement a control loop to adjust the PWM output so as to maintain the float voltage while maximising the power into the load. The SmartSolar MPPT chargers already have all the input data required to generate the control signal.

The PWM signal could drive a standard dimmer, but might also a Victron new product opportunity. For example, I have a need to direct surplus energy to an 800W 240Vac heating element in a camper-van.

offgridfeature request
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

1 Answer
jomugu avatar image
jomugu answered ·

Hi all,

I'm using diy energy excess usage system for a Fronius Primo 3.1 / Multiplus 24/3000 /4500Wp Canadian Solar / 24 V 445 Topzs TAB battery bank off-gryd system.

I can detect when the Fronius is throttled, which means energy excess, and use that excess, calculated by radiation measuring, in six different presets loads. I can switch on and off those loads (1 or 0). Also, I have developed a seventh load with 0-10 V signal control.

This method can be scalable to any size. Also, I'm working now to adapt it to DC-coupling, but AC-coupling give you some extra benefits.

The loads that I'm using right now for energy excess are two AC units, one water heater (1200Wp) and a water treatment plan.

As I manage the loads via IFTTT, adding the new ones doesn't require any wiring, just some programming.

A challenge for me is the water heater to be used with a power regulator. I tried with a phase angle regulator, and the result is that the Multiplus wave is disturbing a lot. I'll read a little more about ACThor, but we must take into account that this is off-grid, no grid powerful signal to help.

Contact me if interested.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Related Resources

The feature requests topic tag can help Victron R&D find feature suggestions for products. 

There are many factors that go into the Victron product roadmap, and feedback from end-users can help.

Victron Offgrid page