Hi,
In my off-grid home (working since 29 years, in between mostly managed with victron products) I am used to put excess energy (from 7kWp solar and 3 kWp wind energy) into hot water tanks (for central heating and hot water).
In the beginning, when I only had 800 W solar and 1kW wind max power I used a LMW 24v power regulator that put the excess power into a 1.2 kW/24V heating element in my hot water tank, and this regulator managed it to burn exactly only that power that was excessive when the batteries were full: It powered up the element stepless when the system voltage was increasing (I think using MOSFETs) above f.e. 28.2V. So the batteries were protected from bigger loads as it would be if the excess "burning" was switched by a relay: only excessive power would be burnt.
Now I put the excessive power (when the batteries are full and the voltage exceeds 27.6V) into water, and I am using the 3 relays in my Quattro for switching 3 heaters of each 1.4 kW in steps of + 0.3V. But these steps are rather raw, and on a day with many clouds or changing winds the relays are switching and switching. I could delay their reactions, but that would stress the batteries more.
So I asked Johannes Boonstra from victron if he is interested in developing such a device that regulates excessive power stepless (in the wallbox a similar solution should be implemented). but he answered that they won't build such a device.
Who helps me to design and build a DC-voltage-controlled unit for a stepless powering of a 230V-heater, f.e. up to 6 kW for using all the maximum excess power of my solar panels and the power of the Quattro? I have some ideas, but I cannot design electronic circuits - I can solder and build near everything, but developing or programming.....that is not mine!
I think first I need a voltage devider that gives me the excessive voltage out to feed an OpAmp or a microcontroller that gives out PWM signals to drive a thyristor-power-regulator array / phase conrtrolled modulator.
I am sure that out there are many home mechanics who would welcome such a circuit.
Anybody out there who likes to design it for us and (if needed) programs a sketch for a controller?
Thanks in before,
Martin Krahn