With the snow and ice at the beginning of the year, closely followed by lockdown, “Old Nick” has spent most of its short life on a mooring, hooked up to the shore power, unable to go anywhere.
Never having had solar panels before, I was under the naive assumption that they would just do their thing and supply the power we used during the day. I obviously understood that in the winter months their output would be a small percentage of what they produced in the summer (approximately 10%) but I had over looked one important fact.
Solar panels or to be more precise the MPPT controller will only supply power if that power is required. This is a key piece of information to remember and when you think about it, makes perfect sense. The MPPT’s job is to provide the most optimised power matching between the panels and the batteries. If the batteries are fully charged, then the MPPT backs off its output power and you see the panel voltage increase and the panel current reduce.
The screen shots below show the MPPT power output during a normal winter day, with the shore power connected and the Victron Quattro in normal combined charger and inverter mode.
As you can see the AC power taken from the shore supply fluctuated throughout the day as we boiled kettles, the water heater came on, etc. all pretty normal for a day onboard. The MPPT did provide some solar power in to the system, but because the batteries were fully charged the demand for power was low, so the current output from the MPPT averaged around 1.7A and the power taken from the solar panels averaged around 100W.
Once the penny dropped, and I appreciated that to get maximum solar power out of the MPPT, I would need to turn the charger off, I was a “man on a mission”. Every day I would switch the Victron Quattro to “Inverter Only” mode and then at the end of the day switch it back to normal Charger + Inverter mode. The results were amazing, with at least a x3 increase in solar yield.
As you can see, the AC Shore Power goes to zero as soon as the Inverter Only mode is selected and once the batteries start to discharge, the MPPT starts to increase its output power as it is now the sole battery charger. Now we are seeing an average output current from the MPPT of around 6A and average power of 300W, which over the course of the day resulted in a solar yield of between 1.5KWh and 2KWh which is pretty good for February.
After a quick chat with Rob at Ortomarine, it became clear that with a bit of extra code in his PLC and the “Ortomate” colour controller, we could have a new “Solar Eco Mode” for the Quattro that automatically switched the “Inverter Only” mode ON and OFF based on the state of the solar panels and the batteries.
With the idea planted, Rob managed to get the code written, tested and downloaded to “Old Nick”, despite his busy schedule, in just a couple of days and now I have a nice new “Solar Eco Mode” that I can select whenever we are on shore power. As well as being better for the environment, it should reduce the amount of electricity “top-up” cards that we have to purchase from the marina – win win!