However, what I'm trying to achieve is being able to run the split off the panels and only draw on the batteries a little. When the split cycles it will allow the batteries to be topped up.
With these high voltage MPPT, the controller can load the panels up in different ways to get maximum current, or voltage or other combinations. The DC-DC converter then 'adjusts' it to the programmed output voltage.
Hence why I think the high voltage panels will start much earlier in the day.... becuase when the 3 panels are at 9 volts each, the sum (27V) is in the dynamic input range of the controller.
All yet to be proven but Rob's confirmation gives me some excitement!
The 2.7kw 12v system I just rewired on an off grid house delivered 2.1kW @14v on a not so perfect solar day, yet runs all panels in parallel and is controlled by one Plasmatronics Dingo 20/20N driving 4 x 100amp capacity solid state relays. As I mentioned before, this system is put together from different capacity panels (4 x 120W and 6 x 140w) made using the older format multicrystalline panels and 8 x 200w of the newer format monocrystalline panels. 3 x 6B&S cable for the 1400w, 3 x 4mm (the original cable used for all the solar by the "professional" installer) for the 4 x 120w panels and a single run of 0 gauge (50mmsq) for the 6 x 140w.... over kill but it was the longest cable run and left capacity for more solar on that part of the roof if needed in the future.
Solar start up, as soon as the solar voltage exceeds the battery voltage current starts flowing, it does not need to reach a certain voltage for the MPPT controller to turn on or sufficient current to power the MPPT controller, the same at the end of the day and in poor weather/rain. PWM will always start first, still be running last and perform better in poor solar including rain. Why?? There are no parameters to reach to get the controller operating, just needs to be higher than battery voltage and the current flows. It is the simple KISS principle in action, nothing needs to be powered up by the incoming solar, it doesn't even require the voltage to exceed the diode resistance of 0.7v. Before anyone jumps to the flow back to the panels, it can't happen as the panels does not become a load so the solid state relay will not connect the battery to the solar panel, the safety diode inside stops that..... all to do with how solar panels are built these days
T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
