question

The problem is not with the Charge Controller. It's with the voltage output of the panels. Three of those Grape solar panels in series only output a Vmpp of 59.06 volts. When compensated for high panel temperature you get the 50.4 volts. I have a 48V system, and I just checked, my panel array shows a voltage input of 87 and a Voc of 94.5. These are numbers you need for a 48V system.

A 24V battery system would be much more suited to your solar array.

Pat

Maybe try using series only to raise the voltage. That way the controller will start charging earlier and finish later. The sheet currently accepts your configuration based on a nominal 48V lead acid bank. The MPPT needs +5V to start working so the sheet is saying the controller is acceptable as it won't fail on too high voltage or start self limiting on amps. It doesn't mean it is the ideal controller. As you are using lithiums with higher nominal voltages I suggest trying series to get the voltage up. Basically get that voltage up at the extremes above the dotted line ,into a more comfortable zone.

Why have you currently selected a 85 Amp output charge controller when your max current for a 48v bank is only ~24A?

That's way too big for that setup...

If you really want to keep 48v I would go all PV in series with the smallest 250v charge controller (I think 250V/60A is the smallest).

Or go a 24v system with 2 strings of 3 panels & a 100V/50A MPPT.

If you go 36v I think it's a bit odd & I don't think there are many 36v inverters out there.

Cory. I spoke to a more knowledgeable person than myself. He said he is concerned about the temperature readings. And:

This specific solar module (configuration) reaches the min. voltage at high temperatures quite early because of its temperature coeff. It will work under most conditions, but everything should be setup correctly.

My question would be is he 100% sure about the real temperature of the solar cell at maximum irradiation (he states 65°C)? Of course, if this would rise further than 65°C things get worse.

If on top of that wiring in reality could give more voltage drop (inserting connections and/ or switches) than in theory calculated, the regulator might stop charging too early missing some yield throughout the day.

My answer can only be very simple as the setup made now is too close to what is possible: I would always suggest taking one more panel in series in this case.

I also think the current rating of this MPPT is chosen quite high for this setup; input voltage as well as max. current.