Operating voltage. Most MPPTs have a minimum string voltage rating required to operate.
yes, redundant but it can happen with some models with a much lower MPPT voltage range.
As for batteryless, I'm not sure exactly how it works but I'm not sure I'd recommend using it in that mode anyway. Better to have some battery than none.
Thanks for quick response.
Regarding battery Vs No battery, I found these descriptions in the manuals:
A. This for unit which seems to need the battery. See the word, transformerless design: "This is a multifunctional off grid solar inverter, integrated with a MPPT solar charge controller, a highfrequency pure sine wave inverter and a UPS function module in one machine, which is perfect for off gridbackup power and self-consumption applications. The transformerless design provides reliable powerconversion in compact size."
B. For the unit which says, works with or without battery: "This is a multifunctional off grid solar inverter, integrated with a MPPT solar charge controller, a highfrequency pure sine wave inverter and a UPS function module in one machine, which is perfect for off gridbackup power and self-consumption applications. This inverter can work with or without batteries." They even use the term, UPS, which implies AC to DC to charge.
Even though the description for one says compact size, the one with transformer is only 0.5Kg more.
I am not going to operate the system without battery forever. I want to build and test one section at a time without accumulating all the stuff and feel overwhelmed.
I have few more questions for you.
1. I have 4 old panels that in series gives a Voc of 150.4 (4x37.6) which is barely above the 150V the batteryless unit calls as a start-up voltage (I guess needed for the MPPT to kick in in the absence of a battery). Ironically start-up voltage is specified inside the detailed manual and not the 2-3 page spec sheet. Also the MPPT operating range is 120 to 240V which places my 4 panel op. voltage of 121.2V just little above the minimum.
2. On the otherhand, if I go for the other model, the spec. MPPT Range @ Operating Voltage is 35V to 115V (my 4 series panel string would put it at 121.2V) causing me some concern. But talking to myself, I can say the op. point is determined by the MPPT (and not the solar panels) and hence I shoud not be concerned (well, the panels will operate at a little lower voltage and hence below the possible Pmax). The MPPT operating range for the batteryless model is 120V to 240 which means my four panels barely above.
Perhaps most folks putting together a system don't analyze the situation critically as I have done and just plunge forward.
Thank you.