I will have an off grid solar panel system to run my deep well 5,5 Hp water pump. I already got 24 of 250Wp 36,3 Voc panels and 3 phase Delta VFD C2000 inverter/driver. for this system I need to wire all the panels in serial to get 540-800 Voc for pump driver. This part is ok.
I want to use another 5KVA inverter with some batteries to run devices (Tv, Fridge, …) in a small village house and 1-2 Hp small 230v motors for spraying (only during the day). I already have 24 panels for waterpump and I want to use those panels when I don't need water. However inverter can take up to 90 Voc 50 amps to charge 48V batteries. I can use some relays and make few parallel panel until 50 amp, but this system might be risky in the case of a relay fault.
If it is possible I want to reduce high Voc to match 90 Vmax 50 amps inverter input for solar panels.
Efficiency of dc to dc conversion is not and issue since I will have plenty of panels waiting all day for nothing.
Can you please give me and idea how can I do this with low budget?
Best Answer
If I correctly understand what you're trying to do, it seems that connecting a DPDT relay to each pair of panels would achieve what you want:
simulate this circuit – Schematic created using CircuitLab
Activate relays as needed to power the LV inverter. If a relay should drop out for some reason, there's no danger of exceeding the input voltage rating of the inverter.