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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 90Vmax 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?

Thank you!

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  • \$\begingroup\$ Can you add a diagram of what you're proposing? Following the words is rather difficult. Using relays to reconfigure the panels makes sense, but I don't understand what "relay fault" you're worried about. \$\endgroup\$ – Dave Tweed Apr 20 '16 at 16:23
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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:

schematic

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.

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