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Inverter install for load shedding at home


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So I am in the process of installing an inverter to carry some of the load in our house during load shedding (lights and one or two plug points)


The setup is as follows:

1 x 3Kva plus Mecer 24volt inverter

2 x OmniPower 260aH 12volt batteries

1 x Victron energy battery monitor BMV - 702


I have mounted the inverter, battery monitor and a sub DB board. I am awaiting the arrival of my batteries in the new year, then I will finish the wiring and commission the system.

I had a couple of questions if anyone out there is able to assist.


The solar charger mode specs are as follows:

Rated current: 60amp

System voltage: 24volts DC

Solar operating voltage range: 30-115volts DC

Max solar voltage: 145volts DC


Is there a calculation to see how many solar panels I require to charge the batteries from 50% DOD to full charge?









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Your load is unknown.


The battery is 260 Ah @ nominal 24V. This gives 130 Ah @ 50% D.O.D. Ignoring losses, this translates to a 10 hour current of 13 Amps or 5 hours @ 26 Amps.


Nominal 24 V @ 26 A gives you 624 Watts during the 5 hours. If you were using Wp and track the sun, this value of PV is close, BUT with stationary panels,Wp is only obtained when the sun shines perpendicular onto the PV panels, therefore you are going to need more capacity than this. As a rough rule of thumb, I'll double on the requirements seeing that your efficiency in converting from DC to AC is also around 80%.


In stead of 624 W, your initial requirement is then 624 W divided by 0.8 = 780 W. Double this and we get 1560 W which is just more than 6 x 250 Wp PV panels.


You have a 3 kVA inverter which can take pv of 30V to 115 V (with built-in charge controller I presume). 3000 divided by 115 gives 26 Amps of solar.


If you use 6 panels in two series rows of 3 and connect them in parallel, you should be very close.

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I consider it more important to have enough solar power to supply the average load during the day. if load shedding is during the evening then Utility power will charge the batteries anyway. Solar power is also dependent on the weather.


PV panel rating for the 3kva 24V plus is 1500W, default maximum charging current is 60A (02 setting) but should be set to 20A or 30A (Utility and PV combined).

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