What is the best arrangement here?

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pat21 asked Mar 2, '24

What is the best arrangement here?

I have four 500w panels, each panel has Voc of 51.7v, and Isc of 12.28A. The maximum system voltage states IEC1500W. I have a victron 150/60. This is going to go on a 24v (12v 100ah lipo, series then paralled) off grid system. If I series-parallel the panels the victron charge controller will be getting around 103v at about 25A. But then will convert this into the 24v system at 25.6 or so volts with the rest being all amps?, which is about 100amps? Is this correct and is it fine? The second issue is the panels state that the maximum system voltage should be 1500w but can I push it to 2000w (the four panels I said I've got). What are the concerns here? My second setup was to go two panels 1000w (series or parallel?) through the stated charge controller, then another charge controller for the second 1000w (two remaining panels).

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Answer 1 · 2024-03-02T11:55:59Z

nickdb answered · Mar 02 at 11:55 AM

The MPPT calculator is your friend and can answer most of these questions.

The charger is current limited at the output.

At 24V it can only produce 1440W, at 48V, double that.

Anything more will be lost and running it flat out constantly is never a good design choice.

Generally in the real world you only get, in optimal conditions, two thirds of a panels rating.

Never exceed the input voltage of 150V and use the calculator to check what that will be under cool conditions, as cold temps push the voltage up.

Your options are 4 panels in parallel or 2 x 2. You can't add more than 2 in series without exceeding the voltage limits and cooking the mppt.

The MPPT needs battery voltage +6V to start, 2 x 2 would seem the most efficient.

Watts is not a design consideration, it's all Voltage and Current.

Best to use the calculator on the MPPT web page.

At lower output voltages you generally need a bigger MPPT, or more smaller ones.

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