Advantages of High Voltage Solar Charge Controllers

Helo guys. I am inquiring about the advantages of using high voltage solar charge controllers apart from easeness of wiring and less expensive wires. Is it true that with the high voltage, this charge controllers can charge the batteries throughout the day (even during sunset and sunrise). Is is also true that it can generate good enough power to charge during rainy/cloudy seasons ?. And what could be its disadvantages ?

wady32 said:

Helo guys. I am inquiring about the advantages of using high voltage solar charge controllers apart from easeness of wiring and less expensive wires. Is it true that with the high voltage, this charge controllers can charge the batteries throughout the day (even during sunset and sunrise). Is is also true that it can generate good enough power to charge during rainy/cloudy seasons ?. And what could be its disadvantages ?

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It's actually the opposite. A high voltage controller can certainly save you on wiring costs by being able to run a single long string instead of combining multiple smaller strings in parallel.

But take for example a case where you have a Victron 150/35, versus an rs450/100. Disregarding the max charge power difference of 35A versus 100A for the example.

I am using 300W panels with a Voc of 40V.

With the 150/35 I can series three panels (120V plus safety factor for colder temps, to stay below 150V). I can parallel two strings for 1800Wp or three strings for 2700Wp (over panelling from 2kW max output at 35A). The minimum startup voltage for the 150/35 is 5V above battery voltage. So with this setup I can start charging at about 59V from the array (battery floating at 54V).

With the 450/100, I can series ten panels. Big savings in wires and combiners. However the startup voltage is 120V. And the minimum voltage to continue charging is 80V.

I haven't compared the two directly. But in marginal conditions I would think the 150/35 config would be better due to the lower startup/continue voltages required.

So in summary, there are some advantages to high voltage controllers but I don't think they are going to give you more performance in terms of dawn/dusk charging or poor solar weather when compared to lower voltage sccs.

Brucey said:

However the startup voltage is 120V. And the minimum voltage to continue charging is 80V.

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PV array voltage doesn't spend much time between zero and full string voltage. It's much closer in behaviour to an on/off switch. IOW the array will generate at/near its full voltage or little to no voltage.

This is the sort of thing you will see with PV array voltages:

wady32 said:

Is is also true that it can generate good enough power to charge during rainy/cloudy seasons ?

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As long as the MPPTs and panel strings are well matched and of good quality, being high or low voltage is neither here nor there in terms of production in rain or cloudy conditions.

For the same power rating, lower voltage strings means a higher combined current, more wires, and an additional layer of string protection is required via a combiner box once more than two strings are in parallel. Just more components overall.

Lower voltage/higher current MPPTs have more flexibility with array set ups, if for example you cannot make contiguous longer strings facing the same orientation due to space constraints.

So while it can add a little complexity and take up more room, it can also provide some redundancy.

With good quality MPPTs/solar inverters/charge controllers, then either will do a good job.