Victron 75/15 specs

[Boisblancboy]

Forgive me as math isn’t my strong suit thus my question. So this may be very stupid.

Reading the specs for the victron 75/15 charge controller I see the different in PV power from 12v to 24v jumps from 220w to 440w.

But looking at 24v panels you’d easily have way to high of VOC trying to get near that 440w.

At least with 12v panels you could stay under(not much) with 3 in series.

So if someone could explain this all and what it means I’d appreciate it.

Sizing all this stuff makes my brain crumble.

 

[sunshine_eggo]

It's NOT referring to 12V or 24V panels.

MPPT 75/15:

75 means maximum of 75Voc PV INPUT allowing for cold temperature voltage increases.
15 means 15A output to battery.

220W is output on a 12V BATTERY
440W is output on a 24V BATTERY

15A at 12V is half the power of 15A at 24V.

 

[KnobCountry]

You would need to post the panel specs to do the math.

If a 100w panel has voc of 21v you could squeeze 3 in series for 63v. You wouldn't want to get much closer to the max 75 or risk burning it out.

So if you had 6 of these theoretical panels you could do 2 parallel strings of 3 in series.

3s2p

The victron will adapt to the availability of power / light and find the optimal power point.

Stay 10-15% below the voc rating to be safe. I wouldn't go above 65v on a 75/15 unit.

If your panels are 45v voc you can do only 1 in series.

The victron will find and lock on to the most pv VA it can based on conditions.

If you had 24v voc panels you wouldn't do more than 2 in series as 3 is way too close to the max input of 75v. A crisp clear cold day could fry the input.

Your still getting the power because in parallel the amps stack.