Paralleling different solar panels

[skipmac]

I have ended up with two solar panels, both 230W but one with a Voc of 18V, the other Voc 40V.

It would simplify my wiring and installation if I could connect the two panels in parallel to one controller BUT the different output voltages.

Of course this won't work with batteries but would it function with solar panels?

[rslifkin]

As far as I know, you can't connect panels of different voltage in parallel. You can probably run them in series, but someone else will have to confirm that.

[Dsanduril]

Doesn't work to the same controller.

General rule: To parallel panels need to be of the same voltage, to series they need to be same current.

The controller will pick one voltage that provides the maximum power, there are only two options: it picks 18V, in which case you lose 22/40 = 55% of the 40V panel's output, or it picks 40V, in which case you lose 100% of the 18V panel's output (gross simplification of the math, but a decent first-order estimate).

[BillKny]

The short answer to the parallel question is “NO”.

In series is electrically possible, (but check the specs on the panels for max system voltage!) but would significantly reduce the total output you would see from what you would get with two separate MPPT controllers.

Buy and install two controllers. The are not that expensive, and it will be worth it in terms of power produced.

[SunPoweredYachts]

If you do plan on wiring dissimilar panels, you should know that:

a) For series connection – the same current rating of the panels is more important
b) For parallel connection – the same voltage rating of the panels is more important

[smac999]

No way those are way off. You might even damage the 18v one if the 40v one gets up to voltage. Or the 40v one will only be around 18v and very little output.

2 small controllers is the same price as one big one anyways. And will work better. Even if Same panels.

[skipmac]

Thanks all. I didn't think it would work but a friend that is a salesman (not installer or tech) for a solar panel company said he thought it would work.

I do currently have a controller for each panel but one panel is jury rigged with the wire running across the cockpit and through the companionway. I'm pretty sure I don't want to leave it like that when I go sailing but properly installing the cable is going to be a pain as in removing lots of trim, overheads and more. Hence the silly question about paralleling two different voltage panels.

Oh well, one more job to add to the list.

[Adelie]

Originally Posted by skipmac

I have ended up with two solar panels, both 230W but one with a Voc of 18V, the other Voc 40V.



It would simplify my wiring and installation if I could connect the two panels in parallel to one controller BUT the different output voltages.



Of course this won't work with batteries but would it function with solar panels?

I believe that you CAN do it but you will get a lot less than 460W out of it even in optimum conditions.

I would wire them separately to separate controllers. Even separate PWM controllers would produce more total power than wiring them both to a single MPPT controller.