24V panels - any drawback?

[GTom]

Most panels on the market seem to provide for 12V (Vmpp around 18V). Is there any disadvantage using 24V (Vmpp around 36V) panels?

Do they suffer more from partial shading?

Higher voltage might give the MPPT better chances even when the panels are hot and relatively small (80-100W).

[john61ct]

Victron MPPT will get even more output from the higher voltage.

For shade handling, a lower panel:SC ratio will help, and the fact 75/10 and 75/15 are well under $100 now helps make that feasible.

I'd appreciate links to high-voltage panels in low power sizes (watts) like that.

And note plenty of "12V" panels get up to 21+Voc

Once you get past double that 24V is a bit of a misnomer, after that they're known as "grid-tie" panels.

[GTom]

Originally Posted by john61ct

I'd appreciate links to high-voltage panels in low power sizes (watts) like that.

Sorry, found only in German.

My guess: on a "low voltage" variant the cells are arranged to two parallel groups while the "high voltage" one has them all in series. Hence my worry that even with a 1:1 panel to controller ratio partial shading could be a severe problem.

[john61ct]

The difference is at 1:1, no matter how severe one panel is impacted, the unshaded ones are still being perfectly optimized by MPPT.

The only way to prevent shading problems completely is to eliminate the shading.

[wcapital]

Our installation, of 4 x 185 watt, "grid tie" panels at 36v, if I recall correctly w/ MPPT controller worked very very well, with little shading issues - though - they were mounted well aft of the end of the boom, overhanging beyond the stern on the top of davits - so didn't get that much shading except when underway heading towards the sun . The guys at Sun Electronics in Miami were very helpful in optimizing panel selection for size, shape (given space available) and associated electronics.....and shipping it all to St. Lucia (system was installed in Marin).

[mvmojo]

MPPT controllers are more efficient at higher voltages. The only downside is that DC voltages above about 30 volts can be heart stoppingly lethal! Just make sure to exercise caution during installation and have a PV array disconnect switch between the panels and the controller.

[Paul L]

Higher voltage panels can use smaller wire sizes.

[john61ct]

Wow Sun is famous for super cheap deals, often big lots of factory seconds.

Great to hear they actually have decent customer service.

I bet the international shipping cost almost as much as the panels?

[GTom]

Originally Posted by john61ct

I bet the international shipping cost almost as much as the panels?

Very likely as with all big & bulky items.