Per-panel charge controller?

[memilanuk]

Hello all,

I was recently checking out a YT vid w/ accompanying blog post, where they had separate MPPT charge controllers, one for each solar panel on the roof.

The reasoning was presented as being to prevent shading of any one array from affecting any of the others. Later I wondered if it would also be to add some redundancy (no single point of failure) and/or in some instances whether multiple smaller controllers might be cheaper than a single larger controller (within the same brand/line, in this case Victron). It does seem like there would be some additional complexity in terms of the number of wires having to be ran in from the roof to the charge controllers, etc.

I'm still very new to the whole solar thing, so this was an interesting new idea to me. No dog in the fight one way or the other, as the saying goes. I'm curious, though, how much this gets used in actual practice, and what other pros/cons might be?

Thanks!

 

[Hedges]

Panels can be had for $50. Charge controllers for $100

Potentially, efficiency could be greater with more watts of panels on a given charge controller.

Redundancy can improve reliability. But so can quality.

Single series string of panels into one MPPT can already keep other panels working if one is shaded. It can also harvest power from remaining un-shaded 1/2 or 2/3 of partially shaded panel by means of bypass diodes. Parallel panels or charge controller per panel won't do that (unless 2/3 is still sufficient voltage for charging.)

MPPT will harvest more power over a broad range of conditions than PWM. Multiple cheap probably means PWM.

I have 5000W PV going to an AC coupled GT inverter that cost me $500 (new old stock). MTBF should be > 20 years. Can you match that with individual SCC?

For DC coupled, maybe 2 or 3 SCC is good. Just like my large grid-backup system has multiple AC coupled inverters.

 

[fazeshift]

"Solar optimizers" are probably what you saw in the video. The maximum power point will differ per panel, but a MPPT controller treats the array as one. It makes sense to see an output gain by adding MPPT capabilities at a more granular level. An in-line solar optimizer is one way to do so.

Another way is internal to the panel. There are chips with MPPT (E.g., MAX20801) that can take the place of the bypass diodes. That has the added advantage of being able to have multiple MPPT groups within a panel, as most panels are made up of 3 strings of 20-24 series cells.

 

[JMc]

My a-frame trailer has two roofs each with solar panels, 600W total. The panels on one roof are hidden when it’s in the folded (tow) position and could possibly shaded when the roof is set up for use, so I have separate charge controllers.

 

[memilanuk]

"Solar optimizers" are probably what you saw in the video.

They did mention (and link to an article on) 'panel level optimizers' by way of justification, but that seemed to be (according to the article) something more oriented (for now) at residential type installs. They were specifically using three Victron 75/10 MPPT controllers.