Dual Solar Panels

Basil48192

I have the factory (105W) solar panel and controller on my 2021 T@B 320S camper.  I also added a 200W suitcase panel with a second Victron controller.  I just returned from an amazing camping trip in the northern part of lower Michigan and the weather was spectacular.  I put my suitcase out in direct sun and was getting around 180 watts...which is probably the best performance I've seen.  At the same time, my factory roof-top panel was showing '0' watts.  I covered the suitcase panel, and the roof panel became active.  Question:  Is it common that the smaller panel to back down if the larger panel is providing sufficient charging capacity?  Thank you in advance!

techietab

I really struggle to get anything out of the stock rooftop Sunflare panel in anything but the most ideal conditions, and it's barely logged anything since early August for me. It's almost never able to hit the +5v differential above the battery charge state in order to kick the Victron MPPT controller into charge mode.

You're probably running into the same issue.

Like you, I also have a 200W suitcase panel hooked up to a secondary Victron MPPT controller, and have way more success with this config. I also have a couple of 100w suitcase panels that support connecting in parallel, and in the next few weeks I'm probably going to disconnect the rooftop panel and re-route the stock Victron controller to an external SAE port so I can have all of my suitcase panels connected simultaneously.

Denny16

If the two Victron controllers are networked together, using the Victron phone App, priority will be given to the panels providing the most current.  If both sets are close in output, then they can be combined to both charging the battery.  It all depends on the battery charge state, and the current output of the PV panels, from what I understand.
 Cheers 

ScottG

While I suspect the panels themselves don't back down, the controllers probably do. The suitcase system in full sun may have tricked the rooftop system into thinking the battery was fully charged (or even overcharged), causing the rooftop controller to shut down any current from its side. Once you removed the charge from the suitcase, the rooftop controller saw the batter as discharged kicked on to provide whatever limited charge it could.

This is just a guess on my part. I only run a 100W suitcase, but even with a single system I've seen voltage and amperage reading fluctuate wildly even though lighting conditions were steady.

techietab

Denny16 said:

If the two Victron controllers are networked together, using the Victron phone App, priority will be given to the panels providing the most current.  If both sets are close in output, then they can be combined to both charging the battery.  It all depends on the battery charge state, and the current output of the PV panels, from what I understand.
 Cheers 

Panel outputs don't need to be consistent across multiple networked Victron MPPT controllers for the controllers to both actively charge the same battery bank. If two or more charge controllers are in a ve.smart network, one of them is elected master and will direct the charge state on the other controllers to avoid conflicts. This is, of course, assuming both isolated sets of panels hit a high enough output voltage to trigger charging.

I've had a tiny trickle of watts coming in from my rooftop panel while external panels were throwing > 150+ watts at the same battery bank, meanwhile the stats from my Smart Shunt make it clear that the input amperage from both controllers is additive (e.g. controller 1 reports 10A output, controller 2 reports 3A output, Smart Shunt reports surplus of roughly 13A). Same behavior happens if I turn on my Victron IP22 while the MPPT controllers are charging via solar, and the MPPT controllers sync to the charging phase (bulk/absorption/storage) that the IP22 is in.

That said, you *do* want roughly similar panel outputs on the circuit north of each MPPT controller lest an underperforming panel become a bottleneck.

Denny16

Thanks for confirming and expanding on how the two controllers that have been networked together.  I was keeping my response on the simple side, nice to have the details.
 Cheers 

Basil48192

Thank you to everyone...that helps a lot!