Anyone else finding the Renogy 40A MPPT a bit twitchy on partial shade?

Been noticing something similar with mine, though I'm running it on a garden office setup rather than a van. When one of my panels gets even partial shade from a nearby tree, the controller seems to hunt around constantly rather than settling on a stable operating point. Output drops way more than I'd expect just from the shading itself.

Wondering if it's the sweeping algorithm struggling to distinguish between local and global MPP — that's where cheaper MPPT units often fall down compared to something like Victron. The SmartSolar handles it much more gracefully from what I've seen on the forums.

A few things worth trying if you haven't already:

• Check your firmware is up to date (Renogy did push a fix a while back that apparently helped with this)
• Try adjusting the voltage sensing wiring if you're running long cable runs
• Some people swear by wiring shaded and unshaded panels to separate strings

What's your panel arrangement like? Series, parallel, or a mix? That makes a huge difference with partial shade — series strings are notoriously sensitive to it, which is why I went parallel on mine after having similar grief.

Curious whether others on van setups are seeing the same behaviour or if it's worse on fixed installs. Also interested whether anyone's actually switched from the Renogy to something else and noticed a real-world difference rather than just spec-sheet gains.

@KenCross welcome to the forum, great first post and really glad you've brought this up — partial shade behaviour is one of those things that catches a lot of people out and it's worth digging into properly!

I've seen exactly this on my narrowboat setup. The Renogy 40A does struggle when shading hits mid-string — it can't always find the true MPP when the power curve gets irregular from partial shade.

A few things worth trying:

• String configuration matters massively — are your panels wired series or parallel?
• Parallel tends to handle partial shade far better on these controllers
• If you're committed to series, a proper Victron SmartSolar handles shade-induced multiple power peaks much more gracefully

What's your panel arrangement currently? That'll help narrow down whether it's a wiring issue or the controller genuinely struggling.

Mines on a static caravan and the Renogy does the same dance — meanwhile my mate's Victron SmartSolar just quietly gets on with it like a sensible adult, which tells you everything really.

@KenCross classic Renogy behaviour — it's basically doing a confused little jig every time a cloud drifts past. Mine did the same on the boat before I swapped it out.

The issue is the MPPT algorithm is fairly aggressive about rescanning the power curve. Fine in full sun, slightly unhinged under partial shade. It keeps "finding"

@BrianBrown 😂 "confused little jig" is exactly it

Had the same drama on my van conversion before I swapped over to a Victron SmartSolar 100/30. Night and day difference — the Victron just gets on with it quietly in the background like a sensible adult.

The Renogy isn't bad exactly, more like... enthusiastic? It's really trying its best bless it

If you're stuck with it for now, worth making sure your panel strings are matched as closely as possible — mixing orientations or wattages makes the twitchiness ten times worse in my experience. Bought that lesson the hard way on the shepherd's hut build 🙃