Anyone else's Victron MPPT reading wildly different to actual panel output?

My Victron SmartSolar 100/30 is telling me I'm pulling 18A from my roof panels but my clamp meter says closer to 11A — on the narrowboat, two 200W Renogy monos wired in parallel, so theoretically should be hitting nearer 20A in decent sun.

Checked connections, re-crimped the MC4s, still the same story. Battery's a Fogstar Drift 100Ah LiFePO4 and absorption kicks in around noon so it's not like she's hungry — wondering if the MPPT is just showing potential amps rather than what's actually flowing into a near-full battery.

Is the Victron display lying to me, or is my clamp meter having a moment?

@ThistleKen — had something similar on the motorhome last summer. Few things worth checking:

• Is your clamp meter AC-rated only? A lot of cheaper ones give garbage readings on DC
• Where exactly are you clamping? If it's on the combined positive after the controller, you'd expect different figures
• What's the battery state of charge at the time? If they're near full the MPPT will be throttling back and the panel voltage climbs — the controller's reported current can look odd during absorption

Also worth checking whether your Renogy panels are actually matched — parallel wiring means a weaker panel drags the other down, so real-world output can be well below the 400W theoretical.

What does the Victron app show for PV voltage vs battery voltage at the moment you're seeing the discrepancy?

@ThistleKen — worth checking where exactly you're clamping. On a parallel setup, if you're only measuring one string rather than the combined feed into the controller, you'll get a lower reading that looks like a discrepancy but actually isn't. Try clamping the single wire running from the combiner/junction point into the MPPT instead.

Also, Victron's instantaneous readout can spike briefly during sweeps — the Connect app history graph will give you a more honest average figure to compare against.

One other thing: what cable run length have you got between panels and controller? On a narrowboat install I've seen enough voltage drop over longer runs to make clamp readings seem off relative to what the MPPT reports. Worth ruling out before assuming the Victron's playing up — they're generally pretty accurate units.

@ThistleKen — just to add to what @WonkyRigger and @MarineCallum have flagged, it's also worth checking whether your Renogy panels are getting any partial shading. On a narrowboat the roof situation changes constantly — bridges, trees, marina buildings — and even a small shadow on one cell can drag down output significantly in a parallel config without it being obvious.

Also, have a look at the cable run between panels and controller. Undersized or corroded connections will cause voltage drop that skews what the MPPT "thinks" it's receiving versus what's actually arriving. Narrowboat environments are brutal for connector corrosion.

The Victron VictronConnect app will show you live IV curve data if you haven't already dug into that — far more useful than a clamp meter for diagnosing where the discrepancy actually lies.

Has anyone actually checked the battery voltage at the point of measurement vs at the MPPT terminals? I had a similar head-scratcher with my Fogstar Drift 100Ah — turned out I had a dodgy connection causing a voltage drop between the controller and battery, which was throwing everything off.

Also @ThistleKen — what does the Victron Connect app show for panel voltage and wattage simultaneously? If the voltage looks right but watts seem inflated, I'd be suspicious of a firmware quirk. There was a known issue on older SmartSolar firmware versions that caused odd reporting.

What firmware version are you running on the 100/30?

@ThistleKen — one thing nobody's mentioned yet: have you verified your clamp meter is actually rated for DC? A lot of cheaper clamp meters are AC-only, and even some that claim DC capability can be pretty inaccurate at lower currents. Worth double-checking the specs on yours.

Also, the Victron's current reading is measured internally at the MPPT itself, so if there's any resistance in the cabling between your panels and the controller — dodgy connections, undersized wire, corroded terminals — you could see a voltage drop that affects what your clamp is picking up depending on exactly where you're measuring. Narrowboat environments are brutal for connections with all that vibration and damp. I'd give every terminal a proper inspection while you're investigating.

@BordersSolar makes a really good point about the clamp meter — caught me out years ago that one.

Worth adding: on my setup I noticed the Victron app's "panel power" figure can lag a bit and sometimes shows a peak reading rather than a live average. Try watching the History tab instead and comparing daily yield figures — those tend to be more honest.

Also, two 200W monos in parallel means your theoretical max is around 11–12A anyway (depending on Isc), so your clamp meter reading might actually be closer to correct than the MPPT display. The 18A figure does sound suspicious tbh.

What firmware version is the SmartSolar on? There were some reporting quirks in older versions that Victron quietly patched.