MPPT 250/100 Solar Charger Voltage Peak every 10 Minutes

Interesting one this — I've seen something similar on my setup, though mine manifests as a spike rather than a dip. Running a pair of Victron SmartSolar MPPT 150/35s on the shepherds hut, and every so often I'd get these oddly regular voltage excursions in VictronConnect that initially had me convinced something was failing.

Turned out in my case it was the absorption/float transition logic interacting with the BMS on my Fogstar Drift 100Ah lithium. The BMS was periodically issuing a charge disconnect signal to protect a slightly imbalanced cell, which the MPPT then interpreted as a load dump. Took me an embarrassingly long time to correlate the timestamps properly.

For the 250/100 specifically — a few things worth checking:

• Are both chargers networked via VE.Smart or running independently? If they're not properly synchronised, one can trigger a re-bulk cycle that the other then reacts to
• What's the battery chemistry setting? User-defined lithium profiles can sometimes have absorption timeout values that interact oddly at certain SOC levels
• Any chance this aligns with a BMS balancing cycle? Active balancers especially can cause momentary current spikes that look like charger misbehaviour

The 10-minute regularity does point toward a software/firmware loop rather than anything environmental like shading. Worth checking whether both units are on the same firmware version — mismatched firmware across networked MPPTs has caused stranger things.

What battery type are you running? That's probably the most relevant variable here.

@NaeClue13 that spike every 10 mins is almost certainly the MPPT doing its periodic "re-sweep" of the IV curve to find the true MPP — Victron calls it a sweep interval and it's completely normal behaviour, though it looks alarming on VRM graphs! 🔍

On my shepherds hut setup I initially panicked seeing similar spikes until I realised the charger was just being diligent rather than throwing a wobbly. Worth checking your absorption voltage setpoint though — if the spike is pushing above that, something's misconfigured. Also double-check your battery profile in VictronConnect matches your actual cells (especially if you're running Fogstar or similar lithium that needs a tighter ceiling).

If spikes persist outside normal sweep behaviour, a quick firmware update via VictronConnect often sorts it.

@BoatPaddy is spot on about the re-sweep, but worth adding that on the 250/100 specifically, Victron's default re-sweep interval is actually configurable in VictronConnect — I've had mine set to 15 minutes on the motorhome setup to reduce the disruption to sensitive loads.

One thing I'd check: if your spike is upward rather than a dip, that sometimes indicates the MPPT momentarily losing battery voltage reference — particularly if you're running long DC cable runs without adequate fusing close to the battery. A brief disconnect of the regulation feedback can cause the controller to momentarily overshoot.

What's your battery chemistry? On LiFePO4 with a tight BMS voltage window (like the Fogstar Drift cells I run), those spikes can occasionally tickle the overvoltage protection and cause nuisance disconnects.

@SimonKelly is right but nobody's mentioned the obvious gotcha — if your battery cables are undersized, that re-sweep current surge will show a bigger apparent voltage spike than it should, because you're measuring voltage drop across the cable resistance, not just the battery. Check your cable run length and cross-section against Victron's own calculator before assuming the MPPT is misbehaving. Had exactly this on my motorhome build with 35mm² cable that was "fine" until it wasn't — swapped to 70mm² and the spikes halved. Also worth checking your Fogstar/BMS isn't triggering a brief load disconnect in response to the sweep, which can look identical on a graph but has a completely different fix.

Ran into this exact thing on my van build last year — drove me absolutely mental for weeks. Spent ages convinced the Fogstar cells were playing up before I finally twigged it was the re-sweep all along.

One thing nobody's mentioned yet: check your VE.Direct logs rather than just eyeballing the app. The spike looks absolutely dramatic on the live graph but when I exported the data it was lasting maybe 800ms. Completely irrelevant to the battery in practice.

@FormerCop raises the cable point which is bang on — I'd also add that if you've got a BMS with aggressive overcurrent protection, it might actually trip during that brief event and then recover so fast you think you imagined it. Had that happen on my boat setup too. Two completely different systems, same baffling symptom.