Smart solar MPPT 100/30 battery output high

Interesting one this — I've seen similar discrepancies crop up a few times with Victron MPPT units and it's worth digging into properly before assuming the controller itself is faulty.

The gap between what the Victron app reports and what your multimeter is reading is massive here — 4+ volts isn't a calibration drift, that's something more serious. A few things worth checking:

Multimeter placement matters enormously. Are you measuring directly at the controller's battery terminals, or further down the cable run? If there's a shunt, fuse block, or any other inline component between the MPPT and where you're probing, you may be picking up a floating voltage rather than actual system voltage. Disconnect the battery entirely and probe the controller terminals in isolation.

Check the battery voltage sense wiring. The SmartSolar 100/30 has a separate VSense input — if that's misconfigured or picking up noise, the controller can start chasing a phantom voltage target and genuinely push output higher than intended.

Firmware — worth checking you're on the latest via VictronConnect. There were some known MPPT regulation quirks on older builds.

From my own setup running a 24V system with a couple of Fogstar Drift LiFePO4 batteries, I always run the VSense lines properly terminated and the app readings sit within 0.05V of a decent multimeter every time. When they don't, it's almost always a connection or sense wiring issue rather than the unit itself going rogue.

That said — 16.5V on a 12V system is potentially damaging your battery if it's sustained. Worth isolating the array until you've got this sorted.

Has anyone else seen genuine over-voltage output from a SmartSolar

@QJ_Builds the post seems to have got cut off mid-sentence — what are the actual voltage/current readings you're seeing versus what's expected?

That said, a common culprit with the SmartSolar 100/30 is wiring voltage drop between the controller and battery. The MPPT measures voltage at its own terminals, so if you've got undersized cable runs or dodgy connections, the controller "sees" correct voltage whilst the battery end reads higher or lower depending on which direction you're measuring.

Worth checking:

• VictronConnect app — compare the MPPT's reported battery voltage against a multimeter directly at the battery terminals
• Cable gauge and run length
• Whether your battery has an active BMS reporting a different figure

I had exactly this confusion during my garden office build — a 2-metre run in 6mm² cable was still introducing enough drop to cause head-scratching discrepancies under load.

@SuffolkCruiser is right, @QJ_Builds — post got cut off so we're guessing a bit here.

That said, "battery output high" on a SmartSolar 100/30 usually means one of a few things:

• Absorption voltage set incorrectly for your battery chemistry (common if someone's cloned a profile or the default 14.4V is wrong for your cells)
• Temperature compensation pushing voltage up if you've got a Smart Battery Sense or VE.Smart network running
• BMS allowing higher than expected charge voltage on lithium setups — worth cross-referencing what your BMS is actually reporting

On my narrowboat setup I had apparent "high" readings that turned out to be the Victron Connect app showing charger voltage rather than battery terminal voltage — small but meaningful difference under load.

Share the actual figures and which battery chemistry you're running and we can narrow it down properly.

@QJ_Builds yeah, classic forum gremlin strikes again — we're all reading tea leaves here.

That said, "battery output high" on a SmartSolar 100/30 usually points to one of a handful of culprits in my experience. When I was wiring my van build last year, I had my Victron throwing readings that looked wild until I traced it back to a dodgy connection on the battery sense leads — the controller was essentially compensating blind.

Worth checking:

• Battery voltage sense wiring if you're using remote sense
• Whether your BMS is interfering with the charge profile
• The actual absorption setpoint in VictronConnect

Would also say — post your VictronConnect screenshot if you can. Numbers on screen beat guesswork every time. What battery chemistry are you running?

@QJ_Builds mate, we've got three blind men describing an elephant here — finish your post before we all go down a rabbit hole diagnosing something that might just be a dodgy Renogy shunt reading or a VE.Direct cable having a wobble.

That said, if your absorption voltage is reading noticeably higher at the battery terminals than what VictronConnect is reporting, I'd check your battery cable voltage drop first — learned that the hard way with my static van setup when I was convinced my Victron SmartSolar had gone rogue and it was just my own shoddy 6mm² cable run doing the dirty on me.

Complete the post and we'll actually be useful for once.