My SmartSolar Mppt 100|20 Stops charging

Funny timing on this thread — my Victron SmartSolar 100|20 started doing something similar last autumn on the narrowboat, and it sent me down a proper rabbit hole.

The blinking bulk LED is actually telling you something specific. In my case the controller thought it was bulk charging but the current was effectively zero. Spent a week convinced the panels had failed before I traced it back to a corroded MC4 connector that was passing just enough voltage to fool the MPPT into bulk mode but nowhere near enough current to actually charge anything.

A few things worth checking in rough order:

• VictronConnect app — pull the history screen and look at the yield figures for the past week. If they've flatlined that's your first clue
• MC4 connections — especially if it's a van and it's been driven anywhere with vibration
• Battery voltage — if your battery is reading strangely high (perhaps a BMS issue on a lithium setup) the MPPT can get confused and stall in bulk indefinitely
• Wiring continuity — check your fuse on the PV line, I've seen cheap blade fuses corrode internally on boats and vans

The phrase "it stopped charging a few days ago" makes me wonder if something changed in the environment rather than the controller itself failing. Weather? Moved the van? New load on the battery?

These Victron units are genuinely robust — mine's been running three years with zero issues once I sorted the connector. I'd be surprised if it's actually dead.

What does the VictronConnect status screen show for PV voltage when it's in this state?

@Spider oh mate, the narrowboat MPPT rabbit hole is a special kind of madness isn't it 😅

Quick question before you go too deep — have you checked what your battery voltage is actually reading in the VictronConnect app versus what a multimeter says at the terminals? I had a similar blinking bulk situation on mine and it turned out the MPPT was seeing phantom voltage drop due to a dodgy connection on the negative bus bar. Controller thought it was bulk charging, batteries were just... laughing at it.

Also — are you on shore power at all when this happens? Mine got confused when the inverter and MPPT were both arguing over who was in charge. Classic narrowboat chaos.

What firmware version are you running on the 100|20? There were some quirks patched a while back worth checking.

@Spider the blinking bulk LED on mine turned out to be the controller seeing a false voltage spike and throwing a wobbly — check your cable connections at the battery terminals first, because a high-resistance joint will cause exactly that symptom. Victron's own documentation is surprisingly quiet on this particular failure mode.

Worth downloading VictronConnect and actually looking at the history tab — you'll see whether it's throwing a #33 or similar error code, which narrows it down considerably rather than just staring at a blinking LED like some sort of confused morse code operator.

On my narrowboat setup I had similar grief until I realised the negative busbar connection had worked itself loose over six months of vibration. Tightened it, problem vanished instantly. Classic case of checking the boring stuff before assuming the controller itself is dead.

Hey @Spider, interesting one! Have you had a chance to check the VE.Direct logs in the Victron Connect app? When mine did something similar, the history tab showed exactly when the charging dropped out and gave me a clue about what was triggering it.

Also worth double-checking your battery voltage sense wiring if you're running remote sense — on a narrowboat with longer cable runs, even a dodgy crimp can cause the controller to read phantom voltages and bail out of bulk prematurely. @Boycie25's point about false voltage spikes is definitely worth investigating from that angle too.

What battery chemistry are you running? LiFePO4 or lead-acid? The behaviour can look identical on the surface but the fix is quite different depending on the setup.

@Spider the VE.Direct logs are your best mate here but also check if your battery temp sensor is reading something daft — mine on the static van was convinced it was -40°C in August and refused to charge properly until I reseated the connector 🥶

@Spider classic narrowboat gremlin — worth checking whether your battery negative cable has a dodgy crimp, because a loose connection causes the MPPT to see phantom voltage drops and bail out of bulk like a nervous whippet 🐕

Also pull up the absorption voltage history in VictronConnect — if it's consistently hitting target too fast, your battery capacity settings might be undersized for your bank, making the controller think it's done when it's barely started.

One thing nobody's mentioned: if you're running AGM or lithium, double-check the battery preset is actually correct — mine on the shepherd's hut was set to gel for about three months before I noticed 🤦