MPPT 100/20 is dead

Had something almost identical happen with my Victron MPPT 100/20 on the narrowboat last summer. Woke up one morning and the whole unit was completely dead — no LEDs, no Bluetooth, nothing showing in VictronConnect. Battery was sitting at a healthy 12.7V and the panels were putting out fine.

First thing I did was check the inline fuse on the battery cable — blown. Replaced it, same result. That's when I started suspecting something more serious had gone internally.

Turned out there was a fault on my battery side wiring that had sent a spike back through the controller. Victron's protection is good but it's not bulletproof.

A few things worth checking if you're in the same boat (no pun intended):

• Check both fuses — there's sometimes one people miss on the PV input side depending on your setup
• Inspect the wiring for any signs of heat damage or a short — the controller dying can sometimes be a symptom rather than the root cause
• Try connecting directly to a known-good 12V battery with no panels attached, just to rule out a total internal failure
• Contact Victron support — they're surprisingly helpful and if it's within 5 years there may be warranty options

Mine was out of warranty so I sent it off to a Victron dealer for inspection. They confirmed the internal MOSFETs had gone. Ended up having to replace the unit unfortunately.

Anyone else had this happen? Curious whether others have managed to revive one or if it's generally a write-off once the internals blow. Also wondering if a SmartSolar 100/30 would be a worthwhile step up as a replacement given the price difference isn't huge now.

@RobBennett93 Worth checking the VE.Direct port first before writing it off completely — a corrupted firmware flash can sometimes render the unit apparently dead whilst the hardware itself is fine. Victron's MK3-USB interface and VictronConnect can often revive them if there's still any life in the comms chip.

Also double-check your battery negative connection at the controller itself; a loose or corroded negative can cause exactly this symptom, particularly on narrowboats where vibration and damp do their worst.

If it genuinely is dead, Victron's warranty support through UK distributors like Bimble Solar or Current Connected has been solid in my experience — even slightly out of warranty they're often reasonable. Don't bin it without at least getting a diagnosis.

@RobBennett93 Before you assume the unit itself is done, check the fuse on the battery cable — sounds obvious but the 100/20 has an internal resettable fuse and an external one that often gets overlooked. I lost a full afternoon diagnosing my setup in the motorhome before realising the ANL fuse on the positive cable had simply blown cleanly, leaving absolutely no visible signs of failure.

Also worth confirming: did the PV array voltage ever exceed 100V? Even briefly. On a cold morning with multiple panels in series, Voc can spike beyond the rated input and take the unit out silently. Victron's warranty process is actually reasonably painless if you bought through an authorised UK dealer — Bimble Solar and Solar Voltage are both good for this. Keep your purchase receipt handy.

@RobBennett93 Had almost the exact same situation on my boat two winters back — completely dead 100/20, not a flicker of life. Turned out the positive battery cable had developed a hairline fracture right at the lug, so it was making just enough contact to look fine but not enough to actually power the unit. Flexing the cable slightly confirmed it.

Worth also checking whether the controller's internal protection has tripped due to a reverse polarity moment — sometimes a brief wiring mishap during installation or maintenance can silently kill it without any obvious sign of damage. Victron's warranty claim process through their UK distributors is actually pretty painless if it does turn out to be a fault rather than user error.

@RobBennett93 What's the actual wiring setup? Panel cable length, gauge, and did you use the built-in terminals or an external fuse holder on the PV side? Asking because I had a 100/20 on my narrowboat go completely silent and it turned out to be a failed solder joint on the PV input internally — caused by repeated thermal cycling in a poorly ventilated locker. Unit looked dead but was actually drawing a tiny trickle when I measured properly. Victron's warranty process is decent enough if it's genuinely failed, but they'll want to know you've ruled out wiring faults first. Where did you mount it?

@RobBennett93 worth checking the VE.Direct port too — had mine go completely dark on the tiny house build and it turned out the unit was actually fine, just the comms chip had thrown a wobble. Plugged in via VE.Direct to a laptop running VictronConnect and it showed up straight away, just no Bluetooth.

Also — what's your battery voltage set to? If it's drifted to the wrong profile it can occasionally cause weird shutdowns. Had a Fogstar 12V LiFePO4 trip the BMS and take the MPPT with it, looked totally dead but was fine once the BMS reset.

Don't bin it yet.