Symptoms of a Shorting MPPT
You've invested in a quality Victron SmartSolar MPPT charge controller, but it keeps tripping fuses, showing error codes, or completely shutting down. The Victron app might show Error 1 (battery voltage too high), Error 2 (charger temperature too high), or Error 38-39 (input overcurrent). Some users report burned bus bars, melted connectors, or even visible arcing marks inside the unit. Before assuming the controller is defective, the cause is almost always in the wiring — not the hardware.
Cause #1: Exceeding PV Input Voltage
The most common cause of MPPT failure is exceeding the maximum PV input voltage. The SmartSolar 100/30 has a 100V maximum — but solar panel Voc (open-circuit voltage) increases in cold weather by about 0.3-0.5% per degree below 25°C. Three 200W panels in series at 40V Voc = 120V at 25°C… but at -10°C, that climbs to ~132V. If your MPPT is rated for 100V, you've just exceeded it by 32%. This can permanently damage the FET transistors inside the controller.
Cause #2: Loose or Undersized Connections
A loose MC4 connection or an undersized ring terminal creates resistance that turns into heat. Over time, heat degrades the connection further, creating a positive feedback loop that can reach arcing temperatures. Always use properly crimped ring terminals (not soldered — solder joints fail under vibration), tightened to the Victron's recommended torque specs (1.2 Nm for the 75/100 series, 2.4 Nm for the 150 series).
Cause #3: Incorrect Grounding
In a van with a metal chassis, improper grounding creates ground loops. If the negative of your solar array is bonded to the chassis at one point and the battery negative at another, stray currents flow through the chassis instead of the intended path. This can cause intermittent shorts that are maddening to diagnose. The fix: use a single grounding point — bond all negative busbars to the chassis at exactly one location, near the battery.
YOUR ENERGY PROFILE.
This document contains the sizing of your future electrical installation, calculated based on your appliances.
Inventory:
Battery
To guarantee 0WH without damaging your bank (80% max discharge):
Solar
Minimum power required to recharge your consumption:
220V AC
Maximum power (with 25% safety margin).
12V Cable Sizing Guide
Use this professional reference table to select the correct gauge (mm²) for your cables. For 12V in a van, the maximum tolerated voltage drop is 3%. Always use multi-stranded flexible automotive wire.
| Current (A) | Round trip < 2m | Round trip 4m | Round trip 6m |
|---|---|---|---|
| 5A (LEDs, USB) | 1.5 mm² | 2.5 mm² | 4 mm² |
| 10A (Fridge, Pump) | 2.5 mm² | 4 mm² | 6 mm² |
| 20A (Heater) | 4 mm² | 10 mm² | 10 mm² |
| 50A (DC/DC Booster) | 10 mm² | 16 mm² | 25 mm² |
| 100A (Inverter) | 25 mm² | 35 mm² | 50 mm² |
Fuse Sizing
The fuse protects the wire, not the appliance. Always place it as close to the power source as possible (battery or busbar).
- Wire 1.5 mm² → Max fuse 10A
- Wire 2.5 mm² → Max fuse 20A
- Wire 4 mm² → Max fuse 30A
- Wire 6 mm² → Max fuse 40A
- Wire 10 mm² → Max fuse 60A
SCHÉMA ÉLECTRIQUE
PANNEAUX SOLAIRES
0W
REGULATEUR MPPT
BATTERIE AUXILIAIRE
0 Ah
Lithium LiFePO4
BOÎTE À FUSIBLES 12V
Pompe, Leds, Frigo...
CONVERTISSEUR 220V
NON REQUI
SHOPPING LIST
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12V 6-way Fuse Box
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Digital Multimeter
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Heavy Duty Crimping Tool
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Heat Shrink Tubing
Insulation and safety
Comparison table
| Error Code | Meaning | Common Cause | Fix |
|---|---|---|---|
| Error 1 | Battery voltage too high | Incorrect battery type setting | Set correct battery profile in app |
| Error 2 | Charger overtemperature | Poor ventilation or high ambient temp | Improve airflow around unit |
| Error 38 | Input overcurrent | Array exceeds controller rating | Reduce panel count or upgrade controller |
| Error 39 | PV overvoltage | Cold weather Voc spike | Reconfigure array to reduce series voltage |
About this tool
A Victron SmartSolar MPPT that keeps tripping out or showing a fault — specifically the "short circuit detected" or "PV input protection active" alarm — has a handful of specific causes that the Victron documentation doesn't explain clearly. Based on hundreds of cases logged in the Victron Community forum, here are the diagnostic paths that resolve 95% of these issues.
First: understand what "short circuit" means in Victron MPPT context. The Victron MPPT internal protection does not just trigger on actual wire shorts. It also triggers when: (1) The MPPT detects a sudden large capacitive load on the battery side (like a large inverter turning on with discharged DC capacitors). (2) The PV array voltage collapses from high to very low suddenly (cloud edge effect, partial shading, cell cracking). (3) The battery voltage drops below the MPPT's minimum operating voltage (10.5V for 12V models) temporarily under a heavy load.
Diagnosis for the "keeps tripping" scenario: connect via Victron Connect app during operation. Watch the PV voltage and battery voltage graphs simultaneously. If PV voltage shows a sudden spike then collapse at the moment of trip, the issue is PV-side (shading, MC4 contact resistance, cracked cell). If battery voltage shows a sudden dip to below 11V at the moment of trip, the issue is battery-side — a heavy load is pulling battery voltage below the MPPT minimum threshold.
MC4 connector failure: this is the #1 undiscovered cause of "random" MPPT faults. Corroded, mismatched, or improperly crimped MC4 connectors create intermittent contact — the arc at the moment of contact can cause voltage spikes that the MPPT interprets as a fault. Test: bypass the MC4 connectors entirely with temporary clip connections and run for 24 hours. If faults stop, replace all MC4 connectors with Staubli or Amphenol MC4 and re-crimp with the correct tool.
Firmware update: Victron pushed updates from version 1.56 to 1.60 on SmartSolar models (100/20, 100/30, 150/35, 150/60) that specifically addressed false short-circuit detection events caused by fast-switching inverter loads. If your MPPT is on firmware below v1.60, update via Victron Connect → MPPT → Update. This resolves 30-40% of "random" short circuit reports without any hardware change.
Victron MPPT short-circuit protection circuit breakdown: when a short circuit occurs on the battery output of an MPPT, the internal MOSFETs switch off within microseconds. The short-circuit protection resets automatically when the fault is cleared. However, repeated short-circuit events stress the MOSFETs — if the unit "short-circuits" frequently (5+ events per day), investigate the root cause rather than relying on automatic recovery.
Wiring root causes that cause repeated MPPT battery short events: undersized or chafed cable where insulation has rubbed against a chassis metal edge (check all cable runs through van walls/floor), a corroded or carbon-tracked ANL fuse holder causing partial conduction to chassis, and battery BMS that disconnects load while MPPT is delivering high current (the sudden voltage spike from disconnection trips overcurrent protection — add a 1800μF capacitor across the MPPT battery terminals to absorb inductive spikes).
MPPT thermal shutdown vs short-circuit protection: the LED blink code distinguishes these. On Victron SmartSolar: a pulsing blue LED means normal MPPT operation. Three quick blinks then pause = high temperature shutdown (cooling required, check ventilation). Constant off with no LED = battery fault or short-circuit detected. Check VictronConnect app for fault history — it logs all events with timestamps, making diagnosis much faster than visual LED interpretation.