The Victron SmartShunt is the most popular battery monitor for campervans, boats, and off-grid systems. But it only works correctly if installed properly — and the most common mistake is getting the negative bus bar wiring wrong. This guide ensures you install it right first time.
How the SmartShunt Works
The SmartShunt measures current by detecting the tiny voltage drop across a precision shunt resistor. This shunt must be the only path between your battery's negative terminal and all your loads and charge sources. If any cable bypasses the shunt, the readings will be inaccurate.
This is the single most important rule: every wire connecting to battery negative must go through the shunt.
What You Need
- Victron SmartShunt (500A or IP65 model)
- A short, heavy-gauge cable from battery negative to one side of the shunt (6mm² minimum, 16–25mm² recommended)
- Your phone with the VictronConnect app installed
- A small cable from the shunt's "B+" terminal to battery positive (included — thin red wire with fuse)
- Appropriate ring terminals or lugs for your cable sizes
Step 1: Plan Your Negative Bus Bar Layout
Before touching any cables, plan the wiring layout. You need to understand which side of the shunt is which:
- "BATTERY MINUS" side: Only the battery negative cable connects here. Nothing else.
- "SYSTEM MINUS" side: Everything else connects here — all loads (fuse box, inverter, DC-DC charger) and all charge sources (MPPT solar controller, mains charger).
A common approach is to mount a negative bus bar on the system side. All your loads and charge sources connect to this bus bar, and a single heavy cable runs from the bus bar through the shunt to the battery negative.
Step 2: Disconnect Everything
Before installation, disconnect all loads and charge sources. Switch off your MPPT controller, inverter, and any other devices. Disconnect the battery negative terminal last.
Safety: Always disconnect the negative terminal first when removing, and reconnect it last when installing. This prevents accidental short circuits.
Step 3: Mount the SmartShunt
Mount the shunt close to the battery in a dry, accessible location. The SmartShunt is not waterproof (unless you have the IP65 model), so avoid locations that may get wet.
The shunt has two M10 bolts (or M8 on some models) for the main current-carrying cables, plus a small connector for the voltage sense wire and temperature sensor.
Step 4: Wire the Battery Side
Connect a short, heavy cable from your battery's negative terminal to the "BATTERY MINUS" bolt on the shunt. Use appropriately sized cable — at least 25mm² for systems that might draw high currents (inverters, etc.).
Critical rule: Only the battery negative cable connects to this side. No loads, no chargers — just the battery.
Step 5: Wire the System Side
Connect all your negative return cables to the "SYSTEM MINUS" bolt on the shunt, or to a bus bar connected to this bolt. This includes:
- Fuse box / distribution panel negative
- Inverter negative
- MPPT charge controller negative
- DC-DC charger negative
- Mains charger negative
- Any other device that connects to battery negative
If you have many connections, use a negative bus bar bolted to the system side of the shunt. This keeps things tidy and avoids overloading the shunt's bolt with too many lugs.
Step 6: Connect the Voltage Sense Wire
The SmartShunt comes with a thin red wire (with an inline fuse) that connects from the shunt's "B+" pin to your battery positive terminal. This allows the SmartShunt to measure battery voltage accurately.
Route this wire neatly and connect it to the battery positive (or a fused positive bus bar). The inline fuse protects against short circuits in this sensing wire.
Step 7: Reconnect and Power On
- Reconnect the battery negative cable to the battery terminal (through the shunt).
- Reconnect all loads and charge sources.
- The SmartShunt should power on automatically — look for the small blue LED near the connector.
Step 8: Configure via VictronConnect
Open the VictronConnect app and connect to your SmartShunt via Bluetooth (default PIN: 000000).
Essential Settings
- Battery capacity: Enter your battery bank's total capacity in Ah. For a 200Ah lithium battery, enter 200.
- Charged voltage: The voltage at which the SmartShunt considers the battery fully charged. For 12V lithium: 14.2V. For 12V AGM: 14.4V. For 12V GEL: 14.1V.
- Tail current: The current threshold below which the battery is considered full (when at charged voltage). Default 4% of capacity works for most setups.
- Peukert exponent: For lithium batteries, set to 1.05. For lead-acid, the default 1.25 is usually appropriate.
- Charge efficiency factor: For lithium: 99%. For lead-acid: 95%. This accounts for energy lost as heat during charging.
- Temperature coefficient: Leave at 0 for lithium. Use the default for lead-acid.
Step 9: Set Up VE.Smart Networking (Optional)
If you have Victron SmartSolar MPPT controllers or a Smart Battery Sense, set up a VE.Smart Network to share data:
- In VictronConnect, go to Settings → VE.Smart Networking.
- Create a new network or join an existing one.
- The SmartShunt will share voltage and temperature data with all networked devices.
This gives your MPPT controllers more accurate battery voltage readings (measured at the battery rather than at the controller terminals) and temperature data for charge compensation.
Common Installation Mistakes
Mistake 1: Cables Bypassing the Shunt
The most common error. If even one negative cable connects directly to the battery negative instead of going through the shunt, the SmartShunt will show inaccurate readings. Every ampere that bypasses the shunt is invisible to the monitor.
Symptom: SOC reading drifts over time, showing the battery as more full or more empty than it really is.
Mistake 2: Wrong Side of the Shunt
Connecting loads to the battery side of the shunt (or the battery to the system side) reverses the current direction measurement. The SmartShunt will show charging when you're discharging and vice versa.
Mistake 3: Wrong Battery Capacity Setting
If you enter the wrong Ah capacity, all time-remaining and SOC calculations will be proportionally wrong. Double-check your battery's rated capacity.
Mistake 4: Not Setting the Correct Charged Voltage
The SmartShunt uses the charged voltage to perform a periodic "synchronisation" — resetting SOC to 100% when the battery is full. If this voltage is set too high, the sync never happens and SOC drifts over days. If set too low, it syncs prematurely and shows 100% when the battery isn't actually full.
Verifying Correct Installation
After installation, perform these checks:
- Turn off all loads. Current reading should be close to 0A (small loads like the SmartShunt itself will show a tiny draw of 0.01–0.05A).
- Turn on a known load (e.g., a 100W light). The SmartShunt should show approximately the expected current (100W ÷ 12.8V ≈ 7.8A).
- Start charging. The current should show as negative (flowing into the battery). If it shows positive while charging, the shunt is wired backwards.
Summary
Install the SmartShunt so that it's the only path between battery negative and everything else. Battery side gets one cable only (to the battery). System side gets everything else (loads and chargers). Connect the voltage sense wire to battery positive, configure the battery settings in VictronConnect, and verify readings with a known load. Get this right and you'll have accurate state-of-charge monitoring for years.
