The Victron Orion-Tr Smart 12/12-30 is the most popular DC-DC charger for UK campervan and motorhome leisure battery systems. This guide walks you through every step of a typical installation — from cable routing and fuse sizing to engine detection wiring and app configuration. Follow these instructions for a safe, reliable alternator-to-leisure-battery charging setup.
Before You Start: What You Need
Components
- Victron Orion-Tr Smart 12/12-30 (isolated or non-isolated — this guide covers both)
- 25mm² (4 AWG) battery cable — red and black, enough for your cable run plus 0.5m spare
- Mega fuse holder + 40A mega fuse (starter battery end)
- Mega fuse holder + 40A mega fuse (leisure battery end)
- Ring terminals (M8 for battery posts, M6 for Orion-Tr terminals) — crimp or solder
- Cable glands or grommets for bulkhead penetrations
- Self-tapping screws or bolts for mounting the unit
- Split conduit or cable trunking to protect the cable run
- Thin wire (0.75–1.5mm²) for the engine detection signal (if using remote on/off method)
Tools
- Hydraulic or ratchet cable crimper (for 25mm² terminals — do not use plier-type crimpers)
- Drill with step bit or hole saw
- Multimeter
- Wire strippers
- Heat shrink and heat gun
- Socket set (for battery terminal bolts)
- Smartphone with VictronConnect app installed
Step 1: Plan Your Cable Route
The Orion-Tr Smart has two possible mounting positions, each with trade-offs:
Option A: Near the Starter Battery (Preferred)
Mounting in the engine bay or just behind the bulkhead minimises the high-current cable run from the starter battery to the charger. Since the charger's output is voltage-regulated, longer cable from the charger to the leisure battery is more tolerant of voltage drop (the charger compensates). This option keeps the heaviest, most expensive cable short.
Option B: Near the Leisure Battery
Some builders prefer mounting the Orion-Tr Smart in the living area near the leisure battery for easy access and monitoring. This works fine but requires a longer run of 25mm² cable from the engine bay. The IP43 rating means the unit must be in a dry, ventilated location — never in the engine bay itself.
Important: The Orion-Tr Smart is rated IP43 only. It must be mounted in a dry location protected from direct water exposure. Do not mount it in the engine bay, under the vehicle, or anywhere exposed to rain or spray. If you need weather-resistant mounting, consider the Orion XS with IP65 rating.
Routing the Cable
Route your cable from the starter battery, through the bulkhead (firewall), and to the charger location. Key points:
- Use an existing bulkhead grommet if available — many vans have spare grommeted holes for auxiliary wiring.
- If drilling a new hole, use a rubber grommet or cable gland to seal and protect the cable.
- Avoid routing near exhaust components, moving parts, or sharp edges.
- Protect the cable with split conduit where it runs through the engine bay.
- Secure the cable every 300–500mm with P-clips or cable ties to prevent chafing.
Step 2: Install Fuses
You need fuses at both ends of the cable run — within 300mm of each battery. This is a UK best practice and a requirement for boat installations under ABYC standards.
Starter Battery End
Install a 40A mega fuse holder as close to the starter battery as practical. The fuse protects the cable in case of a short circuit anywhere along its length. Connect the fuse holder to the starter battery positive terminal using a short length of 25mm² cable with appropriate ring terminals.
Leisure Battery End
Install a second 40A mega fuse near the leisure battery or at the Orion-Tr Smart's output. This protects the output cable and provides a convenient isolation point for maintenance.
Why 40A Fuses for a 30A Charger?
The Orion-Tr Smart draws more than 30A from the input side due to conversion losses. At 87% efficiency, delivering 30A at 14.4V output requires approximately 35A at 12.8V input. A 40A fuse provides adequate margin without nuisance tripping, while still protecting the 25mm² cable (which is rated for 170A+ in free air).
Step 3: Mount the Orion-Tr Smart
The unit can be mounted in any orientation — horizontal, vertical, or on its side. However, for optimal heat dissipation:
- Mount with the heatsink fins vertical to allow natural convection airflow.
- Leave at least 50mm clearance above and below for airflow.
- Do not mount on or near flammable surfaces — while the unit is designed for the temperatures it produces, keeping it away from wood panelling or fabric is good practice.
- Use the four mounting holes in the heatsink. M4 bolts or No. 8 self-tapping screws work well.
The Orion-Tr Smart 12/12-30 runs warm during sustained operation — surface temperatures of 50–60°C are normal at full output. Ensure it's not in an enclosed space with no ventilation.
Step 4: Wire the Battery Connections
Cable Gauge
For the Orion-Tr Smart 12/12-30, use 25mm² (4 AWG) cable for both input and output connections. This handles the full 30A+ with minimal voltage drop for cable runs up to 5 metres each way. For runs over 5m, step up to 35mm².
| Cable Run Length (one way) | Minimum Cable Gauge | Voltage Drop at 35A |
|---|---|---|
| Up to 2m | 16mm² | ~0.08V |
| Up to 5m | 25mm² | ~0.12V |
| Up to 8m | 35mm² | ~0.14V |
| Up to 12m | 50mm² | ~0.15V |
Connection Order
Wire in this order to minimise risk:
- Disconnect both batteries — remove the negative terminal from the starter battery and the leisure battery.
- Connect the output (leisure battery) side first. Run the positive cable from the Orion-Tr Smart output terminal through the output fuse to the leisure battery positive. Connect the negative cable from the Orion-Tr Smart output negative to the leisure battery negative.
- Connect the input (starter battery) side. Run the positive cable from the Orion-Tr Smart input terminal through the input fuse to the starter battery positive. Connect the negative cable from the Orion-Tr Smart input negative to the starter battery negative (or a suitable chassis ground point).
- Reconnect the battery negative terminals — leisure battery first, then starter battery.
Important: If using the non-isolated version and a common vehicle ground, ensure the ground path can handle the full charge current. A dedicated negative cable back to the starter battery is always the most reliable approach.
Step 5: Wire Engine Running Detection
The Orion-Tr Smart needs to know when the engine is running to prevent it from draining your starter battery while parked. There are two methods:
Method A: Voltage Sensing (Default)
By default, the Orion-Tr Smart monitors the input (starter battery) voltage. When it rises above the "engine on" threshold — typically 13.1V, indicating the alternator is charging — the unit starts. When voltage drops below the "engine off" threshold (12.8V by default), it stops after a short delay.
This is the simplest method and works for most vehicles. No additional wiring is required. However, it can be fooled by:
- Smart alternators that drop voltage below 13V while the engine is running.
- Solar chargers raising the starter battery voltage above 13V while the engine is off.
You can adjust the voltage thresholds in the VictronConnect app if the defaults don't suit your vehicle.
Method B: Remote On/Off Wire (Most Reliable)
For definitive engine detection, wire the Orion-Tr Smart's remote on/off pin to an ignition-switched 12V source. This is a wire that has 12V when the ignition is on and 0V when it's off. Common sources in UK vans:
- The fuse box — find a fuse that's only live with the ignition on (use a multimeter to check).
- The cigarette lighter / 12V socket circuit (ignition-switched on most vans).
- The D+ / alternator exciter wire (ideal, but harder to locate).
Connect the ignition-switched 12V source to the Orion-Tr Smart's H pin (remote on/off) using thin wire (0.75–1.5mm²). Then in VictronConnect, set the start/stop mode to "Remote on/off" instead of voltage sensing.
This method is completely reliable — the charger only runs when the ignition is on, regardless of voltage levels.
Step 6: Configure via VictronConnect
With the wiring complete and the starter battery reconnected, the Orion-Tr Smart's blue LED will illuminate. Open the VictronConnect app and connect via Bluetooth.
Essential Settings
- Output battery type: Select your leisure battery chemistry — LiFePO4 (lithium), AGM spiral, AGM flat plate, Gel, or a custom profile. This sets the correct charge voltages.
- Charge current: Confirm it's set to 30A (the maximum for this model).
- Engine detection: Set to "Voltage" (default) or "Remote on/off" depending on your wiring.
- Voltage thresholds (if using voltage sensing): Adjust the start voltage (default 13.1V) and stop voltage (default 12.8V) if your vehicle's smart alternator runs at non-standard voltages.
- Lockout voltage: This prevents the charger from operating if the starter battery voltage is too low. The default (12.2V) protects against accidentally flattening the starter battery.
Lithium Battery Settings
If charging a LiFePO4 battery, select the built-in lithium preset. This sets:
- Absorption voltage: 14.2V
- Float voltage: 13.5V
- No temperature compensation (lithium doesn't need it)
Check your specific lithium battery's recommended charge voltage — some manufacturers specify 14.0V or 14.4V instead. You can create a custom profile to match.
Step 7: Test the Installation
- Engine off: Verify the Orion-Tr Smart is in standby (no charging). Check the VictronConnect app — it should show "Off" or "Engine shutdown detected".
- Start the engine: Within a few seconds, the charger should detect the engine and begin charging. The app will show the charge state (bulk, absorption, or float) along with input voltage, output voltage, and charge current.
- Check current: If the leisure battery is partially discharged, you should see close to 30A charge current in bulk mode. If the battery is nearly full, you'll see lower current in absorption or float.
- Check temperatures: Run the engine for 15–20 minutes and feel the Orion-Tr Smart's heatsink. It should be warm but not too hot to touch briefly (under 60°C surface temperature is normal).
- Turn off the engine: The charger should stop within 30–60 seconds (there's a built-in delay to avoid restarting during brief engine pauses).
- Check the starter battery: Verify the starter battery voltage returns to a normal resting voltage (12.4–12.8V) after the engine is off. If it's significantly lower, check your cable connections and fuse sizing.
Wiring Diagram Description
The complete circuit is as follows, from left to right:
Starter battery (+) → 25mm² red cable → 40A mega fuse → 25mm² red cable → Orion-Tr Smart INPUT (+) → (internal DC-DC conversion) → Orion-Tr Smart OUTPUT (+) → 25mm² red cable → 40A mega fuse → 25mm² red cable → Leisure battery (+)
Starter battery (−) → 25mm² black cable → Orion-Tr Smart INPUT (−)
Leisure battery (−) → 25mm² black cable → Orion-Tr Smart OUTPUT (−)
Optional: Ignition-switched 12V → 1mm² thin wire → Orion-Tr Smart H pin (remote on/off)
Common Installation Mistakes
Mistake 1: Undersized Cable
Using 6mm² or 10mm² cable for a 30A DC-DC charger causes excessive voltage drop, especially on longer runs. The charger may not reach full output because the input voltage drops too low under load. Always use 25mm² for runs up to 5m.
Mistake 2: Missing Fuse at the Starter Battery
Some installers only fuse the leisure battery end. The fuse near the starter battery is critical — it protects the long cable run through the vehicle from a short circuit that could cause a fire. Always fuse within 300mm of each battery.
Mistake 3: Poor Grounding
A weak or corroded ground connection causes voltage drop that mimics a low battery. Run a dedicated negative cable rather than relying on the vehicle chassis as a ground path, especially on older vehicles with corroded chassis earth points.
Mistake 4: Mounting in an Enclosed Space
The Orion-Tr Smart produces significant heat (up to 50W at full output). Mounting it inside an insulated cupboard with no airflow can cause thermal shutdown. Ensure adequate ventilation around the heatsink fins.
Mistake 5: Not Adjusting for Smart Alternators
If your van has a Euro 6 smart alternator (most UK vans from 2015 onwards), the default 13.1V engine-on threshold may not work reliably. Either lower the threshold to 12.9V in the app, or switch to the remote on/off wire method for definitive engine detection.
Summary
Installing a Victron Orion-Tr Smart DC-DC charger involves routing 25mm² cable from the starter battery through the bulkhead to the charger location, fusing both ends with 40A mega fuses, mounting the unit with adequate ventilation, wiring the battery connections, and optionally connecting an engine detection wire. Configure the battery type and engine detection method in the VictronConnect app, then test with the engine running. The entire installation typically takes 3–5 hours for a competent DIY installer.
