Yes, you can wire two Victron Orion-Tr Smart 12/12-30 DC-DC chargers in parallel for a combined 60A of alternator charging. Victron officially supports this configuration, but there are specific requirements for cable sizing, synchronisation, and mounting that you must follow. This guide covers everything you need to know to do it properly.
Why Run Two Orion-Tr Smart in Parallel?
The Orion-Tr Smart 12/12-30 delivers a maximum of 30A — enough for most campervan leisure batteries. But there are situations where 30A isn't sufficient:
- Large lithium banks (300Ah+). A 300Ah LiFePO4 battery can accept 100A or more of charge current. At 30A from the alternator, you'd need 10 hours of driving to fully charge from 20% SOC. At 60A, that drops to 5 hours — a much more practical timeframe for UK touring.
- Primary charging from driving. If you don't have solar panels (or they're a small supplementary array), the alternator is your main charging source. Faster alternator charging means less dependency on hookup.
- Short driving days. If your typical drive is only 1–2 hours, you need a high charge rate to put meaningful energy into the battery in that time.
- Running heavy loads. If you're running a compressor fridge, diesel heater, inverter, and other loads while driving, some of that 30A goes to powering those loads rather than charging the battery. A second unit ensures the battery still receives a strong charge.
Requirements for Parallel Operation
Victron's official requirement is straightforward: both units must be the same model. You cannot parallel an Orion-Tr Smart 12/12-30 with an Orion-Tr Smart 12/12-18. Both must be 12/12-30 units (or both 12/12-18, though paralleling two 18A units for 36A is less common).
Critical: Equal Cable Lengths
This is the single most important rule for parallel DC-DC chargers. The cables from each charger to the battery must be exactly the same length and gauge — both on the input side and the output side. Unequal cable lengths cause unequal voltage drops, which means one charger works harder than the other. Over time, this leads to:
- Uneven charge phase transitions (one unit in bulk while the other is in absorption).
- One unit running hotter and wearing out faster.
- Reduced total charge efficiency.
The easiest way to ensure equal lengths is to mount both chargers side by side and run their cables to a common bus bar, using the same length of cable for each unit.
Wiring Diagram for Two Parallel Orion-Tr Smart
The parallel wiring layout uses bus bars on both the input and output sides:
Input side (starter battery):
Starter battery (+) → 35mm² cable → Input bus bar → 25mm² cable (equal length) → Unit 1 INPUT (+)
Input bus bar → 25mm² cable (equal length) → Unit 2 INPUT (+)
Output side (leisure battery):
Unit 1 OUTPUT (+) → 25mm² cable (equal length) → Output bus bar
Unit 2 OUTPUT (+) → 25mm² cable (equal length) → Output bus bar
Output bus bar → 35mm² cable → Leisure battery (+)
Negative cables follow the same pattern — equal lengths from each unit to a common negative bus bar, then a single cable to the battery.
Cable Sizing for 60A
With two units delivering 60A combined, your common cables (bus bar to battery) must handle the full 60A. Here are the minimum cable sizes:
| Cable Section | Current | Min. Gauge (up to 2m) | Min. Gauge (up to 5m) |
|---|---|---|---|
| Starter battery to input bus bar | ~70A (input side, accounting for efficiency) | 35mm² | 50mm² |
| Input bus bar to each charger | ~35A each | 25mm² | 25mm² |
| Each charger to output bus bar | 30A each | 25mm² | 25mm² |
| Output bus bar to leisure battery | 60A combined | 35mm² | 50mm² |
Note on input current: Because the Orion-Tr Smart operates at approximately 87% efficiency, the input current is higher than the output current. Two units drawing enough power to deliver 60A at the output will pull approximately 70A from the starter battery. Size your input cables and fuses accordingly.
Fusing Requirements
Each charger needs its own individual fuse, plus the common cables need protection:
| Fuse Location | Fuse Rating | Purpose |
|---|---|---|
| Starter battery to input bus bar | 80A mega fuse | Protects main input cable |
| Input bus bar to Unit 1 | 40A midi fuse or mega fuse | Individual protection for Unit 1 input |
| Input bus bar to Unit 2 | 40A midi fuse or mega fuse | Individual protection for Unit 2 input |
| Unit 1 output to output bus bar | 40A midi fuse or mega fuse | Individual protection for Unit 1 output |
| Unit 2 output to output bus bar | 40A midi fuse or mega fuse | Individual protection for Unit 2 output |
| Output bus bar to leisure battery | 80A mega fuse | Protects main output cable |
The individual fuses per unit allow you to isolate one charger for maintenance without disabling the other. The main cable fuses protect against short circuits in the longer cable runs.
VE.Smart Networking for Synchronised Charging
When two Orion-Tr Smart chargers operate in parallel, they must synchronise their charge phases. Without synchronisation, one unit might enter float while the other is still in absorption — causing the same "hunting" behaviour described in our multi-MPPT guide.
Victron's solution is VE.Smart Networking, which uses Bluetooth to link the two chargers:
- Open VictronConnect and connect to Unit 1.
- Go to Settings → VE.Smart Networking.
- Tap Create Network and name it (e.g., "Alternator Charging").
- Disconnect and connect to Unit 2.
- Go to Settings → VE.Smart Networking.
- Tap Join Existing Network and select the network.
Once networked, the two units share battery voltage and charge state data. They will transition between bulk, absorption, and float simultaneously. One unit acts as the master for charge state decisions.
Adding a SmartShunt or Smart Battery Sense
For the best results, add a Victron SmartShunt or Smart Battery Sense to the VE.Smart Network. The SmartShunt measures voltage directly at the battery terminals, giving both chargers an accurate voltage reference that isn't affected by cable voltage drop. With 60A flowing through cables, even small drops make a meaningful difference to charge termination accuracy.
Configuration: Matching Settings
Both units must have identical charge settings:
- Same battery type (e.g., both set to LiFePO4)
- Same absorption voltage (e.g., both at 14.2V)
- Same float voltage (e.g., both at 13.5V)
- Same absorption time
- Same engine detection method and thresholds
Configure one unit completely in VictronConnect, note all the settings, then apply identical settings to the second unit. Even small differences (e.g., 14.2V vs 14.4V absorption) will cause the units to fight each other.
Mounting and Heat Dissipation
Two Orion-Tr Smart 12/12-30 units running at full output generate approximately 100W of combined heat (about 50W each at 87% efficiency). This is a significant amount of heat in a confined space. Mounting considerations:
- Side by side, not stacked. Mount the units next to each other with at least 50mm gap between them. Never stack one on top of the other — the lower unit's heat rises directly into the upper unit.
- Heatsink fins vertical. Orient both units so the heatsink fins run vertically, allowing natural convection to carry heat upward.
- Ventilation. The mounting location must have airflow. A sealed cupboard is not suitable. Consider adding ventilation grilles or a small 12V fan if the space is tight.
- Non-flammable mounting surface. Mount on metal or a non-combustible board. Avoid mounting directly onto plywood or wooden panels without a heat-resistant backing.
Alternator Considerations
Two chargers pulling 70A from the alternator is a significant load. Consider your vehicle's alternator capacity:
| Vehicle Type | Typical Alternator | Safe DC-DC Load | Recommendation |
|---|---|---|---|
| Small van (Caddy, Berlingo) | 70–90A | 20–30A | Single 30A unit only |
| Medium van (Transporter, Vivaro) | 110–140A | 30–50A | Single 30A unit or consider Orion XS |
| Large van (Crafter, Sprinter) | 140–180A | 50–70A | Dual 30A units feasible |
| Motorhome (Ducato, Boxer) | 150–200A | 60–80A | Dual 30A units feasible |
As a general rule, your DC-DC charger load should not exceed 50% of the alternator's rated output to leave headroom for the vehicle's own electrical systems (ECU, lights, fuel pump, AC, heated screens). On a 140A alternator, 70A for DC-DC charging is the practical maximum.
Alternative: Single Orion XS 12/12-50
Before committing to dual Orion-Tr Smart units, consider whether a single Victron Orion XS 12/12-50 would meet your needs. Here's how they compare:
| Feature | 2 × Orion-Tr Smart 12/12-30 | 1 × Orion XS 12/12-50 |
|---|---|---|
| Max output | 60A combined | 50A (configurable) |
| Total cost | £320–£400 | £220–£270 |
| Heat output | ~100W | ~12W |
| Size/weight | 2.2 kg, two units to mount | 0.5 kg, single compact unit |
| IP rating | IP43 (indoor only) | IP65 (weatherproof) |
| GX integration | Bluetooth only | VE.Direct (wired) |
| Wiring complexity | High (dual bus bars, 6 fuses) | Low (standard single-unit install) |
| Efficiency | ~87% | ~98% |
If 50A is sufficient (and for most installations it is), the Orion XS is the clearly superior solution — cheaper, smaller, cooler, simpler to install, and more efficient. The only advantage of dual Orion-Tr Smart units is the extra 10A (60A vs 50A) and redundancy (if one unit fails, you still have 30A).
When Dual Orion-Tr Smart Is the Right Choice
- You already own one Orion-Tr Smart and want to add a second for more current. Buying one more unit is cheaper than replacing your existing setup with an Orion XS.
- You specifically need 60A. If 50A from the Orion XS isn't enough and you need the extra 10A, dual units are the way to get it.
- Redundancy matters. For a liveaboard boat or a vehicle that's your primary home, having two independent chargers means a single failure doesn't leave you without alternator charging.
- You need a 24V variant. The Orion XS is currently 12V-to-12V only. If you have a 24V system, two Orion-Tr Smart 24/24-17 units in parallel (34A combined) might be your only option.
Summary
Two Victron Orion-Tr Smart 12/12-30 chargers can be wired in parallel for 60A of combined alternator charging. The keys to a successful installation are: equal cable lengths and gauges from each unit to the batteries, individual fuses on each charger, VE.Smart Networking for synchronised charging, identical configuration settings on both units, and adequate ventilation for the 100W of combined heat. Before committing to this setup, evaluate whether a single Orion XS 12/12-50 — at lower cost, smaller size, and vastly less heat — might better suit your needs.
