Victron Orion-Tr Smart 12/12-18 wiring diagram

This is the isolated Orion-Tr Smart 12/12-18A (220 W), Victron part ORI121222120. Isolated means the input and output negatives are galvanically separated, so a starter bank on the vehicle chassis and a house bank with its own return can each keep their ground. That is why this model turns up on boats, in caravans and in trailers rather than the non-isolated range. The product family page lists it at 18 A continuous at 40 °C, a 25 A peak for 10 seconds, and a 10–17 V input.

IN + comes from the starter battery through a fuse at that battery; OUT + charges the house or leisure battery through a fuse at the house battery. On this isolated model IN − and OUT − are two separate returns, one to each bank; bonding them at the charger throws the isolation away. The remote connector's H and L pins take an engine-run signal, and the installation section of the manual carries the cable-and-fuse table for each model and run length. Those fuses protect the cable, not the charger, which has its own non-replaceable input fuse inside.

The technical reference above sizes the example run with Crimp's engine from the catalog's terminal ratings. Treat the manual's table as the floor for your own build, and open the starter to change the run lengths.

• It is rated at 40 °C and derates above that. The family datasheet gives roughly 87 % efficiency, so the rest of the throughput leaves as heat through the fins. Mount it fins-vertical with air around it; IP43 only holds with the screw terminals pointing down.
• Engine detection reads the input voltage. Euro 5 and Euro 6 smart alternators, and regenerative-braking systems, let the starter side sit below the detection threshold, and charging stops. The manual's engine shutdown detection section describes the override from an ignition-switched or D+ feed on the remote connector. Switching detection off entirely leaves only the input lockout voltage between the charger and a flat starter battery.
• The input side carries more than 18 A. The output is 18 A at a higher voltage than the input, through an 87 % efficient stage, so budget the starter-side cable, fuse and alternator for more than the nameplate current.
• VictronConnect shows no charge current. The Orion-Tr Smart range has no current sensor and no VE.Direct port, a limitation the non-isolated datasheet prints as a note. A shunt on the house bank is how you see the amps.
• Pick the battery preset before the first charge. Lithium profiles use a fixed two-hour absorption; the lead-acid algorithm adapts absorption to the depth of discharge. A fixed-voltage power-supply mode also exists and is not a charging profile.

• The most common thread is a smart alternator stopping the charge. Owners describe "input voltage lock-out, engine shutdown detected" whenever the vehicle battery is full and the alternator throttles back; the accepted fix is the ignition or D+ feed to the remote connector rather than lowering the thresholds. See this Victron Community thread and a MotorhomeFun discussion of the same symptom.
• Fuse questions come up constantly. The repeated answer in the 12/12-18 fuse and wire gauge thread and the fusing thread is that the fuse is sized to the cable, sits at each battery, and exists to protect the cable rather than the charger.
• Heat complaints centre on the 30 A model. The 18 A unit runs the same design at lower power, and the overheating threads (one example) are a reminder to give it airflow rather than a closed locker.
• Since 2024 the Orion XS is the usual recommendation for new builds where isolation is not needed: installers cite its higher efficiency, smaller size and current display in comparisons like this one. The isolated Orion-Tr Smart keeps its place where the two banks must not share a negative.

• Size the run with the wire size calculator and check the vehicle side with the DC-DC charger size tool, which separates output rating from input draw.
• Compare the Orion XS 12/12-50A if isolation is not a requirement, or the Orion-Tr Smart 12/12-30 for a larger house bank.
• Add a SmartShunt 500A or BMV-712 Smart to see the charge current the Orion cannot show.
• Open a complete dual-battery B2B example or the campervan solar and alternator diagram; each opens in Crimp.