SMARTPASS 120S (1058)
Review how the CTEK SMARTPASS 120S connects, how it operates and which installation requirements apply to this model.
Open this example as a new project. Use your own parts and cable lengths to make the plan yours.
The SMARTPASS switches charging and consumer paths between two batteries. Review its operating states, battery protection and the complete CTEK wiring diagram before connecting it. A contact rating does not establish a cable's operating current.
The SMARTPASS switches charging and consumer paths between two batteries. Review its operating states, battery protection and the complete CTEK wiring diagram before connecting it. A contact rating does not establish a cable's operating current.
Wiring diagram
Open this example in Crimp to use your own parts and cable lengths. Review the assumptions and installation notes as you adapt the circuit.
Installation notes
Guidance for this model, with sources linked beside the relevant advice.
Verified against the manufacturer's documentation (rev. D250SE / SMARTPASS 120S UK English manual; model 1058), checked 2026-10-01. Manufacturer documentation →
The SMARTPASS 120S connects an alternator/start-battery supply to the service bank under defined operating conditions. The battery path is rated 120 A continuous; the consumer output has a separate 80 A limit. It is a battery-management connection device, not a regulated 120 A DC-DC converter.
Wire ALTERNATOR + to the starter side, SERVICE + to the house battery and CONSUMERS + to noncritical loads. Its small negative, ignition and temperature-sensor wires must also be fitted. The manual directs critical loads to the service battery through their own protection, so its low-voltage disconnect cannot disable them.
The cable table gives 300 A fuses and 35 mm² battery/output conductors for runs through 2 m; longer input runs need the stated 50 mm² arrangement. Those fuses accommodate transient operation and are not a claim of 300 A continuous charging. Main connections tighten to 8 Nm. Install with ventilation and the temperature probe at the service battery.
With the engine stopped, consumers use the service battery. With alternator power available, source priority can power consumers while charging the bank. The consumer guard disconnects at low service voltage; automatic start assistance can temporarily join the batteries. Check the indicator pattern and matching manual before resetting a reported fault. When adding a D250SE, use the documented combined layout and verify alternator and battery current limits independently.
Build it out
Add SMARTPASS 120S (1058) to your diagram, then connect your batteries, chargers and loads. Crimp calculates cable sizes and checks the connections as you draw.
Every cable you draw there is sized against ABYC E-11, from the same tables as the reference on this page.
Technical reference
Check the model, ratings and connection points against your own unit before choosing installation hardware.
Check stud sizes, fuse type, run length and how warm the space gets against the gear you actually have before you order.
Catalog connection points, current direction and planning limits. Check the manufacturer's pinout and connector ratings before installation.
ALTERNATOR +
alt-pos
positive · input
SERVICE +
service-pos
positive · bidi
CONSUMERS +
consumer-pos
positive · output
Method & provenance
Manufacturer specifications describe the equipment. Crimp calculates cable results from the circuit and assumptions you enter.
From the maker
Manufacturer, model, ratings and which terminal does what come from the catalog. A newer revision, or the nameplate on the unit in your hand, can say something different — when it does, the nameplate wins.
ABYC E-11
Sized against ABYC E-11. Boats built to UK or EU rules answer to ISO 13297 — check these figures against it before you build. The run length and the current above are what drive the result. Crimp doesn't know how warm your space gets; draw the cable inside an engine-bay zone on the canvas and it sizes for the heat.
Next step
Open this example as a new project. Add your equipment and cable lengths, then review the sizing and checks for your setup.