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SMARTPASS 120S (1058)

CTEK SMARTPASS 120S connections

Review the CTEK SMARTPASS 120S connections, setup and installation requirements. This overview does not calculate cable or protection sizes.

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Nominal voltage
12 V
Compatible systems
12 V
Units

Connection overview

SMARTPASS 120S connections.

See how this component fits into a system. Use the manufacturer’s installation instructions for the complete connections.

CTEK SMARTPASS 120S connection overview with 4 components: SMARTPASS 120S, 12 V starter battery, 12 V service battery, Noncritical house circuits. 5 cable connections. Crossings are not junctions.12 V starter battery + to SMARTPASS 120S ALTERNATOR +. SMARTPASS 120S SERVICE + to 12 V service battery +. SMARTPASS 120S CONSUMERS + to Noncritical house circuits +: 300 A specified fuse. 12 V starter battery − to 12 V service battery −. 12 V service battery − to Noncritical house circuits −12 V starter battery + to SMARTPASS 120S ALTERNATOR +SMARTPASS 120S SERVICE + to 12 V service battery +SMARTPASS 120S CONSUMERS + to Noncritical house circuits +: 300 A fuse12 V starter battery − to 12 V service battery −12 V service battery − to Noncritical house circuits −CTEK SMARTPASS 120S. 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. Connection overview only. Cable lengths are placeholders; use the complete manufacturer diagram to select conductors and protection. No automatic fuse or cable-size recommendation is supplied by this example. CTEK manual p5 specifies 35 mm² minimum and 300 A protection through 2 m. These 1 m examples use 70 mm² to also support the fuse in Crimp's conservative marine ampacity table; verify the installed cable and M8 lug fit (maximum 6 mm lug thickness). Supply the omitted negative/control/temperature leads using the full manual. Consumer branch protection inside the downstream distribution remains separately selected.SMARTPASS 120SALTERNATOR +ALTERNATOR +SERVICE +CONSUMERS +12 V starter battery. CTEK specifies 300 A battery-end protection. An MRBF holder/fuse is the illustrative 12 V implementation; verify exact product, terminal mounting and interrupt capacity against actual battery fault current.12 V starter battery300 A MRBF at battery +++−−12 V service battery. CTEK specifies 300 A battery-end protection. An MRBF holder/fuse is the illustrative 12 V implementation; verify exact product, terminal mounting and interrupt capacity against actual battery fault current.12 V service battery300 A MRBF at battery +++−−Noncritical house circuits. Consumers represented as their protected distribution circuits. Critical loads must bypass SMARTPASS consumer disconnection. Establish total demand before sizing.Noncritical housecircuits++−−300 A fuse
CTEK SMARTPASS 120S connection overview with 4 components: SMARTPASS 120S, 12 V starter battery, 12 V service battery, Noncritical house circuits. 5 cable connections. Crossings are not junctions.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. Connection overview only. Cable lengths are placeholders; use the complete manufacturer diagram to select conductors and protection. No automatic fuse or cable-size recommendation is supplied by this example.
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Installation notes

Before you install.

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Verified against the manufacturer's documentation (rev. D250SE / SMARTPASS 120S UK English manual; model 1058), checked 2026-10-01. Manufacturer documentation →

What is SMARTPASS managing?

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.

How are the three power connections used?

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.

What protection and mounting are specified?

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.

How does operation change?

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.

Fit check

Connect it to the rest of your system.

Describe your setup to draft a system with SMARTPASS 120S (1058) connected. Review the selected parts and cable lengths, then edit the diagram in Crimp.

The model only picks parts and draws the connections. Every wire size and fuse rating still comes from Crimp's own sizing, never from the model.

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Technical reference

Specifications and terminal map.

Check the model, ratings and connection points against your own unit before choosing installation hardware.

Catalog specification

Alternator-to-house-battery power-management unit with a 120A battery path and separate 80A consumer output. It connects batteries under defined conditions; it is not a regulated DC-DC charger. Critical loads bypass its low-voltage consumer disconnect. Small negative/ignition/sensor wires are omitted from this power-path symbol.

Nominal voltage
12 V
Compatible systems
12 V

Terminal map

Catalog connection points, current direction and planning limits. Check the manufacturer's pinout and connector ratings before installation.

ALTERNATOR +

positive · input

120 A

SERVICE +

positive · bidi

120 A

CONSUMERS +

positive · output

80 A
Sources and sizing method

Equipment specifications. Model details, ratings and terminal roles come from the catalog. Check your unit’s label and current manufacturer documentation for its exact revision.

Connection overview. This diagram explains the connection arrangement; it does not calculate cable sizes or protection for the installation. Follow the manufacturer’s complete wiring and protection instructions.

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Next step

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