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The CTEK SMARTPASS 120S is a high-capacity 12V power management solution designed for dual-battery systems in vans, motorhomes, 4x4s, boats, and other vehicles requiring reliable auxiliary battery charging and power distribution.
The SMARTPASS 120S manages up to 120 amps continuously, directing available alternator power to the service battery and connected electrical equipment. Its intelligent Battery Guard system prioritizes critical electrical loads while protecting the auxiliary battery from excessive discharge.
The SMARTPASS 120S can also be integrated with the CTEK D250SE 20A onboard charger to create a combined 140A power management and charging system.
| Specification | Details |
|---|---|
| Brand | CTEK |
| Model | SMARTPASS 120S |
| Part Number | 40-678 |
| Previous Article Number | 40-289 |
| System Voltage | 12V |
| Charging Category | DC Charging |
| Input | 11.5–23V |
| Continuous Input Current | 120A |
| Maximum Temporary Input | 350A for 10 seconds |
| Continuous Output | 120A |
| Maximum Temporary Output | 350A for 10 seconds |
| Battery Capacity | 28–800Ah |
| Battery Chemistry | Lead Acid / Lithium-Ion |
| Compatible Battery Types | WET, MF, Ca/Ca, AGM, EFB, GEL, LiFePO₄ |
| Power Source | 12V → 12V |
| Protection Rating | IP65 |
| Operating Temperature | -4°F to +122°F (-20°C to +50°C) |
| Back Current Drain | Less than 7Ah/month |
| Dimensions | 7.6 × 4.3 × 2.6 in |
| Net Weight | 1.09 lbs |
| Warranty | 2 Years |
The SMARTPASS 120S uses an integrated Battery Guard system to help prevent the service battery from being completely discharged.
When auxiliary-battery voltage becomes low, the system can disconnect non-critical electrical loads while maintaining power to priority equipment. This is particularly useful for vehicles carrying important electrical equipment such as radios, emergency lighting, navigation systems, refrigeration, and other auxiliary loads.
The SMARTPASS 120S allows available alternator power to be intelligently distributed between the auxiliary battery and connected electrical consumers.
It provides up to 120A of continuous power, with dynamic over-current protection capable of handling temporary loads up to 350A for 10 seconds.
The SMARTPASS 120S is designed to work with the CTEK D250SE 20A DC-DC charger.
When combined, the system can provide up to 140A of power management, making it an excellent solution for larger auxiliary electrical systems in motorhomes, vans, 4x4s, and overlanding vehicles.
The SMARTPASS 120S supports a wide range of 12V battery technologies, including:
It supports both lead-acid and lithium-ion battery chemistries with service batteries ranging from 28–800Ah.
Built-in battery temperature protection reduces charging current when battery temperature becomes excessive. This helps protect the service battery and charging system during demanding operating conditions.
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