Product Profile
The BSB C7-50A is a fully sealed 50A DC contactor designed for medium-power switching in electric vehicles (EV), energy storage systems (ESS), and DC fast-charging equipment. It adopts an epoxy resin encapsulation that provides excellent resistance to dust, moisture, and oxidation. With a maximum switching current of 500A and non-polar design, the C7-50A offers reliable and safe operation in harsh conditions. It complies with UL, CE, and TUV standards, and supports horizontal or vertical mounting.
Product Features
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Epoxy-Sealed Housing: Fully sealed structure ensures stable performance in explosive or corrosive environments.
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High Current Handling: Rated for 50A continuous and 500A max switching at 320VDC.
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Non-Polarity Design: Simplifies wiring and reduces installation errors.
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Optional Energy-Saving Coil: Reduces holding power to 1.6W with built-in economizer.
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Robust Environmental Tolerance: Operates in -40°C to +85°C with IP67 protection.
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Compliance: RoHS certified, UL/CE/TUV approved.
Typical Applications
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Main relay in mid-range EV battery systems
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Battery switching in energy storage units
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DC quick-charging infrastructure
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Photovoltaic power switching
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Mobile robotics and AGVs
Summary of Technical Parameters
| Parameter | Value |
|---|---|
| Rated Current | 50A |
| Rated Voltage | 12–1000VDC |
| Main Contact Type | SPST-NO (1SH) |
| Contact Resistance | ≤2 mΩ |
| Max Switching Current | 500A @ 320VDC |
| Dielectric Strength | AC 3000V |
| Insulation Resistance | ≥1000 MΩ @ 1000VDC |
| Mechanical Life | 300,000 cycles |
| Capacitive Load Life | 130A (RC=1ms), 50,000 cycles |
| Operating Temperature | -40°C to +85°C |
| Coil Voltage Options | 12V / 24V / 12–24VDC (Energy-saving) |
| Mounting Orientation | Vertical / Horizontal |
| Auxiliary Contact (Optional) | NO / NC / None |
| Weight | ~190g–210g depending on version |
| IP Rating | IP67 |
| External Conductor Area | ≥10 mm² |
Dimensional Drawing & Wiring Diagram
Vertical type without economizer
Horizontal type without economizer
Vertical type with economizer
Frequently Asked Questions (FAQs) About The C7-50A DC Contactor
Q1: Does the C7-50A DC contactor have reverse surge protection?
A1: Yes, models with an economizer include a built-in surge suppression circuit. For models without an economizer, we recommend using a varistor or a TVS diode.
Q2: Can this contactor be used without a pre-charge circuit?
A2: For capacitive loads, a pre-charge path is required. Without it, high inrush current may cause the contacts to weld.
Q3: What is the recommended wire cross-sectional area?
A3: The external wiring should be at least 10mm².
Q4: Looking for a more compact 50A DC contactor from the C7-50?
A4: Yes. The C7 series does include a more compact 50A contactor with UL certification (compared to this model). To avoid confusion with the standard C7-50 product, it will be sold under a special product code. If you’re looking for a smaller-sized C7 series contactor that is not listed on the website, please contact the BSB sales team and mention that you need “the most compact C7-50 contactor.”
Q5: Besides the C7 series, what other DC contactors are available?
A5: In addition to the epoxy-sealed DC contactors of the C7 series, BSB also offers DC contactors with other sealing types. Please refer to the full DC contactors category section on the official website or contact the BSB sales team for more information.
Precautions for Use
To ensure safe and reliable operation of the C7-50A high voltage DC contactor, please follow the precautions below during installation and use:
Mechanical Installation
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Always use spring washers when installing to prevent screw loosening.
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Tighten installation screws with a torque of 3–4 N·m. Excessive torque may damage the contactor casing.
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Do not reuse the contactor if it has been dropped or impacted, even if no visible damage is found.
Polarity and Wiring
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The main contacts and control coil leads are non-polar, allowing flexible wiring.
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Ensure the external terminal has reliable contact with the contactor leads.
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Do not allow foreign substances or grease to accumulate on terminals, as this may cause overheating.
Surge Suppression (Coil Protection)
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For models with economizer, a built-in reverse surge absorption circuit is included—no external protector needed.
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For models without economizer, install a TVS or varistor at the coil terminals, rated at 1.5–2× the coil voltage.
⚠️ Avoid using diodes as they may reduce the breaking capacity.
Environmental Conditions
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Avoid installation near strong magnetic fields (e.g., transformers, magnets) or heat-radiating components (e.g., fuses, shunts).
If installation is unavoidable, perform a temperature rise test to ensure safety. -
Ambient operating temperature: –40°C to +85°C
The product is gas-filled and sealed. Excessive temperature will accelerate internal gas diffusion and shorten lifespan. -
Altitude limit: ≤4000m
Switching Performance and Life
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This contactor is a high-voltage DC switching device with a defined service life.
Do not use it beyond its rated switching capacity or life expectancy. -
In the event of failure (e.g., contact sticking), ensure your circuit design can cut power within 1 second.
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For resistive loads, apply the rated values directly.
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For inductive loads (L/R > 1 ms), a parallel inrush current protection device (such as TVS) must be installed.
Coil Drive Requirements
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If the coil and main circuit are operated continuously at rated voltage and immediately reclosed after disconnection, the coil temperature will rise, increasing resistance and closing voltage.
If this causes operation issues, apply the following measures:
– Reduce load current
– Limit continuous ON duration
– Use slightly higher-than-rated coil voltage -
For energy-saving models, the economizer activates ~0.1s after power-on. Do not cycle the contactor at that moment—it may cause internal failure.
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The coil drive voltage and current must meet inrush and holding requirements. Undersized power sources may reduce the contactor’s cut-off ability.