
What Size Circuit Breaker Should I Select for My Car Battery Configuration?Consider the total load amperage of your devices.Assess the wire gauge to determine the appropriate breaker size.Use a breaker size that allows for a 25% margin above the total load.Evaluate the type of circuit breaker: automatic vs. manual reset.Examine the vehicle’s electrical system and compatibility with existing components. [pdf]
Round the breakers up to next common size and you have600A vs 500A. If the battery cabinet design is only for capacity (meaning all cabinets must be on line to handle discharge) one could use 500A breaker, maybe even 450A in the scenario above. Sometimes it is requested that 600A be used however.
The highest voltage that may be applied over all end ports, the distribution type, and how the circuit breaker is completely integrated into the system all contribute to the overall voltage rating. It is essential to choose a circuit breaker with sufficient voltage capacity that corresponds to the end application.
The standard rating of a DC circuit breaker is 700A. The battery short-circuit current, per published data for the battery=14,750A. Therefore, the recommended circuit breaker in this example=700A, 65VDC, 15,000 AIC. Moving onto the conductor, we know the cable sizing current=1.25×533=666A.
Circuit Breaker Size: ? CB size should be rated at 125% of the circuit current. = 125% × 16 A = 1.25 × 16 A Required Circuit Breaker Size = 20A NEC 210.19 for continuous load circuits (Article 100) suggests that a 20-amp breaker should be used at 80% of its rated load for continuous circuits.
The battery circuit breaker sizing current = 1.25 x charging current = 1.25 × 400A =500A. The standard rating of DC circuit breaker is 500A. Therefore, the recommended circuit breaker in this example=500A, 65VDC, 10,000 AIC. Moving on to the conductor, we know the cable sizing current=1.25×400A=500A.
Circuit breakers are available in a variety of sizes and configurations. The highest voltage that may be applied over all end ports, the distribution type, and how the circuit breaker is completely integrated into the system all contribute to the overall voltage rating.
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