BF1 Fuse

BF1 fuse – compact MIDI-class bolt-down fuse by Littelfuse for commercial vehicle electrical systems

The BF1 fuse by Littelfuse is a compact bolt-down fuse of the MIDI class, used in truck and commercial vehicle electrical systems primarily in the lower high-current segment. With its screw-fixed design, it represents a protection solution within the Littelfuse family that can be mounted directly at the consumer. At SULEJ Ladebordwand you will find the BF1 fuse as robust protection for individual supply paths, control-unit feed lines and smaller auxiliary units where a securely seated bolt-down connection is required.

Design and electrical layout of the BF1 series

A characteristic feature of the BF1 fuse is a stocky PPA thermoplastic housing with two closely spaced bolt terminals, through which the fuse element is screwed directly onto a carrier rail or distribution block. The series is rated for 58 V electrical system voltage (also available in 32 V) and covers a typical current range of approximately 40 to 200 A, with the 150 A and 200 A ratings intended for short-circuit protection only. The tripping characteristic is Slo-Blo® time-delayed and follows ISO 8820-5:2015. The breaking capacity is 2000 A and the permitted operating temperature ranges from -40 °C to +125 °C. A transparent cover and a clear colour coding make optical condition checks and current rating identification straightforward.

Use in the secondary circuit and selecting the right BF1

The BF1 fuse is typically used in branches from the main current circuit – for example as a pre-fuse for control modules, auxiliary pumps or individual supply lines directly at the consumer. Key selection criteria are nominal current (typically 40–200 A), electrical system voltage (32 V or 58 V) and the bolt centre distance to the existing fuse base. Clean tightening with a defined torque is important, since loosened bolt contacts can show up under vibration in the form of increased contact resistance.

Benefits at a glance

• Compact bolt-down housing made of PPA thermoplastic for direct mounting on the distribution block
• MIDI class: typical current range approx. 40–200 A, electrical system voltages 32 V / 58 V
• Slo-Blo® time-delayed tripping per ISO 8820-5:2015
• Breaking capacity 2000 A, operating temperature -40 °C to +125 °C
• Transparent cover and colour coding for clear identification

A correctly sized BF1 fuse protects individual consumers precisely and effectively complements larger main fuses within the electrical system.