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A fuse "blows" if current greater than fuse's rating flows through. But recently I was connecting battery terminals opposite on a motorbike; this kept blowing the fuse. When I correctly connected the terminals, the new fuse did not blow.

Shouldn't the current that passes through be same regardless of connection?

Not sure if this is right place to post. Any info greatly appreciated

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The current depends on the polarity, if the circuit contains components that behave differently, such as diodes, which only conduct the current one way. Perhaps the fuse that was blowing was there on purpose to protect the sensitive engine control electronics from an accidentally wrong polarity.

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I have found it online: http://www.sto-p.com/pfp/pfp-reversepolarity.htm

Essentially a reverse biased diode sourced to ground lies in the same circuit in parallel. When polarity is reversed, the diode conducts and shorts the power supply, thereby blowing the fuse.

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  • $\begingroup$ Sounds like a "crowbar." That's a term of art in electronics design for a circuit that forces a fuse to blow or a circuit breaker to trip if something goes wrong. In the case of your diode, it protects the electronics on your bike from being connected to reverse-polarity power. The name is supposed to conjure up an image of using an iron crowbar to short out the power supply. $\endgroup$
    – Solomon Slow
    Commented Sep 28, 2017 at 13:47
  • $\begingroup$ This is exactly 100% the same as what I said in my answer. $\endgroup$
    – safesphere
    Commented Sep 29, 2017 at 3:16

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