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I made a battery charger last year - I put the fuse in the positive lead. Electrically speaking, it doesn't really matter whether the fuse is in the postive or negative. Putting it in the positive is only a convention, and electron theory is not of any importance in this matter.
However, when we start thinking about the mains circuits, in our house, it is important that ONLY active (hot) cables are fused. If a neutral had a fuse in it, and that fuse blew, one side of the fuse would become live. This creates a safety hazard, if someone touches the fuse terminals. Getting electrocuted is NOT a good thing!!!! :twisted:
Thanks for replies, i am aware that a mains fuse/sw are connected inline, i am about to build an automatic car battery charger but intend to fit a 20mm 5A fuse from Tx secondary to the ac side of the bridge of course,. if i was going to insert a fuse inline with the o/p leads i too would automatically put it in the pos/lead as a matter of course. :shock:
Always connect positve first then negative for chargers and jumper cables [I guess they're chargers too]. The huge amount of 'ground' is too easy to short to. Fuse in the negative would follow this safety rule. Saw a guy have a auto battery explode in his face once when his hand slipped.