Which end of circuit to add fuse. Battery, Charger or Both

[RaymondR]

Recently had an electrical fire whilst using a temporary electrical hook up and am now going to fuse everything at both ends, both positive and negative and each sub circuit. I used to have a steel boat and could afford to be a bit careless, electrical fires in FG boats are scary.

The shorted wiring melted it's way through other wiring and shorted it out thereby extending the fire and damage.

[s/v Jedi]

Originally Posted by gpsatsea

Thanks Jedi but I have studied that great diagram and used it effectively. However, it does not show a fuse coming out of the charger. Maybe because that charger has an internal fuse on the output already
I need to check my new Pronautic
Thanks.

Ah you are wondering why it needs to go at the battery end and/or why not a fuse at the charger end (the diagram is correct but does not show values for wire size, fuse ratings etc.) I can explain that:

As some already wrote, the fuses protect the wiring, not the equipment nor the batteries. So you take max. Amperage, length of run and acceptable voltage drop and come to a wire gauge to be used. You fuse at the ampacity of that particular wire, at the end where a current greater than that can come from. When you wire up an automatic charging relay that parallels two battery banks, there need to be two fuses, one at each battery bank. For a battery charger, it can not deliver a current greater than the ampacity of the wiring so needs no fuse.

When gear needs protection against over-current, it needs to be added to this, like a BMS with solenoid relay or MOSFET relay or a simple glass fuse in a radio power lead etc. A charger has current limiting technology built right in.