Fusing requirements for our products.
Required fuse sizes are specified in the relevant owners and/or installation manual. This document explains why fuses are required. It is not comprehensive. Fusing is an extremely involved subject and could easily take up an entire book.
Fusing of electrical and electronic equipment is required for 2 basic reasons. A. To comply with legal and/or safety requirements which exist because of the necessity to B. Prevent overheating cables and/or fires in the event of a fault.
Assume a 2.5mm cable used to power a load from a 200 amp hour battery bank. If these cables become short circuited, the current that will flow as a result will, of course, cause immediate overheating of the cables, melting of the insulation, possible further short circuits with other cables and could finally start a fire. Not to mention the mess it will make of the installation.
A fuse is a deliberate "weak spot" put in the system so that the weak spot blows instead of the cabling. It is obvious therefore that the fuse must be rated so that it will blow before the cable is damaged. There must be a substantial margin between the rating of the fuse and the rating of the cable. For instance a cable of 2.5mm is generally rated to carry 30 amps. A fuse with a rating less than this must be used. There is little point fitting a 60 amp fuse in a 30 amp cable as the cable will blow first.
It is often thought that fuses are there to prevent further damage to electronic equipment in the event of a fault. This is totally incorrect. Electronic components act, to all intents and purposes, instantly. This also means that in the event of a gross fault, they fail instantly. A fuse takes somewhat longer. A fuse simply will not protect electronic equipment. By the time the fuse blows, the damage to the electronic compenents is already done.
So now we have clarified what a fuse is actually for i.e. to protect the cabling, it becomes clear why the fuses should be as close to the batteries as possible. There is little point in having a fuse at the end of a 10 metre cable if the short circuit happens 2 metres from the batteries.
SmartBank, SmartGauge and SmartGuard should be fused at 3 amps.
Fuses should never be put in the battery compartment unless the batteries are certified as being suitable for use in habitable spaces. Which means they will not give off explosive gasses during charging. Generally this means gel batteries and AGM batteries only. All other types give off explosive gasses during normal charging.