My fuse holder melted, making my dc to dc battery charger unable to charge my auxiliary battery. However, the fuse has not blown. Does this mean my equipment is faulty and drawing too much current?
If the fuse itself has not blown, but the fuse holder melted, it indicates that the fuse holder was making poor contact with the fuse. Loose connections are common with poor quality fuse holders. Because they don't make adequate contact with the fuse, they can allow dirt and dust to get in between the contact points - resulting in voltage drop.
Heating in an electrical circuit is always caused by current flowing through a resistance. If there is significant resistance in the contact between fuse and fuse holder, a current well below the fuse rating can cause enough heat to melt an inline fuse holder.
Note, this heating of the electrical fuse may not always be immediate. Whilst the initial resistance may be lower and the initial heating may not be enough to reach the fuse melting point, the heating can cause oxidation of the metal connections, leading to increased contact resistance.
This accelerates the heating effect until there is an “avalanche” of rapidly increasing heating/increasing resistance, leading to what may appear to be a sudden failure even some time after the installation.
The simple answer is: if the fuse holder melted, it is due to a lost connection, not the power wires drawing too much current.
When installing battery management systems and battery chargers, you always need to use good quality battery fuses and fuse holders. This will ensure the wires connected to your fuse holder make a solid connection, giving you peace of mind that your charger/power source is working efficiently.
Whilst the popular, automotive blade type fuses and holders may be okay at lower currents (e.g. 5-10A) and for higher currents (20A or more) it is essential to use good quality fuses and fuse holders. REDARC’s 40A Fuse Kit and 60A Fuse Kit are a great example.
Especially if you want your battery systems and dual battery isolators to keep functioning for years to come. Good examples include “Maxifuse”, “Megafuse” or “MTA” Midi fuse style products.