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I have just purchased an Smart Solar charge controller MPPT 100/30. I am a little confused as to whether I need to put a fuse between the controller and the battery, as there is an internal [but non replaceable ] fuse in the controller. If so, should it be 30 amps.. Are any other fuses required in the setup eg between the panel and the controller?
The basic rule of thumb is all wires in a system should have their own circuit protection (either a fuse or circuit breaker).
The size of the fuse or circuit breaker should be ~80% the current carrying capacity of the wire that you use. The circuit protection should be appropriate to the application (eg High Rupture Current for DC inverter input), DC rated for MPPT, Residual Current Detection for AC loads, etc).
Internal fuses in Victron Equipment should NOT be relied on for circuit protection, they are for the protection of the device. You will need to supply and install external, appropriately sized and replaceable fuses for a safe installation.
Exact fuse requirements are regionally specific, eg in Australia, for solar panels you need double pole (positive and negative) isolation with active wire string fuses if the string exceeds the rated current capacity of the solar panel. This can get complicated for a whole system, so it is best to consult (and pay for) a suitably qualified local installer who will be familiar with the local requirements and have a ready supply of the suitable parts.
