Fuse size from charge controller to battery

Re: Fuse size from charge controller to battery

Fuses are there to protect the wiring... So, if you have (for example) a 14 AWG wire from the battery to the charge controller, then you would use a 15 amp fuse maximum.

Every wire that leaves the battery should have its own fuse/breaker sized to the wiring/loads.

Note that a 40 watt panel has an Imp rating of around 2.3 amps-- A 5 amp minimum fuse/wiring should be fine. Having short/heavy wire from the charge controller to the battery bank is good. You want low voltage drop (0.05 to 0.10 volt drop recommended maximum). Long/thin wires from the charge controller to the battery bank with high voltage drop can reduce charging performance significantly.

Note that for fusing/wiring, you should only run 80% of rated current for you can pop the fuse/breaker. A 15 amp circuit * 0.80 = 12 amps maximum continuous current.

Using the "Load" terminals on the charge controller is frequently not very useful. They are usually current limited (sometimes as low as 8-10 amps) and the "cutoff" voltage is typically quite low (10.5 volts or so)--At that voltage level, most batteries will be damaged and severely limiting their life.

Your 40 watt panel and two deep cycle batteries (depending on the size of the battery bank -- AH @ what voltage) is not very large... That would typically be used to "maintain" the batteries (float them when the trailer is in storage).

For most people, they would make use of a larger panel (one or two 140 watt panels). Especially if you go for days/weeks of dry camping at a time.

-Bill

Re: Fuse size from charge controller to battery

12.5 volts is pretty high--You could probably set that to 12.0 or even 11.5 volts (especially for "heavier loads") and still be OK.

In the end, if the system is working well for your needs--Then why not continue.

-Bill