I'm working on my camper's solar system with a 200W solar panel (solar bag) that has a Voc of 23.9V and an Isc of about 10A. I have a couple of questions regarding the need for fuses in my setup. First, should I install a fuse between the solar panel and my MPPT (100|20) controller? The cable connecting them is 5 meters long and 6mm2. Secondly, my camper's EBL (power distribution unit) already has a built-in 15A fuse for the solar input; do I still need a separate 15A fuse in the 1 meter long 4mm2 cable from the MPPT to the EBL?
5 Answers
Absolutely! You should fuse close to any generation or storage device for extra protection. It’s a good practice even if your current is low.
You don’t need to worry about fuses in this setup. Your 6mm2 wire can handle 30A, and the MPPT can handle up to 20A, while your panel only puts out about 10A. Since that's the max, a 30A or even a 20A fuse wouldn’t trip, while a 10A fuse might be too close to the edge on colder days. So, no fuses are necessary between the panel and the MPPT. For the cable from the MPPT to the EBL, since there's already a 15A fuse in the EBL, you're safe there as well. You can add fuses if you want, but they're not required.
It's wise to err on the side of caution and add fuses wherever possible. Better to be safe than sorry!
I think having a fuse between the solar panel and the MPPT isn’t really needed since the panel usually doesn’t produce more current than rated. But it's smart to have some kind of disconnect switch for safety. I use a combiner box with a master breaker and fused breakers for each string. It gives me peace of mind, especially with grounding for any lightning strikes.
Definitely include a circuit breaker between your solar panel and MPPT/inverter! It functions like a fuse and allows for easy disconnections if needed.
That makes sense! Just keep in mind you might want fuses if you add more panels in parallel.