Now what was that electrical formula?
Yesterday was Grenadian Thanksgiving and given that almost all of the stores on the island were closed for the holiday, including the boat chandleries, it was not an ideal time to attempt to repair our non-functioning solar system. In spite of that, I still took some steps to revive it.
Non-functioning, you say? Yes. Late Wednesday afternoon, after returning from our jog around Fort Jeudy, I took note of the fact that our battery voltage was down a bit. This was in spite of the fact that the remote display for our solar charger was indicating that we had beaucoup amps coming in from the panels. Having danced this dance before, I went immediately to the fuse in the circuit to see if that was the culprit. Sure enough, not only had the 15 amp fuse burned out but the rubber case that held it was melted and charred. Not good. I should point out as well that, this is not the first time that this fuse has blown and the previous time it did so, I had to replace the fuse holder then too!
Charred and melted fuse holder — rated 15 amp max.
Why would this happen? That particular piece of the circuit was wired at a time when the boat only held 150 watts of solar panels. If I can remember my basic electrical theory, P=EI. This means that 150 watts divided by 12 volts equals 12.5 amps. Given that, a 15 amp fuse would be perfect.
When we added the additional 135 watt panel though, we upgraded the solar charger but never did anything about that fuse. The same electrical formula above shows that, now having 285 watts of solar, the circuit should be sized for 23.75 amps. No wonder the fuse blew!
16 amps coming in. Gee, I wonder why that 15A fuse blew?
Rhetorical question — don’t feel compelled to answer.
Given that the stores were closed, I couldn’t very well go shopping for a new fuse holder. I did check out the catalogues though and picked out a beefy Blue Sky one that I intend to use when I get my hands on one, which hopefully will be today. In the meantime, I simply jumped the fuse out, after increasing the size of the wire in that short run (that’s how I was able to get the above photo).
Yeah, yeah… I understand about the issues of jumping out the fuse so no lectures please. I promise not to leave the solar circuit live unless I’m on the boat monitoring it.