By now Im sure you are knee deep in diapers. I hope all is well. As for me, well I have been better. Today, I was getting the boat ready for fishing this week and unfortunately, it caught fire. I haven’t been out since you worked on it so Im not sure what to do moving forward. Can you make some time to come look at it and possibly figure this out. I can explain all the steps I took prior to the fire when we speak. Hope to hear from you soon.
Dave (name changed)
Gulp. I emailed him back and was there bright and early the next morning, ready to confront an awkward situation. The boat was not burned. The only thing that caught fire and burned was the alternator. Whew. I asked him about this, and why he didn’t say it was just the alternator, so as not to give me a heart attack. Email is dangerous.
It turned out he’d bought a new battery for his two bank system, which has a standard 1-2-both-off battery switch, only he connected the battery backward, with the positive to the negative and the negative to the positive. He then turned the battery switch to the #1 position and the alternator burst into flames.
After doing some deconstructing and poking around, I figured he was very lucky it was only the alternator (about $300 to replace).
By doing what he did, he’d reversed the polarity on his system, making for a positive ground. For many things aboard, like lights, this wouldn’t make a difference. For other things, like electronics and the alternator, it would make a catastrophic difference. When he turned on the battery switch it created a dead short somewhere in the alternator and up it went!
If he’d try to start the engine, something very bad would have happened to the starter, and maybe the engine.
AND, by reversing the connections on Battery 1, he would have inadvertently wired Battery 1 and Battery 2 in series, creating a 24-volt battery. Had he turned the battery switch to the “Both” position he would have created a dead short, at 24 volts, at the battery switch. The battery switch was rated to 300 Amps or more, so the fireworks would have lasted a while before the battery switch finally melted down…in flames. Of course there were no high capacity fuses anywhere in the system.
I’ve spent twenty minutes drawing diagrams and trying to figure out all the implications of such an error. There are many and it gets confusing, so probably best we just connect batteries with the proper polarity.