Years of experience with DIY solutions to "improve" perfectly good working systems.
Ah I see. I'm sorry you've bad such bad DIY experiences. I've had mostly good ones. It does often take a few revisions to perfect, but that doesn't bother me. Besides, I enjoy the troubleshooting and learning process--it's one of my hobbies.
I understand that on land or in a car, the 2.5-4W watts consumed by a relay is moot. On a 30ft sailboat with finite solar capacity, though, it can make a massive difference. Solar panels are often damaged by storms or rogue waves. The sails cast shadows on the solar panels for parts of the day. Consecutive cloudy days can also happen. Solar capacity can easily be halved or totally destroyed, leaving only the house batteries. Although I'll try to fit a solar array of ~300W, I'm trying my best to stay around 100 watt-hours per day of consumption.
So, the 2.5W-4W (per device) really can make a big difference. It can mean the difference between being able to activate AIS or not. When I'm 1500km from the nearest coastline, in pure darkness or a storm where I cannot see over the crest of the next wave, AIS can tell me whether or not there are cargo ships within a 10km radius, and what our closest point of approach will be. That same AIS can also allow me to sleep for 20 minutes at a time. It's pretty important stuff.
I appreciate your input. For my purposes, I really don't see the downside. It's a drop-in, plug-and-play replacement module for an automotive relay. If it causes me trouble, it's a matter of putting the original automotive relay back in. As I see it, I can benefit greatly at zero risk.
Certainly we can disagree on whether this circuit is necessary/useful, but that's just a matter of opinion/preference. On the other hand, if you truly anticipate functional problems with this circuit, please share your concerns so that I can find a solution to them.
Cheers
