Dear Boat Doctor,

I’d like to install some USB ports to charge phones and tablets on my boat. I have a J/35 built in 1986, so the entire interior has exactly one 12-volt receptacle built into the electrical panel next to the starboard quarterberth. I’m OK with that, but my kids seem to run their iPods all the time, so I need a way to charge them without fighting over the single receptacle. My thought was to install two USB ports, one going forward to the V-berth and one over to the port quarter berth. How do I connect them to the electrical system?

Rich Evans

Minneapolis, Minnesota

Dear Rich,

You’re facing what’s becoming a more common problem for boat owners. USB has become the ubiquitous charging port, especially for personal entertainment devices. 

The Blue Sea 1016 from Blue Sea Systems (www.bluesea.com) is a two-port charging socket that should work well for you. USB draws a maximum of  2.1 amps, so you’ll need to design the electrical system around this.

You’ll need a 2-amp fuse to protect the circuit; a Blue Sea 5064 holder with a Blue Sea 5236 2 amp ATC fuse is perfect. You’ll also need a fuse and holder for each socket. If it’s convenient you can place the fuse right behind the socket or alternatively at your panel.

To figure out your wiring requirements, consider that you will be carrying 2 amps to and from the V-berth, a distance I would estimate to be a round trip of 40 feet. I estimate roughly 20 feet to supply current to the socket and the same distance for the return. The distance and current dictate 16-gauge wire and I’d use Ancor (www.ancorproducts.com) 16/2 AWG duplex cable.

You have some choices in how you feed these sockets. If you have a spare breaker in your panel, you could feed from that. Just connect the red wire to the breaker and the black wire to the negative bus in the panel. If you don’t have a spare, you can feed from the same source as the existing 12-volt receptacle.

USB ports draw a tiny bit of current even with nothing plugged into them. I have experimented with a few and seen a 15 milliamps draw. This is a pretty small amount of current, but could make a difference depending on how you use your boat. If the boat is plugged in most of the time you’ll have no problem, but if not, this current draw will add up. You can solve this problem with a switch in the supply line, or by feeding the sockets from a breaker that you only turn on when needed. If you’d like to place a switch right at the charging socket, check out the Blue Sea 4353 Belowdeck panel. This gives you a switch/breaker, 12-volt socket and dual USB in one small little panel.