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Old 06-05-2016, 09:21   #1
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USB jacks phantom loads

I'm rewiring my boat from scratch. I was thinking about putting USB outlets in 2 places in the cabin, under my hard dodger and in the v-berth. Tablets, phones, everything, you know.

Anyway. I was planning on wiring some USB outlets into my 12v cabin lighting breaker. But wondering if they have a phantom load and will be drawing power all the time? I suppose I could add switches to each of them but that seems to complicate things a bit.

Any thoughts?

Thanks
Paul
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Old 06-05-2016, 09:28   #2
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Re: USB jacks phantom loads

Short answer, since there is a power supply that converts your 12V to 5V for the USB there will be a parasitic power draw by the unloaded power supply.

Blue Sea at least lists that in their specifications (harder information to come by on e-bay/Amazon), their dual USB outlet has a parasitic draw of 15mA at 12V. That works out to about 1/3Ah/day, so you'll have to decide if it is worth a switch.
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Old 06-05-2016, 09:33   #3
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Re: USB jacks phantom loads

Thanks! My other alternative would be to install cigarette lighter outlets and put USB converters in them as needed. That would be a no-draw solution, yeah?
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Old 06-05-2016, 09:34   #4
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Re: USB jacks phantom loads

I do hate those outlets...
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Old 06-05-2016, 09:53   #5
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Re: USB jacks phantom loads

I have 5 double USB outlets onboard. Each one has a green LED light that is always on (when the breaker switch is on, of course) I don't know the draw of each one, but I figured it is so small that it's not worth worrying about.


Even if each USB draws 3 times what Dsanduril quoted, then it's costing me 5ah per day, nothing to lose sleep over. Although sometimes the led light on the USB in my cabin annoys me and causes me to lose sleep
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Old 06-05-2016, 10:00   #6
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Re: USB jacks phantom loads

I hate the 12V cigarette outlets as well, but yes, they do provide a zero draw solution (as well as allowing you to plug in things like laptop chargers, etc. that might not be USB powered).
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Old 07-05-2016, 08:55   #7
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Re: USB jacks phantom loads

One could install a switch to control the 12v. going to the USB receptacle, which would allow zero draw when not in use.
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Old 07-05-2016, 09:58   #8
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Re: USB jacks phantom loads

Blue Sea makes a panels with both the socket and dual USB outlets with a switch. Product number 4353. That looks like a great solution if you have the room.
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Old 07-05-2016, 10:29   #9
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Re: USB jacks phantom loads

USB. Add a switch for 79 cents and you're done. No big deal.
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Old 07-05-2016, 11:03   #10
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Re: USB jacks phantom loads

I put the plastic cigarette-lighter jacks all over our boat, then plugged in the USB converters. I measured the "parasitic drain" for them and found it was about 1.5 milliamps (no pilot lights on 'em) each, which equals .036 amp-hours per day (X 6 = .216 amp-hours/day).
These have worked 100% for me, other than one of the USB converters failed (I have several spares). Having the butt-lighter jacks has also been occasionally handy - for example I have a Ryobi 12V tool-battery charger that has a butt-lighter plug.
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Old 07-05-2016, 11:23   #11
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Re: USB jacks phantom loads

Quote:
Originally Posted by Lancerbye View Post
One could install a switch to control the 12v. going to the USB receptacle, which would allow zero draw when not in use.

That would be my choice. They don't draw a lot (although more than an LED, typically) and if you anticipate they would not all be in use at once, a five amp circuit breaker on your DC board marked "USB OUTLETS" would cover it.

I would hesitate to just wire them into the cabin lighting, even though that would save wire runs. It's easier to confine all charging in one spot (say, the nav station) and just have a couple of USB outlets there. Same for a DC/DC hardwire for your laptop, if applicable.
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Old 07-05-2016, 11:41   #12
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Re: USB jacks phantom loads

I installed a few USB jacks in our boat. (being super-cheap, I hacksawed dual USB jacks from old motherboards and epoxied them into square "flanges" for mounting).

To power them I put a LM2596-based 3 amp DC-DC step-down converter (all over ebay for like $2) in a box with a fuse and an LED. The quiescient current of the reg is allegedly around 5 mA, and the LED +resistor pulls about 5mA. At the moment I've connected all this to the lighting circuit, so when the cabin-lighting breaker is on, we also have USB power. Seems to be a reasonable choice so far.
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Old 07-05-2016, 11:57   #13
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Re: USB jacks phantom loads

I added switches to mine, the idle current was >15mA. and I have several around the boat.
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Old 07-05-2016, 12:32   #14
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Re: USB jacks phantom loads

I install 12volt barrel plug outlets in the vee, galley, and on deck. Then I put an inexpensive auto USB device into the 12v outlet.

This is a more generic, simple, and effective solution. For example, when they came out with high amp USB for ipads, I didn't have to rewire, like you would if you hard wire your USB. Also, the 12volt jack is useful for lots of other stuff, like a portable DVD player, spotlight, small inverter, and my most favorite...a digital voltmeter (that goes right into the 12volt plug).
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Old 07-05-2016, 13:00   #15
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Re: USB jacks phantom loads

What you are missing is that all USB outlets are not the same, by a long shot. You are FAR better off with a standard cigarette lighter socket, then customize with a USB plug-in.

The basic USB socket provides max 500mA (0.5A) at 5VDC. High power charging USB ports can provide more than 2.0A @ 5VDC. However, there are several standards for communicating between charger and device, and you will need sockets that understand your device. It is becoming common for sockets to be "intelligent" and that can recognize several protocols, but I have not seen these in permanent wall mounts. Apple's iPhones use their own set of protocols (and cables), which often are not fully covered even with intelligent sockets. There is also a movement starting to switch from USB A sockets to USB C sockets, and some phones will want to use USB C cables to get the maximum charge rate. And just to confuse things more a new USB standard allows for higher voltages, and Qualcomm has implemented this in their QuickCharge (,2.0,3.0) system - my phone charges using 9VDC with this.

Given this complexity, you will want to buy a USB adapter that will match the needs of your devices - and this is a moving target. Building into the boat a very basic USB port will be of limited use, as you will want specialized ports for your phones and tablets.

Greg
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