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Old 25-09-2015, 19:16   #1
RDW
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USB outlets

With all the devices on a boat with friends and their I phones and I pads, I am thinking of putting in some USB outlets for charging.
Does using a USB outlet running off 12 Volt DC save much energy compared to running an inverter, using 120 AC with a converter to get DC charging?
There are USB outlets that would be wired to 12 volt DC and there are 120 volt AC outlets with built in USB outlets in addition to standard 120 volt AC outlets.
I have to think using the DC wired to a USB has to be more efficient. Anyone got any idea how much more?
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Old 25-09-2015, 19:26   #2
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Re: USB outlets

ask BlueSeas... they would know.
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Old 25-09-2015, 19:57   #3
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Re: USB outlets

Dc wired is more efficient by quite a bit. Blue seas has a dual usb socket. Put one on my boat snd its great
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Old 25-09-2015, 20:03   #4
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Re: USB outlets

Well, it mostly depends on the inverter. I have some dual-USB sockets, as well as some USB adaptors that plug into my 12V cigarette-style sockets. These draw practically no current when nothing is plugged into them, and seem to be reasonably efficient at turning 12V into the 5V USB voltage. Sorry, I don't have hard numbers handy, but I'm glad I installed them.
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Old 25-09-2015, 20:29   #5
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Re: USB outlets

I haven't found any of the dedicated USB outlets that support 2.4 amps. I opted for 12v sockets and separate USB chargers supporting 2.4 amp.
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Old 25-09-2015, 20:39   #6
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Re: USB outlets

I've had a lot of success from Burns Moto They also take 12v or 24v input. I've ran them on motorcycles through torrential rains and they have worked flawlessly. I haven't seen any that support 2.5a. Curious what you need that for?

Doug
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Old 25-09-2015, 21:07   #7
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Re: USB outlets

re; amp ratings...

I'm running cabin lites; 3 banks of 4 heads with three cree (?) LEDS each,( tat's 36 total)!!) from one 12vdc/5vdc cig adapter courtesy of the local stop-n-rob store. . It has/had two ports; one @ 1.2 a and one @ 2.2a.
All lit up for the last few hours and the plug/wire lash-up is barely discernably warm

I'm also considering USB ports in the quad recept boxes I'm gonna put in. Just not sure if I'm wanting cig adapter sockets all over; or std. 12vdc barrel connectors???
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Old 25-09-2015, 21:20   #8
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Re: USB outlets

There is only one USB AC outlet combo I have found that supports dual charging for tablets: http://www.amazon.com/gp/product/B00...ilpage_o08_s01

This provides 4A - either 4A in one or 2A for both or any combination thereof.

For DC, there are plenty of options that provide higher charging for tablets, etc.

We have the above AC/USB outlets installed (just makes sense to get these if one is replacing an outlet anyway), as well as some DC ones scattered about.

As mentioned, the efficiency is determined by the overhead of the inverter. None of the items being charged draw much power - maximum of 2.2 amps for a tablet. So if your inverter has a 2A overhead just to be turned on, then this isn't efficient. If the inverter overhead is only some milliamps, then the inefficiency of inverting is negligible.

More and more, USB outlets are supplanting all other types of power outlets on our boat.

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Old 25-09-2015, 21:25   #9
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Re: USB outlets

dc is better. It's simpler to wire in it's just going to convert the 12v down to 5v anyways. With AC your converting it to ac then back to dc with the plug so you have more conversion which is bad since you lose power basicly.

DC is simpler to wire in simpler to hook up can be wired directly to the battery if you wanted to just positive negative.

If you want to wire it direct put something in between so it doesn't drain your battery fully as it can drain it down to nothing if you directly hook up. You will find most electronics are dc power with a bar to convert it from ac to dc.
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Old 26-09-2015, 06:15   #10
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Re: USB outlets

USB outlets are indispensable nowadays.

Two things I'd like to add to the discussion:

1) Consider that there's an overhead to running the inverter. My inverter goes into a "sleep" mode when nothing is drawing power. Do you really want to run the inverter all the time you're charging your devices? Even if you run the inverter 24x7 for other appliances, your phone is a safety item. Do you want it to depend on AC power?

2) Buy an assortment of high-speed charging cords. Your guests will inevitably forget theirs.

But be careful. A cord may claim to be "capable" of high speed but not deliver unless it's plugged into the right brand of AC charger.

However, you can buy a smart USB adapter that senses the device plugged in (iOS or Android) and adjusts the voltages on the data pins accordingly, so it's always seen as a fast charging port. Or, from the same manufacturer, you can buy cords (standard micro-USB or Lightning) that are internally wired to provide the right signal, making any port a high-speed port. With modern devices, charging at high speed can mean the difference between a 30-minute charge and a 10-hour charge!
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Old 26-09-2015, 06:49   #11
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Re: USB outlets

I am reluctant to hard-wire anything which is likely to go obsolete quickly, so have not put in any hard-wired USB sockets. I think it's better to put in DC cigarette lighter sockets and use USB car chargers.

I don't really bother with either since my inverter runs 24/7 anyway and there may be a dozen or more devices charging at any given time, depending on how many people are on board.

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Old 26-09-2015, 06:55   #12
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Re: USB outlets

Given the popularity of USB charging, I installed a smart multiport charger, 12V input, last year. Provides sufficient amps to charge tablets etc.

Away from the boat and dont recall the brand, but similar to these:

http://www.amazon.com/s/ref=nb_sb_ss...2Cmobile%2C465
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Old 26-09-2015, 06:59   #13
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Re: USB outlets

Quote:
Originally Posted by Dockhead View Post
I am reluctant to hard-wire anything which is likely to go obsolete quickly, so have not put in any hard-wired USB sockets. I think it's better to put in DC cigarette lighter sockets and use USB car chargers.

I don't really bother with either since my inverter runs 24/7 anyway and there may be a dozen or more devices charging at any given time, depending on how many people are on board.

Sent from my D6633 using Cruisers Sailing Forum mobile app
The "USB" hard wired items fit into a typical cig plug size hole. Cig plugs are stupid and hardly suited for marine use but very common. I WAS using USB doubles that plug into a cig plug.. but I am going to change them because I don't use many cig divices...

This is ALWAYS a problem when you fit something to the boat...
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Old 26-09-2015, 07:50   #14
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Re: USB outlets

iPad Charging - 12V vs. Inverter - SailNet Community


This is a post which showed in one particular set up the dc to dc was 29% more efficient. It was a small amount like about 5 AH to fully charge an I pad but it all adds up.
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Old 26-09-2015, 09:16   #15
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Re: USB outlets

In that test, he was using a cheap Walmart MSW inverter, which accounts for 25% of that 29% inefficiency. Transformer loads like a wall charger just HATE MSW inverters. Some to the point of burning up.

I could chose an inverter/charger setup that is even more inefficient if you want to see even greater differences. Or I could show you a similar setup with <5% loss of efficiency that wouldn't be noticeable in practice.

The AC/USB combo outlets I posted would have essentially no efficiency losses - particularly when you consider that charging is going on when you are using the AC outlet for something else anyway.

Mark
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