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Old 13-08-2018, 13:36   #31
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Re: Useful 12vdc Devices

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Originally Posted by Jim Cate View Post
How are they for RFI? Lots of dc-dc converters are noisy as hell.

Jim
The first 12v~18v convertor I bought ( not cheap) was a dedicated one for a Macbook...... noisy as....

Then I discovered these DCDC-USB-200, Intelligent DC-DC converter with USB interface

I salvaged the cable and plug from the original crappo unit.....

A light and gentle hum on some frequencies but not bad enough to turn equipment off... just as well as it powers ship's PC, LG screen, as well as charging the Mac all of which want 17/18V

OK... I unplug the charger from the Mac when getting NOAA sats as it does affect the picture quality slightly.

I also , back in the dreamtime when my PCs and screens wanted 12v rather than 18V , used their 12/12 units to do away with any voltage drop issues when engine starting, etc.
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Old 13-08-2018, 13:50   #32
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Re: Useful 12vdc Devices

the Ryobi ONE+ battery platform powers hundreds of tools and gadgets, transitioned from lead to NMH to LiPo now, has been consistent for many years and they promise to not change it.

Their from-12V chargers are not expensive, and the batteries from 4AH up have a great warranty from Home Depot, bigger ones coming soon.

There are hacking howtos on the web to use as portable powerpaks for charging phones, USB etc, 18-19V laptops should just be a matter of getting tip size and polarity right.
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Old 15-08-2018, 21:04   #33
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Re: Useful 12vdc Devices

Great thread btw. I have a surface laptop, they make a 12v plug to laptop cord standard. Doesn't need the higher v other laptops need.
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Old 16-08-2018, 04:21   #34
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Re: Useful 12vdc Devices

Be careful though connecting "12 Volt" laptops directly. Your boat voltage my be anything from 11 Volt to maybe 16 Volt or beyond. You may fry something now and then.

I know this from using "12 Volt" routers plugged in directly into the battery. But such routers are 5 to 10 dollars worth, not hundreds of dollars.

Now some laptops are driven from 5 Volt USB plugs. And a 5 V plug does not call for any expensive inverters, only a step down device universal to any phone, tablet or camera or lithium battery bank.

My future boat laptops will be 5 Volt USB devices.

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Old 16-08-2018, 04:32   #35
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Re: Useful 12vdc Devices

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Originally Posted by smith8273 View Post
The link to the 12 WiFi router is broken, I’m interested in a 12v one, please repost.


I didn’t post about the 12v WiFi router, but here’s the one I’ve been using:

TOTOLINK AC1200 Dual Band Wireless WiFi Router, wifi speed Up to 1200Mbps (A3) https://www.amazon.com/dp/B071CN3C12..._fawDBbK668GM4
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Old 16-08-2018, 05:45   #36
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Re: Useful 12vdc Devices

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Originally Posted by barnakiel View Post
Is it easy to step UP too?

I always imagined stepping down is just a resistor.

How do you step up DC?

There is no transformer, you know, these work on AC only.

???
b.

DC droppers use buck converters, not resistors, for reasons of efficiency. Buck converters are a kind of switching power supply, which are extremely efficient.



DC conversion to increase voltage is done with a "boost converter" -- see: Boost Converter Design


Both are cheap and efficient. You can buy small buck converters, boost converters, or combined buck-boost converters, for a couple of dollars, to power any kind of small electronics. I have probably a dozen on board my boat. Most of them made by DROK, but some expensive ones which were part of my boat's original build (she's 24v so has droppers for some 12v equipment).



HOWEVER, as someone noted, these devices, like switching power supplies of other types, often cause a lot of RFI, which can be a real problem if you operate HF radio, and could cause other kinds of interference.
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Old 16-08-2018, 06:41   #37
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Re: Useful 12vdc Devices

Laptops and other devices designed to run off 12V will actually do just fine in a large range, say between 11 and 16V.

Especially expensive ones charging internal batteries.

For cheap ones without, or expensive gear you want to coddle, feed a 12V circuit with a "stabiliser" basically 12V-12V converter, that accepts that wide range of input, but puts out a steady say 13.8V.

You can do the same for 5V USB, and 19V where that is required.

All these options are much more efficient than running through an inverter to go 12V to 120AC, then the device power brick from AC back to the native DC.
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