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Old 17-06-2013, 10:18   #1
Guy
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12v Power Supplies

No doubt asked before but is there any reason you cannot regulate the boats DC power down to an even 12v and do without all the little transformers for 12v electronic goodies? Also, could there differences between different kinds of 12v regulators?
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Old 17-06-2013, 10:34   #2
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Re: 12v power supplies

Not sure what the question is.... you mean 120v/12v wall warts? Many "12v" applicances are rated something like 11-18 volts...
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Old 17-06-2013, 10:44   #3
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Re: 12v power supplies

I believe you're asking if small electronics devices which require 12VDC can be run off the ship's 12VDC power.

The short answer is yes. Most "12V" appliances and devices these days can take a fairly wide range of voltage and can easily accommodate the fluctuations in the boat's 12VDC power. These usually range from about 12.0VDC for a very deeply discharged battery to about 14.8VDC for batteries under charge.

However, the real answer is "it depends on what you're trying to do". Some of those 12VDC devices draw quite a lot of power. For example, older laptops may draw 7-8 amps @ 12VDC. In totality, you might be putting a healthy load on your house batteries with a multitude of "12VDC devices".

This would be no problem at all if you were dockside and plugged into shore power with your battery charger on. Or, if you were away from the dock and had a good source of charging, like big solar panels or a wind generator.

So, yes, you could do it. But you need to think about which devices you really want to run off ship's power, and which ones might better be run off shore power or an inverter.

Bill
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Old 17-06-2013, 11:04   #4
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Re: 12v power supplies

So if the boats dc power ranges from 12.9 to 14.5vdc it will work fine for a electronic gadget that calls for 12.0 vdc ? We have plenty of power on the boat.
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Old 17-06-2013, 11:17   #5
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Re: 12v power supplies

Yes, most likely. What's the gadget?

Do you have the instructions? Look also at the plate affixed to the gadget...that sometimes has voltage levels printed on it.

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Old 17-06-2013, 11:27   #6
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If you look around online you can find 12vdc power supplies for any laptop. You can also get 12v USB chargers for phones and iPads etc. and most all cordless power tools offer 12v chargers. I even have a 12v shop vac, it does not suck nearly as well as a 120 volt vac but it works.

If you actually put a meter on an average running cars 12 v outlet it will read 14.4. My iPhone does not seem to charge well at voltages under 12.1vdc.
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Old 17-06-2013, 11:27   #7
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Re: 12v power supplies

Quote:
Originally Posted by btrayfors View Post
Yes, most likely. What's the gadget?

Do you have the instructions? Look also at the plate affixed to the gadget...that sometimes has voltage levels printed on it.

Bill
There must be a half dozen of the bricks plugged into a power strip from the inverter. Many of them say 12vdc, some are another voltage so they would still need their own power supplies.
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Old 17-06-2013, 11:36   #8
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Re: 12v power supplies

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There must be a half dozen of the bricks plugged into a power strip from the inverter. Many of them say 12vdc, some are another voltage so they would still need their own power supplies.
EBay do a load of regulated power supplies, do a search for "regulated DC/DC boost power."
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Old 17-06-2013, 12:04   #9
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Re: 12v Power Supplies

Hi! Look at each power supply's "brick label"! The listed voltage might be around 12 VDC, but the current requirement/consumption for each "brick" may be different; hint...this is your limitation on how many bricks can be connected to a single power source.

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Old 17-06-2013, 13:40   #10
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Re: 12v Power Supplies

There are (unreg.12/reg.12) regulators around and you can use one where you need regulated 12V.

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Old 17-06-2013, 14:09   #11
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Re: 12v Power Supplies

Guy, you will find that some of the 12v bricks out out as much as 17v under no load. The newer ones, that use switching regulators instead of transformers, tend to be more tightly regulated and will remain at "12.0".

As to what the gizmos will tolerate, there's no way to be sure if they will tolerate over 14 volts without contacting the manufacturer, who these days will probably tell you "we can't comment on that due to liability reasons".

On the other hand, you can go to Radio Shack or any electronics house and for abot a buck apiece, buy a cheap 12 volt 3-terminal regulator rated for up to 1.5 amps, and just install one of those in each powerline. With some caveats, since most of them will require at least a 13v supply to put out 12v. A "low loss" regulator will cost a bit more, as will higher power ones.

Your solutions will depend on how techie you want to get, and how reliable you want the solutions to be. A lot depends on how expensive the gizmos are, if you wind up blowing them out.
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Old 17-06-2013, 15:59   #12
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Re: 12v Power Supplies

Unfortunately, you can not use the Radio Shack 12 volt regulator chips to regulate a 12 volt battery system to 12 volts output. Most of these require the INPUT voltage to be about 1.5 volts greater than the output voltage, thus the input needs to be greater than 13.5 volts for the regulator to work properly. If you are slightly handy, you can buy fixed-voltage 12V chips in the Micrel 29000 series. These are low-dropout regulators which only require the input to be about 12.2 volts to get regulated 12 volts out. And if the voltage is less than 12.2, they will simply stop regulating and let the output voltage drop. All they require is 2 small capacitors and a heat sink.

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Old 17-06-2013, 16:15   #13
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Re: 12v Power Supplies

"Unfortunately, you can not use the Radio Shack 12 volt regulator chips to regulate a 12 volt battery system to 12 volts output."

That's what I just said, Rick. 13 or 13.5, doesn't matter, it is more than battery voltage and less than alternator voltage. As Chairman Mao said "Black cat, white cat, all same, catch mice."
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Old 17-06-2013, 18:56   #14
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We have two laptops, an iPad, a Droid Bionic phone, a Kindle, and two Sansumg 7 tablets. We have been muddling through this question since we moved aboard on May 11th.

We have found all the iOS and Android devices charge and operate no matter what the voltage of our battery (plugged in via a 12v USB Adapter). I've read they only need 6v to 12v.

The laptops will charge very slowly if they are turned off and the battery is producing less than 13v. They will slowly discharge if turned on, plugged in with less than 13v.

The laptops will charge properly if the voltage is 14v+. This occurs during the day when our 80W solar is producing power.

Our solution is to only charge the electronic devices during the day. This seems to work so far. The solar usually produces enough power to recharge our devices and run our ST4000 during the day plus enough to charge the battery to run our incandescent anchor light, LED cabin lights, and LPG controller at night. We do not have refrigeration or a watermaker (yet....).
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Old 17-06-2013, 20:20   #15
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Re: 12v Power Supplies

A search on ebay for "DC-DC converters" will turn up many possibilities, all more efficient than a simple linear regulator. I would go that route if a regulated voltage was needed, either above or below 12v.
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