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Old 12-12-2010, 11:35 PM   #1
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My TV and my laptop use 12 volts anyway, so ...

I'm working on everything right now, getting ready for a trip to Florida after Christmas .

We got a Vizio LED LCD HDTV as a second TV we can use with an antenna, to sit by the fire and watch a ballgame and other broadcast programs. TV is low on the priority list, but it would be nice to have on our trip for news and weather, any football games we might want to watch, nothing as complicated as cable or satellite.

At home, we have been experimenting with the TV, and find we can locate the available channels with a Winegard antenna, FreeTV, small model, that does a great job of picking up HD channels. I've figured out a good way to get it set up on a portable basis (nothing installed on the roof yet) for the infrequent times we will use it.

The TV uses 12 volts converted from 110v by the box on the end of the cord that plugs into the 110v receptacle.

Same with my MacBook laptop -- it has a converter built into the cord to bring 110v down to 12v.

Can we create a 12v system from either the battery or the Univolt, to power these two low-energy devices, without going through the usual 110v to 12v conversion, when both only use 12v, after all? I guess we also want to work our way into becoming more skilled at camping "off the grid", more than the transient overnights in church parking lots on our trip to Florida.

What would we need? 12v regulator? Battery monitor? I am starting to realize the cool old "Control Center" in the Trade Wind is going to be replaced eventually by modern gauges. The amp meter on the Control Center may not be working properly.

I read on another forum that someone cut the converter off the factory power cable for the Vizio LED LCD HD, and wired on to the cord an automobile 12v round adapter, plugged it into a 12v auto receptacle, and was enjoying the TV.

When it comes to the TV, being brand new, I don't want to cut the factory cable in case I need to return the TV to the store (we are not happy with the sound quality, and may want to try another brand).

Even though the laptop is out of warranty, it's a nice laptop, and I still don't want to do anything to harm it.

Having a consistently 12v power source is important, for both "appliances", no? And, having the power supply fused for a possible spike (from the park electrical service, for example) would be important, right?

Is this possible? What might be some safe ways to configure these power cords safely, and not risk destroying the TV or the computer? What would the expense be like, ballpark estimate?

Thanks,
Anne
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Old 12-12-2010, 11:57 PM   #2
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hi anne

does your stream have 1 or 2 or 3 round 12v outlet/plugs?

if so, just purchase an inexpensive 150-200 watt inverter and use one of the 12 volt plugs.

these work fine and are more than adequate for small/mid sized lcd teles and puters.

there is a tiny bit of 'wasted juice' but it's not much and worth the simplicity.

i have used these for many years while off the grid and without a single negative outcome.

many threads on lcd, puter and small inverter usage here,

here is but one...

http://www.airforums.com/forums/f314...tml#post766780

cheers
2air'
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Old 12-13-2010, 04:21 AM   #3
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For laptops it's best to use something like this:

Amazon.com: Car Charger Dc Laptop Adapter Power Cord for Apple Mac: Electronics

I use something similar for my Lenovo.

They plug into the round cigarette lighter type outlets that 2air described. If you don't have those on your trailer you can add them easily enough.

I can't help you for the TV although as you note people have run successful experiments just running 12 volts straight in.
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Old 12-13-2010, 09:12 AM   #4
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Thank you, 2air and Jammer. The direct 12v option seems most efficient, but the power regulation is also important.

I do have an inverter, and 2 round cigarette type 12v receptacles in the Trade Wind. I can also take this opportunity to test out the 1968 splitter/amplifier for the antenna, located in the same wall fixture in the front, used to be the dinette area, now front bedroom.

Lots going on, making some progress, but my camera is broken. When the iPhone has enough light, I'll post some pics. Should have some snow reflection to help illuminate some of the work areas.

Thanks again,
Anne
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Old 12-13-2010, 09:21 AM   #5
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Watts & Amps and Car Charging

Jammer, the link you sent for the adapter on Amazon looks great for the MacBook. I noticed in the specs it is 85 Watts. I am learning, but not yet enough, about electricity. Would 85 Watts be 8.5 volts or 8.5 amps? One user said, "It draws much less power from the car battery than using an inverter and my AC power cord," which is what I'm looking for.

Another question: is it possible to put an in-line fuse on this adapter, to manage any spike that might happen, or unexpected power draw from the laptop that could damage the Airstream wiring?

I added a bigger hard drive 350 Gb, 7200 rpm, that runs faster than the factory drive 80 Gb and 5400 rpm. I fear that might draw too much power??? (voice goes up in a question )

Thanks,
Anne
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Old 12-13-2010, 09:25 AM   #6
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12v to 12v converter

Found this on another forum:

SD-50A-12, Mean Well SD-50A-12

But -- uh oh -- "TRC Electronics is a Business to Business sales company. We sell to OEMs and CMs. Our wholesale prices do not permit us to sell to consumers or end-users. We lend our power supply expertise to Electronic Manufacturers only."

Anne
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Old 12-13-2010, 09:31 AM   #7
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Quote:
Originally Posted by IndyAnne View Post
Jammer, the link you sent for the adapter on Amazon looks great for the MacBook. I noticed in the specs it is 85 Watts. I am learning, but not yet enough, about electricity. Would 85 Watts be 8.5 volts or 8.5 amps? One user said, "It draws much less power from the car battery than using an inverter and my AC power cord," which is what I'm looking for.

Another question: is it possible to put an in-line fuse on this adapter, to manage any spike that might happen, or unexpected power draw from the laptop that could damage the Airstream wiring?

I added a bigger hard drive 350 Gb, 7200 rpm, that runs faster than the factory drive 80 Gb and 5400 rpm. I fear that might draw too much power??? (voice goes up in a question )

Thanks,
Anne
Anne,

I am not sure how tight the voltage tolerances are on your Macbook or your TV however it seems like a 12 volt regulator is what you need. As for the increase in storage and more rpm this current draw is negligible.

Also you might be able to find a pre made converter for the computer off e-bay that would fit your need. This would prevent you from damaging your current power supply. If not visit the apple store and see if they have any that customers returned as defective.

Chris

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Old 12-13-2010, 09:59 AM   #8
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not 2 make this into a mac thread, but this is what i use JUST for the mac...

HyperMac Pure DC Car Charger for MacBook

didn't mention it in the first post, since they are now HARDer 2 find.

it was d/cd last month after apple filed an infringement licensing/issues lawsuit against the company.

as a 'pure 12v' solution it has worked great and is trouble free.

totally bypasses the mac brick and came with the apple mag safe adapters for mbpro AND mb.

i also use the same companies lithium battery pack in a size that triples the internal battery capacity.
__________

there are a FEW (currently 9...) of these still available from some of the mac vendors like ifixit.

http://www.ifixit.com/Apple-Parts/Hy...it/IF179-019-1

and used/refurbs may show up on 'bay or c-list.

cheers
2air'
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Old 12-13-2010, 10:27 AM   #9
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Hey, 2air, the more Mac the better, I always say!

Looks like that charger is going to be hard to find. If you run across another source, would you mind sending me a message?

I'll check eBay and web.

Anne
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Old 12-13-2010, 10:28 AM   #10
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Chris,

Thank you for the tip!

Anne

Quote:
Originally Posted by 2airishuman View Post
not 2 make this into a mac thread, but this is what i use JUST for the mac...

HyperMac Pure DC Car Charger for MacBook

didn't mention it in the first post, since they are now HARDer 2 find.

it was d/cd last month after apple filed an infringement licensing/issues lawsuit against the company.

as a 'pure 12v' solution it has worked great and is trouble free.

totally bypasses the mac brick and came with the apple mag safe adapters for mbpro AND mb.

i also use the same companies lithium battery pack in a size that triples the internal battery capacity.
__________

there are a FEW (currently 9...) of these still available from some of the mac vendors like ifixit.

HyperMac External Battery and DC Charge Kit - iFixit

and used/refurbs may show up on 'bay or c-list.

cheers
2air'
Quote:
Originally Posted by ck21084 View Post
Anne,

I am not sure how tight the voltage tolerances are on your Macbook or your TV however it seems like a 12 volt regulator is what you need. As for the increase in storage and more rpm this current draw is negligible.

Also you might be able to find a pre made converter for the computer off e-bay that would fit your need. This would prevent you from damaging your current power supply. If not visit the apple store and see if they have any that customers returned as defective.

Chris

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Old 12-13-2010, 10:32 AM   #11
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Macbooks do not take 12 volts - they take 18.5 volts. You need a DC-DC converter if you do not use some form of AC.
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Old 12-13-2010, 10:33 AM   #12
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HyperMac options

2air,

That Hypermac bundle looks great! The cost is a bit steep for my current cash flow.

I also found this in the search: "Apple Sues HyperMac Accessory Maker ..."
http://www.appleinsider.com/articles...od_cables.html

This reminds me, however, that I bought a little InspireOne last year, for foreign travel, maybe that can be my email machine in the AS, and leave the MacBook home.

But, I was hoping to let the MacBook double as the DVD player, internet radio, Skype video phone, and other good stuff, along with the LED TV.

Hmm.

I'll keep working on it.

Anne
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Old 12-13-2010, 10:38 AM   #13
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Dave,

Thanks for prompting me to check the brick. I have the MacBook1,1 -- maybe the first version of the black 13" MacBook. The brick reads 16.5v, 3.65 amps. That would take a different DC/DC.

But, the TV is definitely 12v 4.58 amp output from the brick.

This is getting intere$ting,

Anne

Quote:
Originally Posted by Dave Park View Post
Macbooks do not take 12 volts - they take 18.5 volts. You need a DC-DC converter if you do not use some form of AC.
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Old 12-13-2010, 01:00 PM   #14
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Quote:
Originally Posted by IndyAnne View Post
Jammer, the link you sent for the adapter on Amazon looks great for the MacBook. I noticed in the specs it is 85 Watts. I am learning, but not yet enough, about electricity. Would 85 Watts be 8.5 volts or 8.5 amps?
Laptop power supplies are complicated. I don't know about the MacBook in particular but most laptops/notebooks have a power supply with some sort of signaling and control. Some may be as simple as a voltage sense, or as complex as a connection to a microcontroller in the power supply that can identify itself and turn the power up, down, and off.

For this reason it is generally unwise to try to engineer your own DC-DC power supply for a laptop unless you are really good at that sort of thing, good enough that you cam maybe patch the laptop electronics if you burn them up.

But, to answer your question, in this particular case 85 watts is 18.5 volts at roughly 4.5 amps.

Quote:
One user said, "It draws much less power from the car battery than using an inverter and my AC power cord," which is what I'm looking for.
Depending on the inverter the savings in power may not be that great (10-20%). The real benefit is less cord mess.

Quote:
Another question: is it possible to put an in-line fuse on this adapter, to manage any spike that might happen, or unexpected power draw from the laptop that could damage the Airstream wiring?
There should be a fuse or circuit breaker between the battery and the 12v outlet in the Airstream. That's all you need.

Quote:
I added a bigger hard drive 350 Gb, 7200 rpm, that runs faster than the factory drive 80 Gb and 5400 rpm. I fear that might draw too much power??? (voice goes up in a question )
Have no fear, for two reasons.

Reason first. Part of the reason laptop power supplies are so complicated is that they adjust for this sort of thing.

In general terms, the laptop will reduce the amount of power used for battery charging to the extent necessary to stay under the maximum output of the power supply.

Reason second. Hard drives don't use much electricity. In a laptop, the display and the CPU have the largest power draws.
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