DC To AC Adapter

[WeaponX 0]

Hi, I'm looking on getting an DC to AC adapter for my car. I want to use my laptop on the car and since the battery won't hold my charge anymore, I need one of these adapters. How many watts/volts should I be getting for using it on laptops? Also, can I use it for lower voltage devices like a cell phone charger?I'm looking online for these adapters and have seen ones that have one side for the cigarette lighter and the other end is like a regular power outlet socket. Are there any that have a direct cable from the laptop's power connector to the cigarette lighter? Just wondering about this one...Anyone know how much power it will take from the car's battery? Just don't want it to guzzle the battery dry Thanks.

[vizskywalker 0]

First fo all, that's not a DC to AC adapter. Laptops (like all computers) take DC power. Most Desktops have a built in power supply to convert AC power to DC, which is why you plug them directly into the wall. Laptops have the box on the power cord to perform the conversion. Second of all, check with the maker of your laptop for a car adapter, as many make them. Otherwise, check the box on the main cord and it will say "OUTPUT: 19V 4.74A" (or similar numbers) this is the voltage and amperage that your computer runs on. You should be able to find an adapter in a store like CompUSA using those numbers. And a sales associate will also be able to help. But check with your laptop's manufacturer first.~Viz

[kam1405241509 0]

Hi WeaponX :-),

like vizskywalker said, you don't want a DC to AC adaptor if you can avoid it. Ideally you should try to find something that plugs into the cigarette light (12V on current cars ... soon future cars will move to the 40V standard but I'm not sure when that will happen .. there was something in an IEEE Spectrum mag a few years ago about that).

Anyway, if you can't find the above, then get what I bought from the UK shop Maplin (I'm sure any electronics store in the US will have the same parts .. maybe there's an RS or something in the US?) .. what you'd need is a 800W soft start power invertor at 12V. It will look like a box that has a standard "wall" outlet in it that you plug your laptop/PC's power plug into, and then a cigarette lighter socket at the other end. Mine converts 12Vdc to 230Vac .. and it runs my car-PC just fine . But as with all convertions, there is some efficiency loss (mine if officially at 600W, but my PC cuts off if I actually go to 570W load).

Finally, your question about power consumption. You can test your loads with a watt-meter before actually trying it out in the car etc. Also, you're in a car, so if you don't mind a little extra fuel consumption, you could always just carry an extra batt in the boot. Finally, I've never had a problem of running out of juice. My car (and I think most cars) trickle charges up the battery when you drive and are not using it (I only use it for GPS, and some mobile emailing/documents/etc nothing serious .. it doesn't really go over 100W .. but that's because it is a low power PC). AFAIK, there's no serious limit to recharging lead-acid batts, and they should last for ages :-).

You might be interested in other car PC projects (google for car pc), and for other low-power small PCs (google for mini-ITX and nano-ITX).
http://www.mini-itx.com/ is one of my fave sites.
Also, there was a recent IDF demo (the one that was just held!) where an intel researcher (Bill Sui) connected his PC to a car-battery, and he'd written some UPS-like code for it etc. He had another cool demo: "Sweet, huh? If that's not cool enough, the front of the machine also sports a hard button that enables the PC to roll back to a safe point upon a problem with the machine - effectively wiping the hard drive and rolling back to a stored disk image. It's kind of like System Restore Points in hardware, on steroids." (http://www.bit-tech.net/news/hardware/2005/08/23/intel_pc_car_battery/1; http://forums.bit-tech.net/showthread.php?p=1049296).

In that latter URL are 3 relevant posts .. "Believe it or not, but a car battery will actually power a typical computer for longer then a lot of the more expensive UPS's actually do. Friend of mine runs an inverter in his van, and with his system (2.8 p4, 2 hdd, 2 optical, 6600gt, 350watt psu) and his monitor (15"), and the battery will last (with the van off and the dome light on) roughly half an hour or more."

and
"Powering a PC with a UPS is very inefficient, basically because the UPS circuitry goes from DC to AC (inefficiencies in the inverter) then the PC goes from AC back to DC (with more inefficiencies in the PSU). What Intel have done is strip out the conversion stages, and provide 12V straight to the power circuits (which is the same thing that happens with SFF PCs that use an external power brick)."
The external power supply the above mentioned is at the mini-ITX.com's site's shop ... very very cool (this is what I ideally want to get eventually!!)

and finally "What's so inovative about this? There are plenty of DC/DC power supplies for PC's out there.. One such supply is a 90watt dc/dc 6-24v input for 69usd. There are actually many companies that make atx spec dc/dc psu's out there."
There's a link to an American shop selling the above which might be useful for ya . You didn't tell me what power consumption your laptop is, but my guess is that the 800W invertor route is the least elegant (but is very flexible if you want to run other appliances off of it!!).

hope this helps & was fairly clear,
if not feel free to ask more details .. car-PC's are definitely a lot of fun to setup (er, and use ) .. and eventually I'm sure everyone will have one ,
Kam.

[WeaponX 0]

Thanks for the replies. OK, I will look online for one of these adapters to plug into the cigarette lighter. The laptop adapter says:Output: 12V 6.0A 120W

[kam1405241509 0]

Thanks for the replies.  OK, I will look online for one of these adapters to plug into the cigarette lighter.  The laptop adapter says:

 

Output: 12V    6.0A  120W

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Depressingly I couldn't find Maplin's 800W version online .. I'm sure there is/was one! Still Maplin UK has a 600W one for 40GBP (http://www.maplin.co.uk/?doy=8m10&ModuleNo=36316&). It's quite small (you could tuck it in the boot, glove compartment or even under a seat with a mini/nano-ITX board/case).

 

I got this link off of a Google search for 12Vdc to 230Vac (https://www.portablepowertech.com/?aspxerrorpath=/productslist.aspx) and they go up to 2000W!! This reminded me that car/caravan & yacht/boat & airplane electronics shops have these too .. along with lots of other cool electronics like navigation, motorised satellite TV antennas, etc ... even for fast moving vehicles! 802.11/15/16/etc standards are also related interesting future tech to look at if you'd like wi-max like data rates for Net access from a fast moving car ;-). I can't wait for this, it'll totally change the current telco dominated landscape of relatively slooow & expensive 3G access ;-). Er, sorry for the tangent, I do that a lot.