Thread: Powering tablet PC straight from cig lighter power?

Originally Posted by Brib3

Hi. I have a quick question. In the process of building my carputer (i'm using a HP tc1000 tablet PC motherboard) I hooked up a 12V power adaptor instead of the required 19V power one. It ran just fine until I figured what I have done . I know that the reason why people use power supplies and such is because at crank, the power from the cig adapter exceeds 12V.

Since my carputer worked fine with 12 V, and it requires 19V, is it safe to assume that I could power it from the cig adaptor?

Thanks.

PS. I do have a carnetix P1900 power supply, but I need 12V for the monitor and 5V for powering USB and I do not have the 3rd 5V module.

You are somewhat mistaken.

The cars power source, the battery and alternator, fluctuates, both above and below 12 volts, that is why using the 12volts from the car to power a 12 volt device, is a bad idea, no matter where you take it from.

The major issue with the Cig Lighter is the lack of AMPERAGE/WATTAGE available. Most cig lighter sockets are speced to about 5 or 7 amps, or 60 to 75 watts. Drawing more from there is a bad idea, since the wires that go from the battery to the cig lighter, are thin and will most likely burn, and cause your car to be a hulking piece of red molten metal.

Supplyinh less then the needed power to your devices, while not "lethal" to the equipment, it will most likely cause it to act erratically. You will have wierd issues that will be perplexing, like reboots, and read and write errors, and just strange operations.

DO it right, don't skimp, it will save you time and headaches.

Michael

You know when I first skimmed this article in my RSS reader, I went right by it cause I figured you had an OEM auto adapter and plugged it into the cig lighter. On the second perusal I realized this was not the case.

Let me start by saying, "Did you know computers run on smoke? Yea, when the smoke escapes, the computer quits running."

The above is what you have to look forward to if you continue as you are. I learned this lesson firsthand over twenty years ago and have never forgotten it, nor let my customers forget it. In a home/apartment/condo, etc if the lights dim when the heat or A/C comes on, this is called a brown-out condition (the main draw, A/C, takes so much power that other appliances recieve not enough power). Brown-outs kill computers over time. My little Commodore 64 back then smoked cause it wasn't protected by an appropriate over and under voltage surge protector (not all surge protectors are equal).

O.K. back to your situation - laptops and tablets are resilient but not this resilient. Sure it may run on 12-14 volts versus 19 volts, but this stresses the millions of diodes and transistors expecting a clean, constant voltage. It actually may run this way for up to a year, but sooner or later one or more of them will burn out - best case computer starts acting erratic and eventally power supply burns out/worst case you get a cascading failure (imagine dominoes one sparks causing the next to spark and so on), see the smoke, and it stops working all together.

Bottom line get the car adapter cut the cig lighter off the end and power it from an appropriate amperage fused line. I split mine off the ACC coming into the fuse box, added an inline fuse. When ACC shuts off, my tablet initiates its "on battery" power scheme, i.e., screen blanks after 1 min, at 20 mins it goes to standby, then at one hour it fires back up and hibernates. I've considered a startup controller but the "ON" button of my tablet is more accessible than the one on my head unit so its not too much trouble to turn it on when I get in.

Good luck whatever you decide, you have been warned.

OK. I get the point . I kind of had the same idea in my head, but I was hoping someone will prove me wrong. I never ran it off the cig power, just off the P1900.

Thanks.

I run my tablet off battery most of the time but when battery dies, i have run it off of my AC adapter that i have plugged into my cig. lighter. I haven't had any issues with this. Once the laptop gets charged again, i take the power cord out/unplug the ac inverter from the cig lighter.

for what it's worth my peoples,
- sh00k