# Thread: Can a P4 e-PC be powered by a cigarette lighter power?

1. ## Can a P4 e-PC be powered by a cigarette lighter power?

I have just bought a P4 1.6 GHz HP e-PC which uses an external power adapter which puts out both 12V (7650 mA) and / or 19V (2800 mA).

I am keen to use a laptop power source to power it - I know it can be done with the older e-PCs (Pentium III) which had a laptop style input socket - but this computer has a square pin with 4 leads - 12V, 19V, PGOOD and SHIELD.

Has anyone been successful in using a DC-DC / cigarette lighter adapter (or 2?) in supplying this computer with power - or do I have to get an inverter?

Any help would be greatly appreciated!

2. Carnetix psu can supply 2 voltage 12v and 19v I think... check the store....

3. ## Do the math or use a meter...

Just because the adaptor puts out 7650mA@12V and 2800mA@19V doesn't necessarily mean that the system will actually draw that much power. But still, it's safe to assume that it might. Let's convert that to watts:

7.650A * 12V = 91.8W

2.800 * 19V = 53.2W

That's a total of roughly 145 watts. Figure that the power supply is going to be at best 90% efficient and you're looking at about 160 watts. Most cigarette plugs are capable of no more than 100W, so you're certainly looking at the potential for problems there.

Another approach is to put a meter in-line with the 12V and 19V lines and see what the thing is actually drawing under load. Work these numbers back and see if you are within the specs of your car's cigarette circuit. If you are planning to use an invertor instead of a DC-DC supply, things are even more difficult mathematically as invertors vary greatly in efficiency. The best thing to do here is to wire the whole rig directly to the battery with a meter in-line to measure actual power requirements.

As an aside, when you make your measurements, be sure to be running some benchmarking software on your PC that will be driving the CPU and hard disk fully to get a worst-case power measurement. There is quite a bit of difference there, and if you aren't careful it is quite possible to blow a breaker under heavy CPU load.

-p.

4. Thank you very much for your ideas.

I'll try them soon and let you know how it goes...

5. I have been reading a lot more since I asked the question.

It doesn't look too good

The only thing that comes close is the P1900 Carnetix but the secondary output for that puts nowhere near the 7650mA that the adapter is rated at (and that I presume the computer draws).

I would like to get the power with DC-DC and some kind of ignition protection... I see my options as getting 2 Carnetix - 1900 and 1290 (hopefully the 12V 6300mA that this puts out is adequate) - which is somewhat expensive...

or wiring 2 separate laptop car DC adaptors - a 12V and a 19V to the cigarette lighter (or directly to the battery if it is likely to overload the circuit)

or getting an inverter - are there any risks of damage to the computer with an inverter? What is the advantage of a pure sine wave inverter as opposed to a modified sine wave inverter?

or throw the frigging e-PC in the fire

Sorry for being a noob - but - I am and I like icons

6. cigerette lighters in most cars no a days wont pull much more than 150watt

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