# How much power ?

Discussion in 'Electronic Basics' started by SAH, Feb 4, 2004.

1. ### SAHGuest

I need to purchase a small 12Vdc plugin inverter to run a laptop in my car.
According to the specs on the AC charger, it's max current at 120Vac is
1.5A. When I pick out an inverter, what is the minimum power requirment I
will need ?

2. ### Ian StirlingGuest

If you believe the label, 1.5*120=180w.
I'd be very surprised if any laptop exceeded 100W in real life.

3. ### SAHGuest

Well, it does say 1.5 A max, probably might go that high if the battery was
dead (and charging) and you were using the laptop at the same time,...maybe
?

So I guess I would be safe with a 175 Watt inverter than.

4. ### Ian StirlingGuest

Look at the DC power use of the laptop.
It may be on the bottom.
Multiply this wattage by 1.3, and you should come to a more realistic
AC power.
However, 175W should work just fine.

5. ### JeBGuest

and you might check to see if your computer can use some sort of
120vac to run a battery charger that converts the 120vac back to some dc
voltage to charge the battery.

6. ### SAHGuest

Ya, I hear ya but its only 39.99, I'd be willing to bet that a 12V adapter
for a Compaq laptop will be a shade more than 39.99 going by the way they
fleece you for accessories. Not to mention that I can use the inverter for
other things too, camping, etc....

7. ### David WoodGuest

Wouldn't it be funny if the laptop requires 12VDC and all that's
really needed is one of those nice little curly cords with a fused
lighter plug!?

8. ### Ian StirlingGuest

The problem there is that the car supplies from about -40 to +80V, under
various transient conditions, and from 8-16V with faults that'll
let it run.

9. ### David WoodGuest

The problem there is that the car supplies from about -40 to +80V, under
I've plugged all kinds of electronics into the power in my car with no
problem. I've been told this happens for two reasons: 1, the car
battery acts as a capacitor and 2, the devices have their own
regulators and/or transient suppressors if they're that sensitive.

If you start the car then disconnect the battery and break the voltage
regulator or diode pack you'll get "various transient conditions." Old
cars may run in this condition but I don't care, nothing SAH does to
power his laptop will kill mine;-]