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I just bought a power inverter for the car (converts the cigarette plug DC to AC for plugging in small items, such as PS2's or laptops, etc.).
Output is rated at 90 watts: 120 V(AC), 60 Hz.
Input is of course of 10.8-15.8 V(DC), 10 A max.

Now I bought it for a lot of reasons, but primarily to use my PowerBook when on the road. The PowerBook's AC/DC transformer adapter is rated at:
Input: 100-240 V(AC); 50/60 Hz, 1.5 A
Output: 24.5 V(DC); 2.65 A

The adapter also mentions "65 W" which I take to mean its output wattage. ("Apple 65W Portable Power Adapter")

My dad has reservations about it being safe to use with the power inverter, as the wattage it is able to input up to is greater than the output wattage of the inverter. Would this be safe to use, or would the power draw pop either the surge protector built into the inverter, or worse, a fuse from the Contour or from the PowerBook's adapter? I would like to go and get a direct DC adapter for the computer to avoid this DC-to-AC-to-DC mess, but I'm not about to spend $79 for one and the inverter ($34 after discount) is far more versatile.

Thanks!

You should be just dandy. But rather then go to all that hassle there are direct dc-dc converters out there (auto/airline adapters) that just skip that whole nasty inversion process. The way to go IMHO.

Looks like it would draw a max of 150 watts. I suspect the max current on the brick would be at the minimum voltage which is listed at 100VAC. So the rated current is 1.5A, therefore this thing could draw 150W of power to produce the 65W output.

So I would look at a 200W + inverter to run your laptop.

FWIW,

TB

They usually overrate the current draw for electrical appliances by a factor of two.

Your inverter most likely has overload protection, so if it's not going to work, it won't hurt anything to try it.

If you do need a new inverter Home Depot has some good deals on them (in the tool aisle).

Thanks .... I'm going to try it out (one of these days, lol!) and if it surges then obviously I'll return it.

Tony, your rationalization was exactly what my dad was thinking, although he didn't know that they sold better ones. I looked on eBay and for only slightly more than what I paid for mine (even with employee discount!), I could have 200 or more watts of power. I will definitely look further into that if this doesn't work. I'm almost contemplating returning it immediately without even opening it due to the deals I've seen for "better" models. However at the same time this one is extremely versatile (airplane compatable, built to fit cupholder, has both a DC and AC plug, etc.).

... decisions, decisions ...

Oh, one other thing--the brick is a switching power supply and they are typically 80 to 90% efficient, from what I recall. The only way it'd consume 150W to put put 65W is if it were a linear power supply, and I guarantee it's not because it'd weigh about 15 pounds and be the size of a shoebox if it were. Well, that's an exaggeration, but it'd be big.

It's probably rated at 1.5A because I believe it will intially draw a bunch of current when it is first plugged in as it is is just a big coil (an inductive load) and as the field is built up in the coil the current demand will drop.

Of course I reserve the right to be wrong, it's been a long time since the mid-80's so I may have forgotten how this stuff all works or they may have changed the rules, LOL.

TB

Even if that's the case it should be OK, most power inverters are rated x watts continuous, x times 2 watts peak.

So my 400 watt inverter can handle up to an 800 watt startup surge.