DC===>AC Power Problem

[ekpolk]

Hello everyone. I’ve been traveling a bunch, and haven’t visited here much. I’m looking forward to being back more often.

Related to my travels, I’ve been lugging my computer around with me, pretty much out of necessity. In an attempt to increase my flexibility, I bought a Targus cigarette lighter inverter that converts the car’s DC power to ~110v AC.

Or at least it tries. . .

Actually, it works for maybe a half hour or so, and then the little Targus unit seems to shut itself off, while generating a warning tone. I can not detect any gross overheat, at least not by feeling the outside of the unit, or by smelling for an overtemp odor. Then it takes about two hours before it will work again. In my insufficiently educated mind, that would seem to suggest overheating, but again no overt symptoms of that.

I happen to use a radar detector, and I have it set so that it’s default baseline display is the car’s DC voltage level. With the car in READY mode, it always reads a dead steady 13.8v, and the use of the Targus inverter unit does not seem to impact this. So I assume that the output from the car’s DC system is correct.

What am I missing? Is there something about the Prius’ electrical system that would cause a problem with using a plug-in inverter? I don’t think the inverter is the problem, as it seems to work OK in our other car (an 07 Avalon). And plugging a laptop’s charger would not seem to be an overwhelming load (no, I haven’t tried to run hairdryers or space heaters...).

Anyone got any thoughts? TIA.

[bwilson4web]

<div class='quotetop'>QUOTE(ekpolk @ Mar 6 2007, 02:08 PM) [snapback]401077[/snapback]</div>

Hello everyone. I’ve been traveling a bunch, and haven’t visited here much. I’m looking forward to being back more often.

Related to my travels, I’ve been lugging my computer around with me, pretty much out of necessity. In an attempt to increase my flexibility, I bought a Targus cigarette lighter inverter that converts the car’s DC power to ~110v AC.

Or at least it tries. . .

Actually, it works for maybe a half hour or so, and then the little Targus unit seems to shut itself off, while generating a warning tone. . . .[/b]

What is the AC power rating of the Targus?
What is the AC power rating of the laptop?

The cigarette lighter is fused, if I remember correctly, for either 12A or 15A. It may be rated at 12A but blow at 15A. Regardless, if the cigarette lighter source were the problem, since it is fused, it would be binary: ON or blown.

IMHO, it sounds like the Targus is being overloaded by the laptop. Also, there is a risk that the Targus inverter circuit may be generating a signal that doesn't work well with the laptop 'power brick'. The possibilities are endless but I would first look at the Targus specs vs. laptop power brick.

BTW, what is the output voltage of the power brick? If it is say 12VDC, you may have a much easier solution at hand.

Bob Wilson

[Sho-Bud]

I bought a converter some time ago, it was rated at 150 watts. However, my laptop needs more than that, and the internal safety-switch of the converter would shutt it off.
My guess is that the same thing is happening to you, no problem on the Prius side, but you may need a heavier converter.

[hobbit]

It's odd that a laptop would need any more than maybe 3 amps at
12V, or the 2 or thereabouts it takes in at 18V when the brick is
plugged in. I run my aged Thinkpad *directly* off the car's 12 or
14 volts [depending on state], using the rewired carcass of an old
battery pack, and it works fine. Laptops are kind of funny, of
course -- the less voltage you feed them, the *more* current they
draw. But none of this should be a problem, unless you've got some
really serious conversion losses in the inverter --> brick combination
and you're really wafting away the extra 100 watts as heat.
.
Did the Targus thingie feel excessively warm?
.
_H*

[DFWPrius]

Have you tried auto/airline converter for your laptop, plugs into the 12DCV outlet.
You can use it in the Prius and on aircraft when you fly.

[ekpolk]

Guys:

Thanks for the quick replies. The brick for the laptop (a Gateway) says the output is 19V (alas, no, not 12)and it's 65W. The Targus unit claims to put out 90W of 120V 60 cycle AC. Based upon that, you'd think it would work, but who knows...

I guess the next step is to look for either a direct DC converter (making DC into AC so I can make more DC does seem a little Rube Goldberg...) or if I have to, a beefier version of what I've already got.

[tochatihu]

If the Targus is making modified sine wave AC, there is a chance that your computer's digital switching power supply is not happy about that.
That it works OK in the other car does not buttress my idea however.

If the Targus claims to be 'pure sine wave', then I got nuttin.

[ekpolk]

<div class='quotetop'>QUOTE(hobbit @ Mar 6 2007, 04:24 PM) [snapback]401219[/snapback]</div>

It's odd that a laptop would need any more than maybe 3 amps at
12V, or the 2 or thereabouts it takes in at 18V when the brick is
plugged in. I run my aged Thinkpad *directly* off the car's 12 or
14 volts [depending on state], using the rewired carcass of an old
battery pack, and it works fine. Laptops are kind of funny, of
course -- the less voltage you feed them, the *more* current they
draw. But none of this should be a problem, unless you've got some
really serious conversion losses in the inverter --> brick combination
and you're really wafting away the extra 100 watts as heat.
.
Did the Targus thingie feel excessively warm?
.
_H*
[/b]

Hobbit:

No, none of it seems to make sense. It's not hot to the touch, and doesn't have any of that tell-tale smell of something electrical getting too hot. Back of brick says INPUT is 1.6A, with a DC OUTPUT of 3.42A, again, 19V. This Targus unit is supposed to be good for 10A. . .

[Beryl Octet]

The 90 watt unit is too small for a modern laptop. The unit is probably overheating or sensing some overload and shutting down. 90 watts at 110 volts is what, less than an amp, and your charger is wanting 3.4 if I am doing the math right. Spend the money and get a 300 watt unit.

[ken1784]

<div class='quotetop'>QUOTE(ekpolk @ Mar 7 2007, 01:14 PM) [snapback]401412[/snapback]</div>

Back of brick says INPUT is 1.6A, with a DC OUTPUT of 3.42A, again, 19V. This Targus unit is supposed to be good for 10A. . .
[/b]

It looks your brick input is 192W (120V X 1.6A) and your Targus supports only 90W of 120V.

Ken@Japan