DC===>AC Power Problem

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

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

 

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.

 

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*

 

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.

 

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 nothing.

 

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.

 

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

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

Ken@Japan

 

<div class='quotetop'>QUOTE(ekpolk @ Mar 6 2007, 09:14 PM) [snapback]401412[/snapback]</div>

Ekpolk,

I think your numbers do not sound correct to me. You state that your Targus is good to 10 amps! For any inverter to be able to put a continous 10 amps at 120 volts would require an inverter rated at 1200 watts continous and about 2400 surge capacity!!! The formula when working with inverters is this:

P=IE or Power (watts) = Current (amps) x Voltage (volts) so using your 10 amp numbers:

watts = 10amp x 120 volts so watts = 1200 watts. This is a sizeable inverter and could not be powered by the 12 volt socket in the Prius but would need very heavy guage fused wire direct to the battery!!

Let's look at your example now.


If your laptop brick requires a continous 1.6 amps then lets see what you do need.

P=IE

Power in watts = 1.6 amps x 120 volts or about 192 watts continous.

Well, I know nothing about the "Targus" inverter but I did a simple search on Amazon.com for them and see they have several list and they all range 90 watts to 150 watts max!!! This is too small an inverter for your laptop brick thus it is being overloaded, not overheated.

You need about 200 watts continous so I would look for about a 400 inverter to handle any surges. These are easily bought on Ebay for about $20-25 range.

I hope this helps! Best wishes.

Tom - KN6VV

 

<div class='quotetop'>QUOTE(ken1784 @ Mar 6 2007, 11:51 PM) [snapback]401436[/snapback]</div>

I thought they said 65W at 19V, but either way, the inverter seems too small for that load.

 

I've used iGo power adapters and found them really useful. AC->DC and DC->DC at several wattages, AC input plugs for US, Europe, and Asia, cars and some airplanes, plus you can charge your phone while you charge your laptop.

If only they would make a mag-latch for Mac notebooks...

 

<div class='quotetop'>QUOTE(ekpolk @ Mar 6 2007, 10:14 PM) [snapback]401412[/snapback]</div>

If you have a power strip and an inexpensive DVM with an AC scale, you could plug the power strip into the Targus and read the unloaded 'average' VAC. Then plug in the laptop power brick into a second outlet and measure the 'average' VAC. This will give an idea of what sort of loading is happening to the Targus. You might measure both 'sleep' and 'powered' mode. One mitigation strategy might be to tune some of the power parameters of the laptop to minimize power load if it is 'on the margin.' Regardless, this would also be an excellent way to qualify any replacement DC-to-AC converter until you find one that works.

Bob Wilson

 

<div class='quotetop'>QUOTE(ekpolk @ Mar 6 2007, 11:14 PM) [snapback]401412[/snapback]</div>

EKPolk,

The reason that it doesn't get hot is that its not operating.

The 10 amps is at 12 (13.6) volts DC. This is about 130 watts in and the Targus inverter can generate about 90 watts continuous at 120 volts which is not bad performance. Your Gateway brick needs 1.6 amps at 120 volts which is, as was stated by others, 192 watts so the Targus shuts down (this may only be a startup surge current). Note that your problem is the low quality of the Gateway brick. If the specs are correct, it has a very low efficiency (about 35%, 192w in - 65w out) which requires you to buy a higher capacity inverter.

If you plug the Targus into the 12v first to get it started and then plug in the Gateway brick without turning on the laptop. You may be able to get everything working. It's often the startup surge current that prevents the supplies from operating. I have this same problem with the 12v brick (using AC mains) for my thermoelectric cooler and starting it first allows it to work.

JeffD

 

<div class='quotetop'>QUOTE(jdenenberg @ Mar 8 2007, 08:26 AM) [snapback]402193[/snapback]</div>

On other option is to get an 'in-rush' thermistor and see if it can tame the power brick. I think Radio Shack has them for a dollar or so. WARNING: 'in-rush' thermistors work properly by getting warm. If you use one, make sure it is in a place so it wont burn or hurt someone.

Bob Wilson