Laptop power questions

funkd · 03-29-2009, 07:25 AM

1. Let say, I have install a 300w inverter directly to my battery (with relay), and plug in a laptop AC adapter (70w), will it damage my power supply/laptop?

2. Is it recommended to connect a powerboard to the inverter to power other electrical goods such as, powered usb hub, monitor etc?

The inverter: http://jaycar.com.au/productView.asp...T&SUBCATID=680

I appreciate the help!

Bugbyte · 03-29-2009, 03:21 PM

No. Using an inverter that is 300 watts to power something that needs only 70 watts will not hurt the 70 watt device. The inverter will only supply what is needed by the devices plugged in. It will not "push" 300 watts through it.

I don't know what you mean by 'powerboard'. Do you mean a power strip?

funkd · 03-30-2009, 04:24 AM

Awesome, thanks for that!

And yes, power strip would I be able to use one - is it recommended?

Thanks for you help!

NSFW · 03-31-2009, 04:29 AM

I'm using an inverter for my laptop CarPC, I think it's only 100 watts but that's plenty. I am using two passive (powered by the laptop) USB hubs, so the laptop's power supply just plugs directly into the inverter.

I am looking for a way to use a powered USB hub, but I'd rather do that without running more 120v wiring through my car. You could use a power strip but it seems like a waste of space, and a waste of power. On the other hand I am still looking for 12v power for a bigger USB hub so I haven't got a much better idea...

My touchscreen uses 12v power, so it's powered from (what used to be) the cigarette lighter circuit.

merlin12volt · 04-01-2009, 11:53 PM

Since your powered hub does nothing more then supply 5vdc to one pin and ground to the other, it would stand to reason that you could get one of these http://www.dealextreme.com/details.dx/sku.688 a usb to usb cable and a 12volt cigarette adapter to hardwire since I know you said that the screen uses the cigarette lighter.

There is another way to go about this by building a simple voltage regulator circuit, but odds are, if you are asking this question, you probably either know nothing about that or aren't interested.

Either way hope this helps.

NSFW · 04-02-2009, 02:12 AM

Actually I bought something very similar, cracked it open to get rid of the cigarette lighter plug, soldered in some wires, spliced those into my cigarette lighter circuit... and had no luck. The USB hub just stopped working when I connected my hacked power supply.

I probably screwed something up. But at that point I wanted my car back (was working on another under-dash project at the same time) so I just went back to my passive 4-port hub rather than trying to diagnose what went wrong with my hacked power supply.

Someone here was working on a purpose-built USB power supply but I lost track of that thread. Time to search...