Re: Inverter power needed for Laptop (charger) in car



mike wrote:
> news.rcn.com wrote:
> > Either there is something obvious here I can't see or I have one of the
> > worst cases of dry joints in recorded history
> >
> > I am trying to use a laptop in a car. I have an inverter rated at 50w. It
> > worked for a few months and then peremptorily stopped with a sudden rattle
> > from within and no light going on to show that it is ready. When I opened it
> > up I found a whole power transistor rattling around inside with all three
> > joints seemingly not connected and the glue from the rear of the transistor
> > seemingly having come off. Curiously the ends of the connectors don't
> > actually look as if they were ever connected?? (The holes on them from the
> > motherboard do look as if at least something was once connected to them as
> > they are filled with slightly disturbed-looking solder)
> >
> > Is this just a lousy joint on some cheap chinese-looking inverter which
> > worked while the pin ends merely touched the mainboard slightly or does the
> > power charger need SUBSTANTIALLY more than a puny 50 watts to work: The
> > charger reports that it needs an input of from 100 to 250 volts at 1.5 amps
> > to give an output of 18.5 volts at 2.7 amps. Can someone do the maths for me
> > and let me know what power inverter this charger will need please?
> >
> > I am suspicious of the puny nature of the inverter because although I can't
> > see a laptop using all that much power, I have also got a huge heavy duty
> > Coleman PMP400 inverter with fins all over the place and a heavy duty
> > sounding onboard fan rated at 400 watts (peak surge 800 watts at 3.5 amps)
> > and after about ten minutes of use, IT starts to overload on this laptop
> > charger (meaning the red warning light comes on and the inverter starts
> > giving symptoms of blowing): The red light won't now go off: I am wondering
> > if I have blown this inverter as well? (Curiously it didnt last as long as
> > the 50 watt one).
You have other choices besides an inverter.
A DC to DC converter that takes in 12 volts and puts out 15 volts with
a plug soldered onto it that fits the back of your computer would work
a lot more efficiently than an inverter into a power supply.
Also, you can run a laptop directly off a car battery. Just make a
cable with a cigarette lighter plug on one end and a plug for you
computer on the other end. That's how I run my computer in the car.
Your laptop's battery won't recharge from a 12 volt supply, but you
won't be using the laptop's battery anyway. Why not keep it simple --
no inverter or anything, just a cable with a plug on each end.
What's more, your computer might even charge plugged directly into the
cigarette lighter if you are driving the car, because your car's
voltage will be between 14 and 15 volts when you are driving.
I don't use my computer when the car is running because I want to
protect it from the hash on the car's power circuits. But I would have
it plugged in to the cigarette lighter with the car running so it would
charge, as long as the computer is actually turned off. I'm to lazy to
put a filter on the cable I made, or I could use the computer with the
car running.

.

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