How it is possible to power up a 12V device using only 5V?

I had a power outage some time ago, and needed to use the internet for university search. i was with my notebook, EEEPC 1000H with 4 hours of batt. my internet is over a cable and it uses 12V for power; i had a cable for my external dvd reader (ad/dc pin to USB)that fitted into the modem, and i plugged it into my usb. it worked very well. however, the notebook started to heat up slowly, and the battery indicator dropped from 4:00 to 2:00; this was safe to do? could it damaged my notebook? how can be possible 12V into 5V?

finky5558 years ago
Can your 5v supply output the current you would need to boost the 5v to 12v? As an example to draw 2 amps at 12v would require the 5v supply to deliver about 5 amps. That is quite a lot. My laptop draws much more than that, 19v at up to 3.5 amps. Even a UPS would have to be very hefty to power you for 4 hours, cost would be very high. One solution would be to use 3 x 6v 10 A/H batteries with this unit http://www.trcelectronics.com/Meanwell/sd-50a-12.shtml which would give you your 12 volts at the time you need. You would have to figure out how to charge them safely to keep them ready between power fails.
Shiron (author) 8 years ago
@finky555 I dunno if it can :P i think that it could somehow; the most strange is that the modem worked really well on 5V, but the notebook was heating :P
Putzer8 years ago
Regardless of the voltage it would still be getting power from a 5 volt, 12 volt or 2 volt. However, it wouldn't be the optimal amount needed to operate efficiently and the amperage is most likely different. Heat is a byproduct of resistance so it isn't advisable to do this unless it is desperately needed or you have spare notebooks lying around.