I would like to design and build a DC-DC converter with following specifications.
Input : 12VDC 7Ah from ups deep-cycle battery
Output:19VDC 3A to a laptop.
How can i setup the DC battery voltage supply system so that i can have it running for at least 12 hours without recharging?
youll loose lots of effort to build this
lots of cash
and lots of time
my advice but its just me
its madness to add 2volts to a given voltage
when mostly a laptop will run fine from 17v dc
i must mention the cpu in your laptop uses 3.3v the logic 5v
and the display is the only thing that needs around 15-19v
i recon you need to do nothing
and just turn up the brightness of the display to compinsate for the loss of 2volts {about 20% increase in brightness level {most laptop video chipset come with an applet to adjust this level}
as youll find the backlight inverter is what asks for 19v not the laptop and its happy as long as it backlights enough
dont be daft !!!
but too add 5V its far easier to add a 6V cell and a diode to drop it back to 19v total
You will need a DC/DC converter like the one in this link
Unfortunately a 12V/7Ah battery will be not enough to power your laptop for about 12 hours.
Let's assume your laptop will require 3A at 19V: it is 57Wh. Multiplied for 12 hours it will be 684W/12h
Your 12V battery capacity is 84Wh, so assuming an efficiency of 90% of your DC/DC converter, you will need at least a battery with a 9 times the 7Ah capacity.
i was thinking, if i were to arrange
three 12VDC 7Ah batteries in series
would i get the power supply to last longer?
i am not sure wether its series or parallel connection
that makes it work.
But if its possible to get up to 2-3 hours from
a 12VDC battery supplying current of 3A
then if i connect that battery with two other
batteries of the same type, can i get at least
(3x2hours) 6 hours of current supply?