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Old 23rd April 2008, 12:11 AM   #1
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Default Rising DC voltage

Hi,

is there any simple way to rise DC voltage by a few 10th of volts?

I sometimes run my laptop from a 12v SLA battery, using a car/home laptop power adapter.

I can get about 2.5 hours from a 7Ah SLA battery, but I should be able to run it for at least 4 hours, considering the original LiIon 4Ah battery (now lasts 20minutes) originally worked for 2.5 hours.

I'm under the impression that it's caused by the fact that the adapter runs from a minimum DC voltage of 11.75V, and that the battery is supposed to be empty at about 11.4V.

Would there be a simple way to rise the voltage a bit to get a few extra hours out of the battery?
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Old 23rd April 2008, 12:23 AM   #2
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Erm,Not really..

I suppose you could make a SMPS that took a 10-13V input,and output a regulated 11.75V or whatever voltage is required. It may not be the most efficient SMPS ever,but might be do-able.

Can you reduce the load at all? Any unused hardware connected?
Remove any PCMCIA and USB devices when they are not in use.

Perhaps stick a flexible solar panel on the back of the screen? It could trickle the charge the battery a bit,would give you a bit more runtime,and help keep the battery voltage up a tad bit more?
(Flexible) solar panels are kind of expensive,so this may not be very practical.

Edit:
One other thought,If you are using wires to connect the battery to the laptop,you could try bumping them up (down,really) a few sizes.
Heavier wire will have less resistance (loss) and you might gain a bit of voltage,if your wires are really small.
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Old 23rd April 2008, 01:58 AM   #3
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I guess you could make a SMPS that takes 12 Volt input and provide only a few millivolts at the output, and connect it in series with the battery?
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Old 23rd April 2008, 02:36 AM   #4
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Make a simple dc-dc powersupply that gets 24V, then regulate down to about 13-14v your choice, that way you are sure to have enough voltage.

Any 12V push-pull smps primary always has 24v on it. You could get a cheap toroid choke, wrap just 10+10 turns of thick wire, do push pull and get the 24V. No secondary winding needed.
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Old 24th April 2008, 03:55 PM   #5
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Quote:
Originally posted by EWorkshop1708
Make a simple dc-dc powersupply that gets 24V, then regulate down to about 13-14v your choice, that way you are sure to have enough voltage.....
What DragonMaster wanted was to extend the operating time of his power supply.
If he doubles the voltage and then regulates it down, will surely half the capacity.
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