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A cheap external power pack.

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Forward: I am a poor student, I spend several hours a day in the same lecture hall that has not power outlets.

Problem: My Laptop, currently one year old only lasts about 3 hours on battery. I really need more time, an extra hour if possible.

Possible Solution: I want to build (or buy) and external power pack that can push the run time of my laptop. A new battery would be infinitely more efficient, but that would require a power down change out. If it is cheap enough to build, an external battery that feeds the "AC in" port would be ideal.

-A new battery is $100, getting close to that cost makes a new battery a better
-weight, I am a cyclist, the lower the better. This of course makes cheap lead acid batteries a no-go
-Input is 19V, 3.25 amps DC, Wattage? (I am new at this)
-Laptop's battery is 11.1 volts, 4400mAh / 6Cell
-Size: not a huge issue
-Connector: Don't worry, I've got one
-My skill is, ... limited. I can solder and follow schematics though, I have TAs I can consult as well
-Equipment: Not an Issue

Safety and "You'll Kill Yourself"
-I know the charger will not be grounded, this could be an issue
-I will have to weatherize it a bit
-If I will kill myself please tell me

1. Adapt an existing battery (external)
2. Build a new battery (external) using smaller cells
3. Buy a product and modify it
4. Really long extension cord

So, I am at a loss for the rest, I am new to electronics, but I pick things up quickly.
If anyone has any Ideas on how to do this, or weather it should be done at all, please reply.

Last edited:


Well-Known Member
Most Helpful Member
The easiest would be to buy a battery pack with about 19V output and connect that to the charging port. Some less than 19V would probably work. If you have access to a variable power supply you could determine how low you can go before it doesn't work.

The lightest weight batteries are lithium ion so look for what's available in that type. 2000mAH should give you at least an extra hour. You would also need a specialized charger for those since they are not tolerant of incorrect charging.


Well-Known Member
Two errors here:
If it is cheap enough to build, an external battery that feeds the "AC in" port would be ideal.
-Input is 19V, 3.25 amps DC, Wattage? (I am new at this)
Most laptops doesn't have an AC input but a straight DC input. I assume that's what you mean. Beside, it's far easier to build an 12V to 19V converter than one that makes 110V or 220V AC.

Anyway, here is a schematic.


Super Moderator
I believe this might be what you're looking for:

Walmart.com: iRecharge RPCXL- Universal Rechargeable Battery for Laptop Computers: Computers

I don't have one of these myself, but I think it plugs into the DC power port on your computer (?)
You may be able to find more information on this product simply by googling "universal laptop battery" or the like.
Anyway, you can buy this online for $20 + S&H (link). Also, it appears to be fairly lightweight ;)
Der Strom


Well-Known Member
Most Helpful Member
the best is go to ebay and buy another battery for your laptop, they are about 35-40$ shipped
You missed his comment about not wanting to do a "power down change out".
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