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Help with external laptop battery project?

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Kanuck

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I've just found a source for dirt-cheap new rechargeable batteries, which has inspired me to build an external battery for my laptop. My electronics background is just enough to have me doing installations in cars. I have decent soldering skills and am relatively handy. Still, when it comes to building this, I'll need some help... please. :)

Here's what I have:

Laptop AC charger output(DC):
19.5V, 3.34A, 65W

Laptop Battery output (9cell):
11.1V, 85W
(my math says 7.7A)

New Cells:
Li-Ion Polymer
3.7V
3300mAh
Square (won't fit in existing battery case)

My goal is to build a battery that will power my laptop as long as possible while still being small enough to fit reasonably in a backpack. Here are the options I've come up with:

Option A:
External pack, plugs into laptop charging port.
5 cells in series x 2 parallel = 10 cells, 18.5V, 122W
Questions: What do I need to charge this set up? Would I be able to use my existing AC charger? I assume I'd need to add some sort of charge controller to do so? What would I be looking for? Where?

Option B:
External pack, plugs into existing battery connector on laptop.
3 cells in series x 3 parallel = 9 cells, 11.1V, 110W
If Option A proves to be beyond my skills, then the idea is to rip apart my existing battery and salvage its connector and charge controller. I'd rather not, since it's still good for an hour's use, but I imagine it would solve both my connection and charging concerns... I think. Would it?

Any input, including alternatives I haven't thought of, would be appreciated.

Thanks in advance!
 

I think the item you require is in-car dc-dc converter (12V to 19V).
It is sold in computer shop & used to charge Laptop in a vehicle.
If you're thinking of building one yourself there's quite a number of projects available in the Net.
One using the MC34063 or the TL494 are quite common.
 

Your laptop should have a 3.7v battery in sets of 3 batteries in series
so a total of 11.1v

You need to use the same logic

but you can increase the no of sets in parallel to increase the wattage

the on board charger thought the battery terminals should work if you change it from a 6cell to a 9 cell

any thing more might fry the charger circuit

3 cells in series x 3 parallel = 9 cells, 11.1V is best

the idea is to rip apart the existing battery and study the connector and charge controller
create a separate battery bank that has a switch over (Toggle) that uses the same charging circuit on the existing battery but can charge and use the main batteries or charge and use the battery bank

with a small external connector to battery bank

more ideas:

connect a small set of portable speakers to the battery bank chassis to use the same battery and add value and shape to your battery bank.

it works...
:D
 

Kanuck said:
I've just found a source for dirt-cheap new rechargeable batteries, which has inspired me to build an external battery for my laptop. My electronics background is just enough to have me doing installations in cars. I have decent soldering skills and am relatively handy. Still, when it comes to building this, I'll need some help... please. :)

Here's what I have:

Laptop AC charger output(DC):
19.5V, 3.34A, 65W

Laptop Battery output (9cell):
11.1V, 85W
(my math says 7.7A)

New Cells:
Li-Ion Polymer
3.7V
3300mAh
Square (won't fit in existing battery case)

My goal is to build a battery that will power my laptop as long as possible while still being small enough to fit reasonably in a backpack. Here are the options I've come up with:

Option A:
External pack, plugs into laptop charging port.
5 cells in series x 2 parallel = 10 cells, 18.5V, 122W
Questions: What do I need to charge this set up? Would I be able to use my existing AC charger? I assume I'd need to add some sort of charge controller to do so? What would I be looking for? Where?

Option B:
External pack, plugs into existing battery connector on laptop.
3 cells in series x 3 parallel = 9 cells, 11.1V, 110W
If Option A proves to be beyond my skills, then the idea is to rip apart my existing battery and salvage its connector and charge controller. I'd rather not, since it's still good for an hour's use, but I imagine it would solve both my connection and charging concerns... I think. Would it?

Any input, including alternatives I haven't thought of, would be appreciated.

Thanks in advance!
Click to expand...

actually there is a controller in the laptop that communicates with the laptop via SMbus and records it in the meemory. the memory is of EPROM type. open the battery without removing cells and see which ic is there in the circuit. it would be 48pin qfn package or 24 pin BQ series. tell me that and till then do nothing..
i am also working on laptop batteries.
 

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