My latest project is to replace the battery out of my old laptop. It's been in desperate need of a revamp for longer than I can remember.

The current battery is a 9.6v 3.5Ah made up of the usual multitude of batteries.

Is there a method for changing the current batteries which are 1.2v 3.5aH 'AA' sized batteries with more 'common' 1.5v 3.5aH rechargeable batteries?

I've read it being done with the battery pack 1.2v batteries, but at $8.50 a battery and having 8 batteries in the pack it turns out to be an expensive exercise. I can purchase 1.5v 3.5aH batteries for $1.85 a piece. Is there a way to use these?

 

1.5V rechargeable cells more common than 1.2V? This would be a surprise to me; better check your sources again. What's the chemistry of the 1.5V rechargeable?

 

They're both NiMH

 

Where do you get 1.5V NiMH???

 

Ni-MH cells are nominally 1.2V the same as old Ni-Cad cells.
The cells are 1.5V for a moment when charged at a high current.
9.6V is eight 1.2V cells.

Energizer has AA Ni-MH cells with a 2500mAh rating. I don't think any manufacturer makes them 3.5Ah.

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Uncle $crooge

 

Oh, don't mind me. I was reading two different things and not making much sense of either.
Should stop reading when I'm half asleep.

The original batteries that came out of it -> 8 x 3500maH

The ones I can buy are 2500maH. I guess they will go in there no problem, but just have less runtime.

It's a strange feeling to answer your own question.

 

I f you get access to an old laptop battery and rip and analyse, you will perhaps appreciate that there are lot more than just Number of cells in series. A lot more really. please checkout this aspect, before you really go for an improvised arrangement. these may include cell temp monitoring , and many facilites. Same is the case with Cellphone batteries even.

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Regards,
Sarma.

 

New laptop computers have lightweight and high capacity Lithium batteries, not heavy Ni-MH cells. The cells are larger than AA and are welded together. Since Lithium is very dangerous, the battery has a circuit in it that detects voltage, current and temperature.
A Lithium battery cell charges at 4.2V each and slowly discharge to about 3.0V.

My daughter had a Pentium1 laptop. it had a very heavy Ni-Cad battery with many unusual shaped cells.

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Uncle $crooge

 

I have taken this battery pack apart and the cells inside are just in series. Nothing special.

The batteries inside the cells are indeed larger than the normal AA batteries, although they're still rated at the stated 1.2v 3500maH. There's no circuitry inside which I think will make this change over simple. They're just an interface onto which the 'final' battery terminals are soldered and slots into the laptop.

 

You will need to re-design the charger so it doesn't over-charge the lower-capacity AA cells.
The old charging circuit might have a temperature sensor on one battery cell to detect full charge.

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Uncle $crooge

 

Nice Finding ScuzZ. Now the issue is simple
only issue , you have to replace with same capacity if the charger has to support you as already elaborated by AudioGURU.

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Regards,
Sarma.