possible to design laptop to run on AA batteries

[OS]

My laptop has a LION battery that is rated I think 14.8V, 4.0 A/Hr. 2000 mA/Hr AA batteries are common now, so presumably you can slap together enough AAs to get the voltage/capacity to match or exceed LION batteries.

Why has no one done this, besides the obvious answer of OEMs liking to tie consumers to $150 proprietary batteries?

 

[Varun]

Packaging - you would need between 20 (Alkaline)and 24 (Ni-Cad/Ni-MH) AA batteries to get equal voltage and current capabilities which is much larger than one Li-ion battery pack.

Power - You'll have to dig for some data sheets but I would imagine the discharge curve of the Li-ion battery would be much better, and likely charge faster as well.

 

[Calin]

Volume: you should use 10 AA batteries, which might be much bigger than that battery. Also I don't know if the AA batteries are capable of generating the current needed for the laptop (you can't put them in parallel, just in series), and if they are capable, how much the voltage they supply would decrease.
Edit: A rechargeable battery has output voltage (no load) somewhere at 1.2V. You would need some 12 such batteries to match the output voltage. However, you might need several blocks of batteries to generate the maximum current the laptop needs. Also, batteries in paralel are not a very good idea (as they will discharge at different rates when using current limiters or might close current between them if not using current limiters)

 

[Mark R]

I'm sure it could be done, however, my preference would be not to try to replace the OEM battery, but instead replace the AC adaptor. You can buy super-long life battery packs (usually Li-ion) which work in this way.

Most laptops need 20 V DC input from the mains. Put 14 AA batteries in series, and you'll have a pack that goes from about 16-21 V depending on charge. Stick a suitable connector on it, and you're good to go. NiMH batteries have very good current handling - probably better than Li-ion so should have no probs powering the laptop.

Of course, you won't get battery health status - the laptop will probably just cut out without warning (keep a fully charged OEM battery in it so you get some warning). You are also at very high risk of 'reversing' one or more cells in the pack because of the high voltage, so you could never discharge it very deeply. Additionally, 2 Ah will only get you half the run-time of the stock battery. If you wanted to do it seriously then you'd need industrial grade C cells (or D cells) which can have capacities of up 13 Ah.

You probably couldn't just replace the main battery with an NiMH pack because many modern laptops expect a 'smart' battery. Many laptop battery packs contain a small health monitoring circuit and CPU. The CPU in the battery pack communicates with the laptop reporting health status, charge status, expected run-time, and sending requests for charging, etc. If the laptop doesn't detect a suitable monitoring circuit then you probably won't get a charge status, won't be able to charge, etc.

 

[Jeff7]

Originally posted by: Varun
Packaging - you would need between 20 (Alkaline)and 24 (Ni-Cad/Ni-MH) AA batteries to get equal voltage and current capabilities which is much larger than one Li-ion battery pack.

Power - You'll have to dig for some data sheets but I would imagine the discharge curve of the Li-ion battery would be much better, and likely charge faster as well.

Lithium ion batteries are used because they have a higher energy density than anything else. They are more difficult to use - discharge them too much, and they won't charge again; overcharge them just a little bit too much, and you'll either damage them or cause a fire. And they're expensive. But those negatives aside, they get people closer to the long run-times and small sizes that they're looking for.
Battery technology still lags far behind portable technology's growing power demands.


So heck, maybe you could plug the laptop into a 12V lead-acid battery with a high-power DC-DC voltage booster to give you the output you want. But then instead of being tied to proprietary batteries (not much in laptops isn't proprietary anyway) you'd be tied to a large, heavy battery and a heat-generating voltage converter. Alternately, you could seek out individual lead-acid cells, and wire them in series for 14VDC, which your laptop might be able to live with.
All that said, if you try this with a 40 amp battery and wind up melting a portion of your laptop, don't blame me.


And besides, it'd probably be easier to just skip feeding voltage to the potentially sensitive battery charging circuit, and give it right to the main DC input that comes from the power brick.

 

[VigilanteCS]

It wont be long before we have batteries that will hold a charge for a few years.

 

[Calin]

We have batteries that hold the charge for several years. Too bad they aren't rechargeable

 

[Jeff7]

Originally posted by: Calin
We have batteries that hold the charge for several years. Too bad they aren't rechargeable

Yup. Regular lithium batteries. Some of them have shelf lives of at least 10 years.

Be nice if we could also get REALLY high capacity batteries though, even if they didn't have long shelf lives.
It'd be great if you could just store raw electrons. A pound of electrons should be enough to power a house for a few years - of course, it'd probably take up the space of a single atom, if that, and if the power were accidentally released all at once, there'd be a massive lightning bolt, and maybe a bit of the house left. I calculated all this some time ago; some reason, 48 megawatts comes to mind.

 

[Valkerie]

The thing why a lot of companies have common sense not to publicly sell non-rechargable batteries, is because who would buy them in the first place? Not very many. Secondly, if they did start selling non rechargable batteries, how many people could actually afford it?

 

[Tenshodo]

Now I hear we have nuculear batteries

Not sure if its Completely trustable but interesting nonetheless
http://www.spectrum.ieee.org/WEBONLY/publicfeature/sep04/0904nuc.html

if this tech gets perfected, think of the possiblilities