I recently took apart my laptop and upgraded the CPU and added an internal wireless card (mini-PCI). Anyway now I'm looking to rebuild the battery using better power cells but i need some advice. My battery's part number is PA3251U-1BRS, and it says "4300 mAh" which i have gathered means 4300 mili-amp hours. I have also learned online that my pack supposedly has 8 power cells. I was looking at the 'standard' (i haven't opened the battery yet) power cells and the best ones are 2600mAh each (http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2763). I think you add mAh together to get total power, but that would mean my battery would have something like 20,800 mAh (almost FIVE times the power if my battery were new). Is that right? can the circuitry in my battery handle that (ie would it work)? If anyone has had any experience rebuild batteries or knows about electrical engineering I would be very greatful. Thanks!

you're just talking about the parallel voltage equation 1/V + 1/V... So therefore that don't just add up together. see here: http://en.wikipedia.org/wiki/Series_and_parallel_circuits
Can't you just buy another battery?

yes - don't. It's dangerous.Li batteries are quite toxic and NiMH batteries are caustic.

First off, I know about parallel and series circuits seeing as I graduated high school, and no where on that page does it even mention milliamp hours. Try this:
http://en.wikipedia.org/wiki/Ampere-hour
http://www.gws.com.tw/english/service/faq/battery packs.htm
http://www.batteryspecialists.com/mah.htm

And no, 100-150$ for a new laptop battery is not appealing considering thats about what my laptop is worth, and i could potentially DIY for alot less (under 50$ - just google "rebuild laptop battery").

I know its slightly dangerous, but I plan on getting pre-tabbed batteries so I wont be heating the cells at all, and of course i have safety glasses in-case they do explode.

don't forget about controller of the battery. you'll need to reflash the controller for new capacity. tell me, the marking of all chips, or post a picture of the controller.

How would you flash the battery controller? I will post the info as soon as i manage to open it (I dont want to break anything - any advice on how to open it as gently as possible would be great!). Thanks!

personally I cannot see the benefit of building your own batteries. If you think you can do it safely and cheaply, then go for it.

for example: the new battery for Asus A6J(p/n: a42-a2) costs 160-180$ usd. you need 8 li-ion elements(2400 or 2600 mah) they cost 7 dollars per element, and you need to assembly battery pack and renew battery controller. overall cost is 69-70$ + your time. however, laptop batteries are quit hard to disassembly, and there are some controllers which locks permanently without possibility to renew.