The first laptop I ever owned was a Toshiba CDT1625 and the battery was down to 20 minutes life after about a month. I yelled about it at Toshiba until they sent me a new laptop battery, which was stone dead within a few weeks. Laptop batteries from some manufacturers have notoriously short lifespans (not mentioning any names here:-), and the Ni-MH (Nickel Metal Hydride Battery) which replaced NiCd (Nickel Cadmium) in most applications just aren't that much better. So, I thought I'd crack open the stone dead battery back and see if it could be rebuilt. The first thing I learned is that laptop battery packs aren't built to be rebuilt, they GLUE the things closed. Took some serious prying to get the thing battery pack open, but definitely in reusable condition.
Most newer batteries can't be easily repaired, but I find Amazon has decent pricing on replacements. There isn't a whole lot to an old laptop battery, just a hard plastic shell, enough individual cells to make up the required voltage, and a thermocouple. The black wire scotch-taped between two battery cells is the thermocouple, and it's positioned to measure the air temperature in the battery pack, not the actual battery surface temperature. Maybe that's why the batteries fail so fast. The only other component in the battery pack is the little circuit board (below), which has nothing on it but the contacts for the notebook DC circuitry. Looking at it from the outside, you would have thought there was some fancy charging circuit inside, not so. When you buy a replacement laptop battery, you're just getting a new set of cells to run down.
	The individual cells that make up the laptop battery are simply strapped together with little contact strips which are soldered in place (below). To repair a laptop battery, you need to replace all the cells and resolder, but here's the problem. I searched around for a price on the cells, Sanyo HR-4/3AU, and the best price I could find was over $5. With nine 1.2V cells required to make up the 10.8V battery, I'd need to spend around $50 to replace the cells and have a replacement battery. On the other hand, I can buy a new Toshiba laptop battery for $69.99 without even shopping around, that's the first one that came up in Google. To cost effectively repair a laptop battery, you'd either need to find the replacement cells wholesale, or be doing it for a laptop whose battery is just ridiculously overpriced to start with. Live and learn.