Normal thing to do:
Call the battery pack maker, and ask if they can give RMA service even though it just left the warranty period. (they will likely say no, but it does not hurt to ask and be sure.)
If they say yes, do the RMA thing and send them the battery, get new one in the mail in exchange.
If they say no, recycle old battery/dispose of properly, and buy a replacement.
The not normal, but some people do it anyway thing to do:
Disassemble the battery's case very carefully, document the cell types inside, check each one with a digital multimeter to see if they are healthy (above 3.5v), then order replacement cells. When replacement cells arrive, desolder and replace/resolder new cells one at a time into the bundle, reseal the case with contact cement, and charge to 100%.
Further reading:
Lithium Ion battery packs have protection circuitry inside that monitor charge, discharge, and temperature cycle data for each and every cell inside the pack. This circuitry monitors for anomalies during charge or discharge, and then disables the cells if it thinks they are showing signs of defect. This is to prevent the battery pack from catching on fire. (no, really. ON FIRE.) Often, this causes the protection circuitry to disable cells prematurely (maybe the laptop got hot because you used it on a hot train ride or something, and the temperature sensors in the battery pack felt this was dangerous-- etc.), but one can never be certain without extensive forensic testing of the supposed defective cell inside the pack (that cell really COULD be a timebomb waiting to explode in your lap if you charge it). The charge controller does not take chances-- it disables the cell, and never uses it again, does not let it charge, anything. This is most likely what has happened to your battery pack for your laptop, and why it is "charging too fast to 100%" and has "terrible life" now. The few cells still "healthy" in the pack are supplying all the charge to the laptop, because the others are disabled. This is what the blinking charge light is all about-- the laptop realizes that the battery pack is incorrectly reporting 100% charge, and keeps trying to charge the battery. The pack says "Hell no, I am as full as I will allow you to charge me!" and aborts the charge cycle. Rinse, repeat. Rebuilding the pack yourself (not normal option listed above) often can convince the charge controller to re-enable those cells again (after you replace them), and the pack will function normally again afterwards, but this is NOT for the faint of heart, the inexperienced, or the unskilled. The sensible option is to see if the manufacturer will honor a replacement, and depending, replace in the appropriate method.