I have a problem with my laptop, it is Acer 4740G, suddenly the battery can't charge pass 80%, I bought it 1.5 years ago, and contacted Acer about this problem, they just quoted service & labour charge which is over $100, battery cost not included..
anyone know how to solve this problem (if possible)?
Your battery is old that's the problem. You can recondition it and that might reset the value, but it won't be like new. To recondition it you need to let the battery drain completely and have the comp shut down on its own and then reboot the comp after the battery has a full charge again. At least I think that's how its done, do a search on it if you have questions.
Do not fully drain lithium ion battery. Fully drained cell will reverse polarity as safety precaution, the battery protector circuit will short and your battery becomes boat anchor. Just drain it enough until window hibernates and recharge to see if battery recalibrate. If it doesn't, download CPUID HWmonitor and check your battery wear level. 1.5 years with 20% wear is reasonable if you use the battery.