laptop questions

i just bought a laptop used on ebay, and when it arrived, not suprisingly the battery was dead.  so i have a few questions now...

what should i do about getting a new battery?  the batteries i see for sale are really expensive.  do i actually have to pay that much to get a working battery?

if i get a car charger for my laptop, how long can i sit in my parked car and use my laptop before it kills my car battery?

not long to kill the car battery and yes usually batteries are expensive..

Yes, you have to pay that much for a new battery. Sucks, but that's life. A laptop battery has a capacity of about 4-5A·h (Amp hours), while a car battery is 200+, so you won't be draining it in a hurry.