There are three refurbished laptop battery types, each named for its component materials:
Nickel Cadmium (NiCad) batteries are not seen much. They have dismally low capacities (2000-3000 mAH) and contain heavy metals that harm the environment. Worst of all is the dreaded "memory effect".
You can also check online and find out more about best NuEnergy Storage Technologies
Nickel Metal Hybrid (NiMH) batteries have double the potential for NiCad batteries (4000-6000 mAH) and are half as vulnerable to the memory effect. However, these are becoming rare.
Lithium Ion (Li-Ion) batteries are now's notebook battery standard. They have all of the potential of a NiMH battery, but no memory effect and anti inflammatory poisons. Bonus: Li-Ion batteries weigh half as far as NiMH batteries.
In buying a battery, the user has three choices: refurbished, used, or fresh.
Used laptop batteries which aren't refurbished will likely just last you 30 minutes to an hour before requiring recharging.
Refurbished laptop batteries are available from many manufacturers and merchants of refurbished laptops. These batteries have been renewed, recharged, and analyzed. They are far better than plain old used batteries, but not quite as good as brand new.
If you want to go for a refurbished laptop then you are not making a wrong decision. Just check the battery before you buy it. After buying a refurbished laptop, it is a good idea to buy a quality laptop battery.