Here are some tips for choosing the best battery

The nickel cadmium battery, known as NiCad, is used as the most common type of laptop computer battery. However, by today's standards, nickel cadmium batteries can not hold much power and can only be charged for limited times. They can basically be damaged by being left in the charger after they have reached full charge, or by being recharged before they are dead. The latter issue, called the 'memory effect', means that in the event you recharge your universal laptop battery before it's run down, it would keep in mind that point at which you have charged the first few times, and only recharge that far and hold that charge from then on. Second, you need to know the model of your laptop computer. In the event you have no idea this or do not have the necessary paperwork, check the inside of your laptop computer battery's compartment while the laptop computer is off and unplugged, then you will find out the model number along with some other useful information. Also, you can find the P/N of your laptop computer battery on the battery itself.
The nickel metal hydride laptop computer battery, known as NiMH, is next only to NiCad. This type battery can hold considerably more power than NiCad, but they still have something of a memory effect.