is it essential to charge for eight hoursnokia mobile while it purchase?

Rechargeable batteries and their management is complex...it is sensible to follow the manufacturers directions. If you do not you may well lose battery capacity or life.

I think what you're really asking is:

Is it essential to charge the battery for eight hours after being purchased?

I've received this advice from the store when I buy a battery. They say that you should charge the battery overnight (or for eight hours) and then follow the manual's recommendation for regular charging.

Personally, I don't know if this is valid. Doesn't say that this should be done so I don't do it. As soon as the charger indicates full charge, I take the battery off.

Overcharged batteries may either get so hot that they melt. Sometimes they blow up! Don't risk it.