charging light on then off?

My problem is that the battery charges to about 10% on an on a bit off a bit way until 10 % is reached. the charge only last about 5 - 10 mins. Blew in power terminal but nothing. Is the blue "I'm charging power light supposed to be on all the time or flash on and off. Is my answer a new battery? Any help grateful. Thanks.

alanr
May 2010