@ankurjalgaonkar : i have my demat account with a cooperative bank and trading account with 2 different brokers one is a big brokerage house, Ltd company and the other is a very old Nse member proprietorship firm.
POA is not needed .
@ankurjalgaonkar : EITHER you have to give poa ,normally to a broker where you have trading account and the broker will do on your behalf OR you have to do it yourself through Speed e ( nsdl ) or Easi ( cdsl) or dis slip .