The firm had previously called back about 500,000 units because they posed a safety risk. At least one person suffered burns after a device exploded.
The extension covers about a further million copies of the kit.
"We are taking this action because we are aware of a very small number of further incidents where Power Bars have overheated," EE said.
The firm began offering the devices to its customers in April. Users were able to exchange depleted ones for fully-charged units in its shops, but could also recharge them via a USB connection.
Although consumers did not have to pay for the Power Bars, the firm is offering a £20 voucher to those who return the devices.
"Keeping our customers safe is extremely important to us, and that's why we're taking this voluntary and precautionary action," EE added.
Courtesy to BBC News