Unable to Charge synergy 5500 phone?

The phone will not charge the new batteries they are Infapower, 1.2volt, 550mAh . Its fine at recharging on its current old batteries, but when you take a call, the phone cuts out. I have tried normal batteries to prove the phone is not faulty and screen come on as normal.Even when i have used a fullly charged set of batteries of the make from a working phone it still will not work. any ideas what the problem is?