Motorola T5522 UK Nicd Black Twin Pack

I bought these radios for my staff at work. At first they worked like a dream but then the battery life began to dwindle somewhat (after 3 months) and most of them now run on 3 AA batteries. On buying these radios I was not warned that 'concrete structures' could affect the useage of the radios until I read the manual and unfortunately I happen to work within a 'concrete structure' As these radios are primarily for health and safety I am disappointed that at times, some refuse to work. Any occasion where staff have had to go outwith the building has also meant there is no communication.
Perhaps they are ideal for overall outside use but for the purpose of communicating between staff within a large building, they have failed to impress.
Regards L McKay