Two items work only 30sec then switch off.

The battery pack is a 5 cell unit plus circuitry. The circuit monitors the cells during charge and discharge cycles. If one or more cells drop below a threshold safety voltage on discharge the circuit will shut down. The cause of the rapid drop in any one cell is due to ageing which is an increase in internal resistance and an inability to hold charge - a loss in capacity. If any one cell has aged all cells need replacing. They are LG HB7 units which need contact welds and soldering.