After five years and many cycles, the 12-volt NiCad battery pack on my portable drill/driver expired. I learnt that replacing it through the agents would cost me R395, so instead, I devised a way to give it a new lease on life.
Disconnect the battery pack and solder extension wires to the outside. (Keep the redundant batteries inside for the sake of balance.) Connect the two leads to a 12-volt rechargeable sealed battery (of the type used in alarm systems and electric gate controllers) in a plywood cradle.
The new pack must be recharged using a stronger charger than the one that came with the drill (I use my car battery charger). The result – superior battery endurance at a cost of about R150. Portability is only slightly hampered.