Battery Types

NiCd cells were the forerunners of the cells we use today. Many power tools still use these cells. NiCd cells suffer from the disadvantage that if not fully discharged and are charged they pretend to be charged and then run flat very quickly. This effect is know as the "memory effect"

Generally they are good for 200 recharge cycles.

Cell Voltage is 1.2V

Nickel Metal Hydride or NiMh

These cells have become the replacement for NiCad cells and will be offered in preference where the size required is available. They offer a higher storage capacity and therefore will produce more torque and will last longer between charges. These cells do not suffer from memory effect and can be recharged fully from any state of discharge.

Standard NiCad chargers can be used with these batteries.

Generally they are good for 500 recharge cycles.

Cell voltage is 1.2V

Lithium Ion or Li-ion

These cells are the next generation of rechargeable batteries. They deliver power at higher voltages i.e 3.6V and extensive use has been made of these cells in portable computers.  Management circuitry (Protection Circuits) are employed in the battery packs to prevent overcharging and explosion.

Cell Voltage 3.6V

Battery Sizes (NiCd or Nimh)

The table below provides battery cell dimensions to assist you in
determining the cell size to meet your requirements.

Power and Voltage

Battery power is measured in mAh. For example an AA cell rated at 2300mAh will sustain that power draw for one hour. If two such cells are placed in parallel i.e. the positives are joined together and the negatives are joined together the combined voltage will be 1.2V but the storage capacity will be 2*2300mAh or 4600mAh. To double the voltage and keep the power the same then connect the two cells in series i.e. positive to negative.

Take care when working with these cells - accidental dead shorts will produce some spectacular arcing and melting of tools. Remember they are high power!