What are cordless power tool batteries and chargers made of?

28th February 2020


	What are cordless power tool batteries and chargers made of?


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			Cordless power tool batteries and chargers are complex and contain a lot of different materials, particularly in their circuit boards and cells. Below are the main materials used to make the devices.

			Casing materials
			Plastics Thermoplastics (plastics that can be reshaped when hot) are heated and moulded to make the casings of batteries and chargers. These plastics are mostly hard plastics but some have a softer feel.

			Plastic foam is used to pad the cells inside the battery casing, absorbing any shocks the casing might get during use.

			Rubber Rubber is used in small amounts as rubber feet on the base of some chargers to prevent them slipping on a table during use.

			Contact materials
			Contacts need to be made from a highly conductive metal to allow the electricity to pass through them and complete the circuit.

			Brass Brass is an alloy (mixture) of copper and zinc. Changing the amounts of each or adding other metals, such as aluminium or lead, changes the properties of the brass. It can be made so it is highly electrically conductive.

			Brass is softer than other metals and so is less likely to spark when the contacts touch each other. Sparking caused by electricity can be dangerous if there are flammable materials around such as dust or gas. Brass can also have a high level of corrosion resistance – a useful property for contacts as they have a high risk of corrosion.

			Spring brass Spring brass contains 30% zinc. It’s conductivity is not as efficient but it is the cheapest contact material.

			Stainless steel Stainless steel has excellent electrical conductivity and is corrosion resistant, perfect for battery contacts. Although expensive if the contacts need to be stamped into shape, it is suitable for battery and charger contacts.

			Beryllium copper This alloy contains about 92% copper and 2% beryllium and is one of the best materials to make contacts with. It is very durable and has excellent electrical conductivity properties. On the other hand it is relatively expensive.

			Plating of contacts
			Contacts are sometimes plated with another conductive metal to make the contacts more corrosion resistant or to increase their conductivity.

			Gold Gold plating ensures that the contacts remain connected even under harsh environmental conditions.



			Nickel Nickel plating increases the conductivity of stainless steel by preventing films from forming on the steel’s surface. The films can reduce the stainless steel’s normal electrical conductivity.

			Circuit board
			Copper A copper sheet is laminated with a non-conductive material and the electrical circuit is etched and soldered onto the sheet. Copper is ideal as the main component of the circuit because, of all the metals, it has the highest conductivity. It is also very durable and can withstand high temperatures.

			Thermoset plastics Thermoset plastics, sometimes reinforced with glass (fibreglass) are used to laminate and support the copper sheet. Thermoset plastic, once heated and shaped, cannot be heated and shaped again, making them very resistant to damage from heat produced by the electrical circuit.

			Cell materials
			Nickel Nickel oxyhydroxide is a chemical compound used as a positive electrode (the cathode) in both NiCd and NiMH batteries.

			Cadmium Cadmium is a toxic metal that is used as the negative electrode (the anode) in NiCd batteries. NiMH batteries use a less toxic metal alloy instead.

			Lithium Lithium is a very lightweight metal that easily forms into ions in Li-ion batteries. Ions are essential for the battery to work (see How does a cordless power tool battery work?)