what-are-cordless-power-tool-batteries-and-chargers-made-of

What are cordless power tool batteries and chargers made of?

Shop for Batteries and Chargers

Inside a battery are lots of materials particularly in the circuit boards of batteries and chargers and in the cells. 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

Thermoplastic can be melted and shaped to make the casings of the battery and chargers of cordless power tools.

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.

Foam is used to pad the inside of the battery casing to prevent knocks and shocks to cells. Plastic foam is used to pad the cells inside the battery casing, absorbing any shocks the casing might get during use.
Rubber is used for grips to stop the cordless tool batteries and chargers slipping from hands or tables.

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 of batteries and chargers of cordless power tools can be made form a number of different metals, some better than others. Contacts need to be made from a highly conductive metal to allow the electricity to pass through them and complete the circuit.
Brass is a very good conductor and makes a good middle of the road battery and charger contacts.

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.

Spark causes by electrical contacts of a battery and charger of a cordless power tool coming too close. 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 is the cheapest form of brass to use to make contacts from.

Spring brass

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

Stainless steel has excellent conductive properties for the battery and charger contacts of cordless power tools.

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.

Copper in beryllium copper is 92% of the alloy when it is used to make contacts for batteries and chargers for cordless power tools.

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

Plating of contact materials can make them more useful. Contacts are sometimes plated with another conductive metal to make the contacts more corrosion resistant or to increase their conductivity.
Gold is good for battery contacts because it creates a tight bond between them.

Gold

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

Wonkee Donkee says: What’s the use of golden carats? My carrot tastes much better!
Nickel is a metal used to plate battery contacts to make them more electrically conductive.

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 circuit etched into coppwer sheet for a battery and charger.

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.

Circuit board suspended in insulative plastic.

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 is a metal used to make nickel oxyhydroxide for battery electrodes.

Nickel

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

Cadmium is a toxic metal that is used to make electrodes of nickel cadmium 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 is a very lightweight metal so lithium ion batteries are very light.

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?)