Battery Technologies

Battery Technologies

Disposable batteries are commonplace in portable electronic equipment, generally low cost and reasonable power delivery, and not having to be tied to a mains supply, it seems we’ve been addicted to them in past decades, but is our addiction starting to wear off with the advent of new rechargeable battery technologies? We're covering the basics of different battery technologies here as the terminology often comes up in everyday life, and can be confusing.

 

Disposable Batteries (dry cell):

Zinc-Carbon Batteries

These batteries create voltage through a chemical reaction between the zinc casing forming the negative through an acidic ammonium chloride electrolyte to a manganese dioxide mixture surrounding a carbon rod in the centre forming the positive.

They were the first commercial disposable battery type to be invented, and are still produced by some manufacturers.

Zinc Carbon batteries are around 1.5V per cell, with the voltage dropping as the battery power runs out.

[Image showing cutaway of a typical zinc-carbon battery]

Alkaline Batteries

The most common disposable batteries, with more a higher capacity and longer shelf life than zinc-carbon batteries.

Similar to Zinc-Carbon batteries, zinc and manganese oxide are used, but steel makes up the casing instead of zinc, and an alkaline electrolyte of potassium hydroxide is used instead.

Alkaline batteries suffer from potential leaking as hydrogen produced increases internal pressure creating a rupture, expelling potassium hydroxide.

Alkaline batteries are around 1.5V per cell, with the voltage dropping as the battery power runs out.

Lithium Ion batteries

The composition of these batteries discussed further with their rechargeable counterparts.

Available as single use cylinder batteries as a direct replacement for Alkaline and Zinc-Carbon batteries, where long life and significantly higher power requirements are necessary. Smoke alarm that require function over several years is a typical application of long-term use, whereas a camera flash shows the extended power application ideal for professional photographers who don’t want to keep replacing batteries during a photoshoot.

The costs of these batteries are also significantly higher, so their market-share is limited to specialist or commercial applications.

Voltage is around 1.5V per cell, with the voltage dropping as the battery power runs out.

 

Rechargable batteries (Dry cell):

Nickel Cadmium (Ni-Cd) Batteries

“Nicad” Batteries were once the most popular rechargeable batteries on the market, as direct replacements for their disposable counterparts, as well as in rechargeable battery packs for camcorders and power tools.

Power is created by a chemical reaction between nickel (Ni) hydroxide and cadmium (Cd) with Potassium hydroxide as the electrolyte.

Their voltage is typically around 1.2V, dropping off only when the battery has almost fully discharged.

Nickel Metal Hydride (Ni-MH) Batteries

These batteries superseded Nickel Cadmium batteries thanks to a greater capacity and have subsequently taken a large part of the market share from Nickel Cadmium batteries.

They work much the same way as Ni-Cd batteries, but use Hydrogen instead of Cadmium in the chemical process.

Their voltage is typically around 1.2V, dropping off only when the battery has almost fully discharged.

Lithium Ion (Li-ion)

Lithium Ion batteries are leading the way with rechargeable batteries, they’re lightweight and pack a lot of available power for their size. Various types of Lithium battery chemistry exist with various advantages, such as longer life and safety. We’ll focus on Lithium Ion batteries, being the most common type used in portable handheld devices.

Lithium ions in the negative electrode are drawn to the positive electrode through an electrolyte. Charging reverses the process with little memory effect that other battery technologies suffer from.

Rechargable lithium batteries are typically in multiples of 3.7V, as single or multiple battery packs.

The batteries either come in cylindrical form, such as the common 18650 battery (18mm diameter by 65mm length), or in a flatpack form.

We’ve recently come across a 1.5V lithium Ion battery as a rechargeable replacement for primary batteries, complete with 5V USB charger sockets. Internal circuitry clearly handles the voltage differences.

Because of the high energy density and composition of Lithium Ion batteries, they can catch fire and explode, something that has plagued manufacturers of certain consumer electronic devices such as ‘hoverboards’. Gassing (or swelling of the battery) is a sign that the battery needs to be replaced immediately.

Lead Acid

Lead Acid batteries are the oldest battery type, but because of their large size and significant weight are typically restricted to automotive and power generation / backup applications.

From starting cars and powering the electricals to providing a backup power supply for emergency lights and fire alarm systems, they are some of the most reliable batteries available, and have certainly stood the test of time.

Common lead acid batteries made from lead plates with a sulphuric acid electrolyte. When the battery discharges power as it is used, the lead reacts with the sulphur. A problem with some lead acid batteries is that the lead plates can become so badly sulphated because the voltage has dropped too low, that the chemical reaction cannot be fully reversed, so the battery won’t hold a charge anymore.

When charging the battery, hydrogen gas (along with oxygen from the water) is evolved. Hydrogen is explosive, so lead acid batteries should not be charged in enclosed unventilated areas. In time, as more hydrogen is produced, the water level may drop, so it is common to top of lead acid batteries with distilled water (not acid).

Sealed lead acid batteries are available, and these are typically used in enclosed areas, such as battery backup power in alarm systems. The electrolyte is formed from a gel, so the battery can be used on its side or even upside down.

Lead acid batteries are usually made up of several cells in series, a typical 12V lead acid battery would be made of six 2V cells. 6V batteries were common on old cars, 12V is still the standard on modern cars, and 24V is used on lorries and trucks. 6V and 12V lead acid batteries can be found in battery backup systems. Other voltages are available in specialist applications.

 

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