How Batteries Work
Generally speaking, batteries are categorized into two classes:
- Primary batteries, the non-rechargeable battery that we’ll call standard.
- Secondary batteries, the rechargeable batteries.
What’s in a Battery?
Batteries contain one or more cells. Each cell consists of two different types of metal, the electrodes. The cathode is the positive (+) electrode of the battery and the anode gives off a negative (-) charge. On household batteries, such as flashlight batteries, the cathode is the end with the bump and the anode, the flat end. These ends are the battery terminals.
The electrodes are always separated – sometimes by space and sometimes by an inserted separator – and are immersed in a chemical, the electrolyte. The chemically based electrolyte reacts with the two different metals and determines which one is positively charged and which is negatively charged.
All Energy Seeks Balance
The meeting of positive and negative energy creates a balance. The ions on the cathode are fixed, but the negative ions (electrons) on the anode are free to move. However, the electrolyte keeps most of the electrons from passing through it. If it didn’t, the positive and negative charges would quickly be balanced and neutralized. So, if the electrons are to create a balance in the cell, they must move from the negative end of the battery and find a path back to the fixed ions on the positive end of the battery.
If you look inside a flashlight, you’ll see a wire or flat piece of metal that starts at the back end of it and extends to the flashlight bulb. This wire is the conductor that lets the electrons move along it. The conductor connects to a load, in this case, the flashlight bulb. The electrons continue through the wires contained within the load and finally complete the circuit, when they exit the bulb and finally reach the cathode.
This flow of electrons is what we call the current. When there’s a break in the conductor or the load, because they are unable to complete the circuit, the electrons stop in their tracks.
Dead Batteries
The shelf life of a standard battery depends on the composition of the electrolyte and the types of metals used in the battery’s construction. Although electrolytes impede the flow of electrons to the cathode, some do manage to wiggle through. Additionally, the electrolyte continually reacts with the metal components of the battery. Over time, this chemical reaction depletes the supply of new electrodes and the standard battery ‘dies’. The death of a battery occurs when the positive and negative charges are in balance. Unfortunately, it usually happens when you least expect it and most need your battery to work!
The electrolyte’s chemical reaction eventually uses up the batteries “juice”.
The reason why some batteries are rechargeable and some are non-rechargeable is easily explained by comparing the electrolytes to water. When you heat a pan of water, it turns to steam and once the pan runs dry, the water is gone - you can’t put it back in the pan. However, if you cool a pan of water, it turns to ice but, when heated again, you have a pan full of water.
The chemical reaction in a rechargeable battery generally isn’t strong enough to fry the battery. Yet, although the chemicals in a rechargeable battery don’t really freeze, rechargeables can “go cold”. A strong benefit of the rechargeable battery is that when it “freezes” it can be revived in a battery charger.