Batteries

May 9, 2004

Batteries are admittedly tangential to microwave engineering, but they are a component in almost every wireless gadget ever conceived. One purpose of this page is to educate the teeming masses on the difference between a battery and a cell, so you will get it right when you draw a schematic of that new doohickey onto a napkin. The material for this page was submitted by Tony, from the Electric Power Academy in College Station, Texas. Thanks, Dude!

A voltaic "cell" consists of one cathode and one anode. The cathode is the positive terminal, the anode is the negative terminal. A guy named Nate once said that you can remember this because "cats are always positive". Yes, he was disturbed, but now you too will remember...

A "battery" by definition is a multi-cell device (independent of the chemical technology and independent of it being primary or secondary). Thus common usage and the Energizer Bunny are often wrong: off-the-shelf dry cells labeled AAA, AA, C, and C are cells, not batteries. But if you buy the 9-volt product from the same rack in the grocery store, it is a battery because it contains several cells in a single case. Your car engine is also (likely) started by a real 12-volt battery. Here are the symbols for call and battery, note the difference.

Symbol for "cell"	Symbol for "battery"

Multiple cells are often arranged into a battery (e.g., there are two “D” cells in an average flashlight battery). Here is a symbol for multiple cells:

Multiple batteries are ganged in series in stuff like golf carts (six 6-volt batteries in series producing 36 volts) and in the old Morris Garage MG-B (two 6-volt batteries in series producing 12 volts, for better lateral weight distribution). Ganging in series provides voltage summation, with current generally limited to that of the weakest battery in the chain.

Batteries in series

Ganging batteries in parallel provides more current capacity due to lower source resistance. When you use jumper cables to start a car with a weak battery you are (hopefully) ganging the batteries in parallel (thanks, Howard!)

Batteries in parallel

Now you know! You will find these figures and many more in our downloadable word file called Electronic Symbols.doc on our download page .