Electricity+Voltage+testing

Testing for Voltage with a multimeter
Testing batteries is a super useful skill and is one of the best ways to practice with your multimeter The first battery we'll test is a new 1.5V alkaline. This one is a AAA but a AA, C or D cell will be the same voltage. Set the range to **2V DC**.  We read 1.588V, which you may think is a mistake, after all its a 1.5V battery so shouldn't it be 1.5V? Not quite, the 1.5V written on the side is just a **nominal voltage**, or the "average" you may expect from the battery.In reality, an alkaline battery starts out higher, and then slowly drifts down to 1.3V and then finally to 1.0V and even lower. [|Check out this graph from Duracell's page about alkaline battery voltage]  Using this graph you can easy tell how fresh your battery is and how long you can expect it to last. Next, we measure a 9V alkaline battery. If we still have the range set to 2VDC we will get a mysterious "**1.** " display, indicating is it over-range.  Fix the range so that it's 20V, and try again.  For this new battery we get 9.6V. Remember that battery voltage is //nominal//, which means that the "9V" is just the**average voltage** of the battery. In reality, it starts out as high as 9.5V and then drops down to 9 and then slowly drifts to 7V. [|You can check out the discharge curve in the Duracell 9V datasheet] If we want to check a rechargeable AA battery, and it's set to a 20VDC range, we will read 1.3V, which is about what a fully charged NiMH battery will measure.  If we fix the range so it's **2VDC**, we can get an extra digit of precision. This meter probably isnt more than 0.5% accurate so the precision may not mean much.  Finally, I test a lithium 3V coin cell, its at 2.7V which means it's getting near the end of it's life. <span style="background-color: #ffffff; font-family: Times,serif; font-size: 14px; text-align: left;">