To see how these rechargeable batteries compared to each other, I charged them according to each manufacturer’s instructions and then ran them down in two ways to simulate how batteries are used:
· Using a Husky flashlight with a 2.4-volt Krypton bulb and a pair of AA batteries, I turned it on at the same time I started a stopwatch. When the light went out, I stopped the watch. The flashlight constantly drains the batteries until the cell’s output drops below about 1.2 volts.
· Using a CD player that is powered by a pair of AA batteries I listened to a CD set to shuffle among its tracks with a stop watch running. To monitor the power drain, I connected a voltmeter to the battery terminals. Unlike the flashlight’s constant drain, the CD player uses power intermittently. The player’s motor is its biggest power drain and cycles on and off as needed.
I also measured how long it takes to recharge these cells by running a stopwatch while they were in the charger and measured how hot they were with an ExTech IR201 Pocket IR temperature gauge. At the same time I used a Kill-A-Watt power meter to monitor how much electricity the charger was drawing.
This let me estimate how much power the charger would use over a year of weekly charging of two AA cells. I used the Department of Energy’s national average of 11.6 cents per kilowatt hour of energy in the estimate.
|Energizer Rechargeable||PowerGenix NiZn||Rayovac Hybrid Rechargeable||Sanyo Eneloop||Duracell disposable|
|Initial charged voltage||1.46 volts||1.79 volts||1.46 volts||1.41 voltage||1.61 volts|
|CD player run time||4:32||14:05||9:21||13:35||12:30|
|Flashlight run time||1:53||DNF||3:41||4:05||5:03|
|Temperature of cells F||100 degrees||80 degrees F||97 degrees F||87 degrees F||NA|
|Notes:||DNF: Did not finish: bulb burned out after 10 minutes|
NA: Not applicable for disposable batteries
*: Charge times are for desktop and 15-minute charger