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
After some extensive testing that I looked at from my work I went with PowerEx batteries for myself. They've got a 2700 mAh capacity, and they held up at high current (> 10A). They weren't the cheapest ($19/4 pcs)
It's also worth noting that NiMH batteries all have the same chemistry, and can be charged by a standard NiMH charger.
Just a little tip: Keep an eye out on Amazon deals for Sanyo rechargeable. I got a 48 pack for under $20 during a sale (with out charger).
They last ten times longer in my Digital Camera Compared to Disposables.
They are the best.
First the technology. Throw-away Alkalines have good capacity, reasonably good shelf life, and good voltage to start with but their voltage goes down a lot as they are used which is what causes flashlights to start going orange and dim after you use them a little while. NiMH and NiCad will usually maintain their voltage a little better until the end. LiIon is the best here but I don't think you can buy LiIon rechargeables in AA size. Also Alkalines don't work very well when cold, and their voltage will drop a lot under real heavy load. NiMh will maintain higher voltage and put out more current at the same time.
Different brands of NiMh have different capacity ratings, in milli-amp hour (mAH), and even at the same capacity they will vary in actual use just like these tests showed. NiCad is the worst for self-discharge, but NiMh is not too bad. They will work OK for devices that you use reasonably frequently but not for a flashlight that you put in the closet and use once a year. Alkalines will work better for this, but if you leave the device for several years then when you get ready to use it the batteries might have leaked and ruined the device. Use Lithium throwaways for this.
I haven't used the NiZn. I wonder what their voltage characteristics are under load.
NiCad and NiMh usually require different chargers but some chargers have a switch for this. I don't know if the NiMh and newer NiMh can use the same charger. Unfortunately the good battery chargers can be pretty expensive. Slow chargers tend to be the cheapest but a good fast charger can be a lot more convenient.
I have also heard of nutty people discharging them at more than 12C inside home-built portable aircraft landing lights with no damage where cheaper cells literally melted down.