Originally posted by kamilyun
I'd like to hear your take on these. I've got a 1 year old daughter, tons of toys, and just invested in a cheap Radio Shack rechargable system. Bought a mix of AA's, D's and C's.
Hope it was worth it! 
Regular Alkaline batteries are rated at 1.5 volts. When they're brand new the voltage is around 1.6. When they're getting dead, 1.4 and below. If you looked at a graph of an alkaline battery being discharged at a constant rate, it almost like a linear curve, but not quite.
Rechargeable NiMH (I'm not going to cover NiCd because you really don't find them anymore in the AA, C, D etc consumer form) are rated ar 1.2-1.25 volts. When they are full charged, they're generally above 1.4 volts. When they're dead, they are about 1.0 volts. Now, NiMh discharge graph looks a little different.
The ,2C, 1C, 3C are just discharge rates, higher the number the more electricity being drawn from it. As you can see, the NiMh spends most of is life operating around 1.2 volts.
What's good about NiMh batteries:+ You can recharge them anyways from 500-1000 times.
+ The batteries generally do not have to be drained all the way dead before you recharge them.**
+ The work excellent in
high drain devices. Often 2-3 times longer than alkaline.
+
Drawbacks of NiMh+ They lose their charge quickly. If you charge a set of batteries up, after a month of not being used, you'll need to recharge them again. Rayovac Hybrid batteries are a little better, they can hold the charge from 4-6 months, but at a cost of capacity. I believe they are 2100mah. Most new AA size rechargeable are 2500-2700. Some I've seen at 2900, I'm sketchy about those, a lot of companies like to 'fudge' their numbers a bit. At work we have a Cadex machine that can actually test the capacity of batteries and I've seen some off brands that test below what they claim to rate themselves at.
+ Do not operate well in low drain devices. In something say like a TV remote, Alkaline batteries can last for years, NiMh do no operate well in low drain devices. You'll be recharging those batteries every couple months in a TV remote.
+ They operate at a lower voltage. This is generally the biggest kicker. Unless the device is specifically designed to operate with rechargeable, it may seem that you're rechargeable are 'crappy and are dead quickly. Well think of it this way. Let's say the toy takes 4 AA batteries. AA alkaline batteries would produce 6.0+ volts. The device will work well. 4 NiMh when fully charge may be 5.5 volts or so when fully charge. May work okay for 10 minutes, but as the graph above shows they operate at 1.2volts most of the time. So thats really 4.8 volts. The device may act if its dead or dying all the time, thus a lot of people try and recharge their batteries again after 10 minutes and complain a lot. (I hear this a lot from customers)
So quick recap, NiMh work great in devices that chew through batteries like handheld games, cameras, etc. In a simple light up toy? Use an alkaline. Remember, the device really has to be designed to use Rechargeable batteries to operate fairly well. You may have to do try and error to see how it operates as users manuals (other than high tech toys) will not say a blip about it.
If the device is NOT designed for Rechargeables, the best of the best you can try is Energizer Lithium batteries. But they're $10-12 a four pack. And honestly not worth it in standard toys. If you have a digital camera and use it 3 times a year, dont buy rechargeables, buy lithiums please.
Now the difference between brands is so small these days, stick with whats on sale. Duracell is usually the most expensive. You can find great steals on Rayovac. The big 3 companies still produce their batteries in the USA. Other brands like Panasonic or something else, do not.
Good rule of thumb for pricing a good deal on batteries. AA steals are about 20 - 30 cents a battery. Divide the # of batteries in a pack by the price. What I can get with my discount is about 13-14 cents a battery.
And a last note, Heavy Duty batteries are not Heavy Duty. They are an older chemistry and last 1/3 as long as alkaline. So if you're in the checkout and see oh boy 4 pack for 99 cents? If they're Heavy Duties, do not buy them. Unless you plan on replacing the batteries in your TV remote.
