Are the batteries the same??

From:  "Robert"

Are all double a batteries the same?  do all batteries last the same amount of time?

Edwin did a bunch of homework for us and came up with this: 

batteries of any one type will generally be the same regardless of the company that made them (of course this is generally true for many products). The batteries will differ if they are of a different kind, for example a AA NiMH battery versus a AA alkaline battery. How long a battery lasts depends on a) how much current (measured in milliamps) you draw from it and b) the amount of charge (measured in milliamp-hours) it has. A milliamp-hour is the amount of charge that is removed after drawing 1 milliamp of current for 1 hour.----So, for example, if a battery has 500 milliamp-hours, you could draw a current of 20 milliamps for 25 hours, or a current of .5 amps for one hour, or one amp for half an hour. Of course, there is a limit to how much of a current a battery will about at any one time (for example, my experience has shown me that 9-volt batteries never output more than 7 amps).

TB helped out as always with this: 

There are 3 basic types of AA batteries:
GENERAL PURPOSE - cheaper batteries, do not last very long. ALKALINE - higher capacity, used for longer life at low loads. Recommended by most manufacturers. Not as good for high load use. RECHARGEABLE - Reusable batteries. negative aspects are cost for charger and batteries. there are of course other types but most stores do not sell them. If you are comparing all alkaline for example then most have similar characteristics. Info on batteries and FAQ on batteries

amr shalakani believed this: 

No 2 batteries are the same...it all depends upon their constituent ingredients...which are multiple chemical substances basically. But the most important is water....the lesser the moisture inside a batter the lesser it lives. that's why batteries live longer if we keep them in a refrigerator.

David K summed it up with this: 

No, not exactly. They all supply approximately the same amount of voltage and current, but the materials the battery is made of can significantly affect the battery's life. And of course, there are NiCad, Carbon, Alkaline, etc.