2. Not all batteries are the same, or even "good" to use for photography.
Let's break this down for you... there are several options out there... but typically only one or two that are able to be used for each camera.
So first, lets just all get on the same page and promise never ever to put regular Alkaline AA batteries in your camera. It doesn't matter if the manual says they "can work" Let's just all agree its a bad idea and here is why.
They don't have a lot of power causing your camera to be slow and for you to miss shots, or your focus to be slow.
Alkaline batteries leak. Every run into this? Leaky batteries + Digital camera = BAD as in buying a new camera in many cases.
They don't last very long. With cameras that run digital displays constantly its drawing a LOT of power and they simply don't have it to give so even as a back up option.... they suck and you would need a back up for your back up... and really at that point you could have bought a better option to start with.
If you do have a camera that uses an AA size battery here are some GOOD options for you.
1. RECHARGEABLE AA: (nickel–metal hydride battery, abbreviated NiMH or Ni-MH) These are my recommendation. Just spend the money and pick up a good charger (something that can recharge 4 batteries in say an hour or so) and an extra pack or two of rechargeable batteries. I always recommend a set for the camera, a spare for the bag and one that could be recharging. So 3 sets. Even in the highest shooting day this typically will have you covered! Your not going to go through 2 sets of batteries in an hour unless something is WRONG!
Besides, Rechargeable AA are great to have on hand especially if you have kids! Nice long life and quick recharge is a bonus!
2. The Lithium Ion or Li-ion AA The only time I would recommend this is if you were going to be somewhere that recharging isn't going to be an option. They are expensive and you can typically purchase a charger (or an adapter for your charger for a different country) easier and for about the same cost as stocking up on these bad boys. They are basically a high quality AA single use battery. Sure they say they last "9" times longer... but thats 9 times from regular alkaline AA's not from rechargeable AA. So, if your in a pinch I really would just suggest extra packs of rechargeable... so you can use them over and over again.
If you have the AA option don't get bogged down in the tech numbers like getting the highest mAh... it comes down to the better type of battery and which is more likely to deliver closer to its rated capacity for the camera... so NiMH beats an alkaline every time and the numbers aren't going to mean anything. If you want to read more ALLBattiers.com had a good Q and A about it... but its nothing to get to involved in unless your just a tech maniac
A nice tip also that I found for you over 15 BILLION ordinary batteries are thrown away globally every year. So rechargeable batteries can significantly reduce that waste! Plus you always what to make sure you are recycling all your batteries and disposing of them CORRECTLY!
However, most camera manufacturers at this point tend not to even offer cameras with the AA option. Mostly because they are slower, heavier, and more bulky. You can't have a slim camera if you have to find room for 2-4 big round batteries, ya know? So, as with most of technology you start getting into batteries that are custom made for that camera (or series of camera's) that way they can control the shape... and yes the cost.
For the most part your locked in to whatever battery the manufacturer creates for your camera. These are usually some sort of Lithium Ion... like what you would have in your cell phone. Small, lightweight and designed by the camera manufacture making them all different and you should have at least 1 spare (though again, I recommend 3)
These Lithium Ions do tend to have last much longer since they are designed FOR that camera. Just be very careful when purchasing additions or chargers for them. When in doubt take your battery with you and read the packaging carefully. A sony M type is much different then a Cannon for instance... and wont mix and match!
You can pick up good quality off brands for most... typically less expensive. I personally have never had a problem or noticed a difference in time. But there are bad ones in every bundle so to speak so keep in mind the old "if it seems too good to be true" and "you get what you pay for" sayings in mind when spending your money!
Hopefully this helps clarify a few things for you... now I feel this would be a very good time to tell you that I am NOT an expert in environmental issues, but I do feel strongly about learning what I can and passing along information so that you can make the correct decisions in your life and for your lifestyle.
Batteries in general are considered bad for the environment and should not be tossed away in general trash. Almost every photo lab I have been to has a way to recycle them, and now your cell phone batteries as well. This also means that other places like some cellular stores and other electronic retailers are also offering recycling for at least the popular lithium-ions.Many times its a simple bin you can toss them into around the front door or customer service area. I would encourage you when it comes time to pitch bad ones, or when your purging things that no longer have working devices to go with them that you look into donating for them to be re-used, or recycled.
If you are looking to get more information about eco-friendly companies or battery options Eco 20-20.com has several articles to help you out!