Batteries--every parent's worst nightmare and one of the main occupants of your kitchen junk drawer. There are batteries lying around everywhere--small cylindrical batteries, thick rectangular batteries. You probably don't even know where they came from or for what they might be used.
For a quick lesson, it is good to know that AAA, AA, C and D batteries are all the same voltage--1.5 volts. What they differ on is amperage, which means that they contain different total amounts of energy (which is also why they are different sizes).
D batteries are typically used in high current drain applications, meaning in products that require an extended running time. Flashlights, radio receivers, megaphones and the once-popular boombox are all items that usually require D batteries. The use of D batteries allows these devices to be on for extended periods of time without the batteries dying and needing to be replaced quickly. That allows you more use of your products and to keep more money in your wallet.
There are both rechargeable and non-rechargeable D batteries. Rechargeable batteries allow you to be eco-friendlier, as you are not throwing batteries away constantly. It also allows you to save money. While the initial monetary outlay for rechargeable batteries is more significant than a regular pack, the charging cost is negligible--a few cents per charge. If you are replacing D batteries in a product often, you can save serious money by switching to rechargeable batteries.
Another way to become more eco-friendly in regards to all types of batteries, not just D batteries, is to buy a battery tester. Batteries are not drained equally when used in devices, though the majority of people think they are. So while you think that your remote control isn't working because both batteries need to be replaced, it could be the case that one battery still has life left in it. A battery tester will show you the voltage of each battery and how much "juice" is left in each. Finding out that only one battery needs to be replaced will save you money.
Batteries might cause a lot of clutter, but they are important items to have on hand. If you use them often, it might be worth investing in rechargeable batteries for meeting your needs.