The Declaration of Independence tells us that, “all men are created equal.” Yes, they are. Batteries aren’t, however. When you are shopping for a flashlight for the cockpit, or batteries for your electronic flight computer, you’ll need to consider what kind of batteries will be required. Some flashlights can use rechargeable batteries. Others can’t. Some devices (like ultra bright mini-flashlights) require fairly expensive batteries with limited operation time like the CR123A. Fortunately, there are some very good rechargeable batteries that can be used in a number of devices pilots use. Rechargeables save money, natural resources, an minimize e-waste. Always check with the flashlight or calculator manufacturer first to see what they recommend. Instead of re-inventing the wheel, here’s a series of articles on rechargeable and non-rechargeable batteries you’ll find informative: Nickel Cadmium (NiCd), Nickel Metal Hydride, Lituium Ion, Alkaline, and Rechargeable Alkaline. They all have pros and cons. No, I guess you can’t really say they have pros and cons. It’s just a matter of which kind of battery suits your needs. For instance, Lithium Ion batteries have a shelf life that can extend as long as 10 years! But, once removed from their chargers, most rechargeable batteries start to self-discharge within a week. The Lithium Ion battery is great for flashlights that are only used occasionally over a long period of time. Rechargeables are better for items that are used a lot and would otherwise require the frequent purchase of new batteries.