Batteries are a complex thing. So if you want to squeeze out every bit of performance from a flashlight you need to understand a bit more about these magical, portable power cells. Most of us know batteries by their conventional names: AAA, AA, D, and C cell. But there is another range you should know, including CR2, CR123a, 18650, and 26650 battery.
If you plan on having a few lights for regular and emergency use then you can’t take chances. In that case, you should get a little light that can run on any kind of cell, one headlamp that runs on primaries, a lantern that runs on primaries, and a big light that runs on rechargeable batteries.
So, how do choose a flashlight battery?
Volts & Milliamps
There are two numbers linked with batteries: volts and milliamps per hour, or V and maH, respectively. A volt, in layman’s language, is a measure of a battery’s bandwidth, basically how much power it can discharge at a time. While maH is a measure of the total amount of energy stored in a cell.
For a flashlight, you want high discharge rates and lots of maH. These things aren’t easy to find on common cell boxes, but impossible as most Rechargeable batteries are getting those high numbers.
Primary & Rechargeable Batteries
Over time, if you want to see what the latest lighting tech can do you will migrate to having a variety of cells: primaries (non-rechargeable) and rechargeable.
Rechargeable works better in two scenarios: ultrahigh performance lights and regular carry/use lights. Because these lights get used regularly, you can simply charge up the batteries and save money. Rechargeable also has better specs, allowing lights to have much higher lumen counts and longer runtimes.
Some rechargeable cells, lithium’s mostly, can cause fires/explosions when overcharged, but in years of using them, this has never happened to me
There are four main chemistries ie, alkaline and lithium for primary cells, and NiMH and Li-ion for rechargeable. Most lights run on the first three, but the higher voltage on Li-ion batteries can tax circuits and emitters, making them the least common chemistry used. There are some emerging chemistries out there, like lithium-polymer rechargeable, and even fewer lights can use those.
Emitter tech is at the point where you can get by in 99% of circumstances with a single cell AAA or AA light. For regular carry that is what you would prefer to use. If you want good NiHMs look no further than Eneloops. They are the most complete system and best-reviewed rechargeable on the market. For li-ions I like Ultra fire, though here label swaps make it hard to follow manufacturers over brands. You can buy good on banggood at a pocket-friendly price. And being the global leading online store, you can expect high-quality products.