SR416, SR416SW, SR416S, 337, LR416 Battery Equivalents and Replacements
SR416SW is very small button cell battery, commonly used in wrist watches, but also in calculators, credit card size devices, as CMOS battery etc.
Common labels of these batteries include SR416, SR416SW, SR416S, 337, LR416 and few more, but most reputable brands commonly use 'SR416SW', often combined with '337' label.
SR416, SR416SW, SR416S, 337, LR416 Battery Features and Specifications
SR416SW/337 battery is a really small battery, featuring diameter of 4.8 mm and height of 1.6 mm (~0.189 x 0.063 inches) and working directly with these batteries can be troublesome, especially for larger guys (been there, done that).
Best working tool for these batteries are of course, fingers with gloves (to prevent short-circuiting of these batteries) and special plastic tweezers.
SR416SW/337 batteries can be found commonly as silver-oxide batteries which are labeled SR416, SR416SW, SR416S, or 337.
Alkaline 4.8x1.6 mm batteries are rare and if found, they are labeled as LR416 batteries. Their nominal voltage is 1.5 volts, but it quickly drops over time, which is not desirable when used in electronic devices.
Since these batteries are used for watches and other sensitive electronics, practically all brands manufacture silver-oxide 4.8x1.6 mm batteries (labeled as SR416, SR416SW, SR416S, 337) and such batteries should be obvious choice.
Silver-oxide SR416SW/337 batteries feature capacity around 8 mAh - this doesn't sound much (and it isn't!), but it is enough for CMOS based and other similar units.
Silver-oxide SR416SW/337 batteries nominal voltage is 1.55 volts and is fairly stable during operation, with the cutoff voltage around 1.2 volts.
Note: actual cutoff voltage depends on the device being powered, but most units being powered with silver-oxide batteries support their use down to 1.2 volts per cell. Also, these are NOT rechargeable batteries - when they are 'dead', replace them with new batteries and dispose them properly (they must be properly recycled).
Silver-oxide SR416SW/337 Safety Concerns
Since SR416SW/337 batteries are so small, keep them away from kids and pets. If they accidentally get swallowed, contact the doctor/vet and act according to their instructions.
These batteries don't contain mercury (if they do, don't buy them), but when swallowed, fluids in human body close the circuit causing various chemicals reactions to start. Although it is not the same to swallow 8mAh and 50mAh battery, if something like that happen, contact emergency services immediately.
Long Story Short: SR416, SR416SW, SR416S, or 337 batteries are not so common batteries, but they can be easily found at online shops and thanks to fast delivery, they can be 'at home' rather quickly.
Considering their size, they are not the cheapest button cell batteries on the market, so if you need these, go for reputable sellers with 2 or more batteries per pack.
Again, although they are mercury/cadmium free, keep them away from kids and pets - they are really, really small batteries ...