Well when you get beyond AAA batteries (I think the Chinese and Japanese systems are a little simple D is type 1, C is type2,.. You enter the world of strange numbers and letters. Here’s decoder ring for just one type R44. As an aside, the code is the type of battery is the first letter, then R means round and 44 is an 11mm diameter x 5.2mm high cell
- LR44. LR means alkaline and these generally are the least desirable. Relatively short battery life.
- SR44. These mean Silver Oxide and are longer lived. Getting a brand name also matters quite a bit
- 303/357. If that isn’t enough there are not standard names for these small watch batteries, so an Everyday 357 is the same as an SR44!@#$
These only come in these flavors, but the flat batteries also come in the CR type which means lithium. 10 year life. And if that isn’t enough a CR2016 is not the same as a CR1620