Ok a few quick notes, we have a Steripen thing that cleans up water with a UV light. Needs CR123 batteries, wandered over to Bartells and they are $16 a piece there (what!). A quick search of the internet reveals widely varying prices from$7  on Amazon to $2 at Thomasdistributing.com. I'm going to try the$2.25 Panasonics. Also looked at rechargeables but at $23 for two plus a special charger, it would take a long time to go through the conventionals. Then we have a bike computer that uses a Maxell LR44 whatever that is. There is an entire web site devoted to the topicTurns out it is an alkaline battery that is 20% of the price with 150mAh vs 175-200mAH for the SR44. A little more study says the SR44 or 357 (which has lower internal resistance) by Energizer using silver oxide has a long constant voltage before dying, so on to them. Their big drawback is that a LR44 can last up to 10 years so it is good for things that don't get much use whereas the SR44 is good for sensitive instruments (cameras) that like a constant voltage. So LR44s for me 🙂 Shop4Tech offers and incredible 10 batteries for$5 and 4 CR-123s for \$8! So I'm giving them a try. Wish me luck!