The batteries in the InfoCrank cycling power meters are very common SR44 silver oxide cells. You may be able to find them at your local hardware store. They are also used for hearing aides and watches so places that repair watches may stock them. Ensure you buy the best quality batteries to get the longest use out of them.In development, we tested a large number of batteries and while most stated a huge lifetime (around 1000 hours according to our power drawing), even the best struggled to perform as specified (some lasted less than 200 hrs). Whatever you do, please buy the best quality batteries available for your InfoCrank.SR44 may also be labelled as 357 in the USA.Please make sure you purchase Silver Oxide batteries, NOT LR44 which are alkaline. Alkaline batteries will be drained in your InfoCrank within 2 – 5 days. If you have had short battery life, please check with your battery provider that you have purchased Silver Oxide SR44 or 357s.It is also now possible to buy good quality batteries online at very good prices. Once again, check for quality and only deal with someone who does a lot of business – i.e. moves their batteries quickly and does not carry old stock. Every country or continent has some good online battery shops and Verve also carries supplies of batteries. We can supply them to you, but they may cost more than some of the online dealers. Varta and Renata are brands we have usually found to be good quality.