Batteries in the Language Adventures series books

The Language Adventures series books contain 3 replaceable AG10 button cell batteries. These can easily be found at on-line retailers such as Amazon.com. These batteries are fairly inexpensive, on average $3 for a pack of 10 to $5.99 for a pack of 50. They are sometimes sold under different names such as LR1130, SR54, LR54 or others. Here's a helpful Wikipedia article. Shelf life of these batteries varies from 1 to 3 years. We recommend buying the long shelf life version.