Wondering if the batteries have improved/got cheaper/have more capacity since I got mine 4 years ago? Is tyhere anywhere you can buy them (more cheapy) than Cyclotricity?
You can use any battery you want with a Cyclotricity as long as it's the same voltage. In other words, there's no need to use the same type or quality. The battery is joined by two wires. Show us your bike if you want more specific advice.