If it's the round one, Fedog and Sowunto bike horn is the same as Juiced sold for about $50. About 6-8 mo. ago, there was a video on youtube that showed how to replace the battery but it looks like it has been removed (no idea why). The battery mentioned there is 7.4V 780mah battery. If I remember correctly, the housing of the horn unscrews for access. Fedog horns are sold on Aliexpress. In Feb, I bought one there for $30, listed as Fedog Electric Bicycle Scooter horn. You might be able to find the batteries there too. Opening it up to have a look can only help since the horn no longer works. Hope this helps. I keep mine charged regularly since they remain 'active' in some way and drain the battery. They will die if not kept up regularly.