Speaker at 100% but can only use when plugged in.

Hi @lornagrbin ,

If the speaker is no longer covered by the manufacturer’s warranty I suggest that you open the speaker and disconnect the battery and using a Voltmeter check if it is OK.

It may that it can no longer handle the load when required. Even rechargeable batteries have a lifespan

Here’s a link to the ifixit Logitech UE MegaBoom Battery Replacement guide which may help.

ifixit sells batteries for the speaker (restrictions apply). Here’s a link

Logitech UE MegaBoom Battery

Alternatively replacement batteries are available online. Just search for Logitech UE Megaboom battery to get results for suppliers.