Good day @sino83,
Welcome to TPG Community!
The alarm means that your Backup Battery may be faulty or worn out. If this is the case, your TPG NBN Home Phone service will not operate when there is a power failure which means you will not be able receive and make calls including calls to emergency services.
Since your back up battery is still in warranty, to process the battery warranty claim, you must first purchase a new battery to replace your existing Backup Battery. Please note that the cost covered will be up to $30.00.
You can find information about the battery type and where to purchase it here:
To replace your Backup Battery, please follow the instruction here:
Where to buy a new battery and recycle your old one
Many specialist battery retailers stock a compatible battery for the nbn™ Power Supply Unit with Battery Backup Service. Some local councils also accept worn out batteries for recycling.
Some battery suppliers may also visit your home and fit the new battery for a small fee. These retailers are denoted in the "in-home battery replacement" column. Their fees vary and are not set by nbn, so ask the retailer for more details.
Battery World Australia - 13 17 60 - Available in-store - In-home battery replacement - Recycling of old battery*
Marshall Batteries - 1300 627 742 - Available online and in-store - In-home battery replacement - Recycling of old battery*
R&J Batteries - 1300 769 282 - Available in-store - Recycling of old battery*
Century Yuasa Batteries - 13 22 87
You may then send the receipt and serial number of the defective NBN battery to firstname.lastname@example.org to have this assessed as typical assessment time from NBN Co. is more than four weeks .
Let us know if we could be of further help.