• What is an NBN Battery?
  • Learn how long an NBN battery lasts
  • How to source replacement batteries

A reliable Internet connection is no longer a luxury but a necessity and the NBN has changed the experience, offering high-speed Internet access like never before. 

However, this connectivity is dependent on a crucial component often overlooked: the NBN battery. 

So, what do you need to know about NBN batteries? And where can you get a replacement?

What is an NBN battery? 

When transitioning to an NBN network for your home or business, you might consider equipping it with a Power Supply Unit (PSU) featuring a battery back-up. 

While this isn't a mandatory offering from your Internet service provider (ISP), under certain circumstances, it may provide and install a battery back-up for you. 

This back-up system can supply emergency power to your NBN connection box for up to 5 hours during a power outage, with some models extending that duration to 11 hours. 

How long does an NBN backup battery last? 

Well, it can technically provide power for up to five hours during a power outage. However, it automatically turns off when it reaches 40% battery life, which is typically after about 3.5 hours. 

You can extend this by pressing the 'emergency reserve' button, giving you an additional 1.5-ish hours after a few minutes. To further extend the backup time, you can connect an uninterruptible power supply with a 230V 50Hz AC waveform.

In terms of overall longevity, NBN Co estimates that the battery will retain around 70% of its full capacity after 3.5 years (equivalent to around 3.5 hours per full charge). If you hear beeping, it's time to replace the battery. Four beeps per minute indicate that the battery is at 50% overall capacity, providing around 2.5 hours per full charge.

To ensure optimal performance and longevity of your NBN backup battery, it's important to avoid exposing it to extreme temperatures. Temperatures below -1 degree Celsius can accelerate battery drainage, while temperatures above room temperature (around 20 degrees Celsius) can lead to faster aging. 

Additionally, frequent power cycling, or turning the battery on and off, can reduce its lifespan by up to 1.5 years from the estimated 70% capacity mark. Look out for audible alarms and regularly check the battery indicator for any issues. If your provider recommends replacement, it's crucial to follow the right advice to maintain uninterrupted service.

How to replace your NBN battery

To safely replace an NBN backup battery, it's important to follow these steps carefully. Before proceeding, review the NBN Co FTTP connection box guide (PDF) and consider seeking professional assistance if you're unsure:

  • Turn off and disconnect the Power Supply with Battery Backup from your home's mains electricity.
  • Open the cover of the Power Supply with Battery Backup to access the battery.
  • Disconnect the red positive plug ('+') from the NBN battery.
  • Locate the tabs above and below the NBN battery, then push them outward.
  • Lift out the NBN battery and disconnect the black negative plug ('-') from the NBN battery.

The NBN battery can now be fully removed and disposed of appropriately.

Where to buy replacement NBN batteries 

The Power Supply Unit uses a standard battery. Contact your ISP to inquire about replacement battery options, as it may provide them or you may need to purchase them yourself.

Replacement batteries are available from several stores in Australia, including Battery Works, Battery World Australia, Marshall Batteries, R&J Batteries, and Supercheap Auto. 

Guidance on installing the replacement battery can be found in the installation guide provided by NBN and in an online guide from NBN Co. Recharging the battery after replacement may take up to 24 hours.


As with any battery, the NBN backup battery degrades over time. While it can retain up to 70% of its charge for 3-5 years, frequent power cuts can accelerate this process. To prolong its lifespan, it's best to minimise switching your main power on and off. Similarly, avoid disconnecting the Power Supply Unit for extended periods to ensure optimal performance.

If you have further questions, feel free to contact our team at Compare Broadband on 1800 061 200 for immediate assistance.