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What is a battery back-up unit (BBU)?

Written by KCOM Support on 20/10/2022. Posted in Phone.

A battery back-up unit (BBU) may be provided by an engineer when we install your full fibre service.

  1. Maintaining your battery back-up unit
  2. What do the lights on the battery back-up unit mean?
  3. Additional support

If provided, it will ensure that your KCOM phone service will continue to work for a limited period (up to twenty-four hours of which one hour is talk time) in the case of a power outage. This will enable you to make and receive calls from the emergency services. It also allows you to make and receive important calls from a carer or a doctor as well as a family member, a friend or a neighbour. During a power outage, we would recommend limiting the use of your telephone to all but essential calls.

You must keep the battery back-up unit plugged into a mains power socket and turned on to ensure it is fully charged and so could work in the case of a power outage. It's important to know that, even with a battery back-up unit, in the event of a power outage you'll need a phone that works without mains power (e.g. a corded phone).

Maintaining your battery back-up unit is essential. It should be serviced once a year.

You are responsible for making sure the batteries are charged and for replacing them when necessary. For instructions on how to change the batteries, click here.

If we have provided the BBU because we have identified you as needing additional support that increases your dependency on the phone or because you don't have an alternative method of contacting the emergency services, we will maintain the back-up unit for you. This is to ensure that customers who require protection the most receive this and are not left at risk in the event of a power cut.

If you need this additional support, we'll contact you every 12 months to arrange for an engineer to visit the property to check the battery back-up unit is functioning normally and to replace the rechargeable batteries. It will take no more than 15 minutes to do this work and it's free of charge. If you notice a problem with your battery back-up unit at any time, you should contact us immediately on 01482 606101.

What do the lights on the battery back-up unit mean?


Battery- LED Name Colour Meaning
Status Green Mains power is on
Off Mains power is off
Fault Red Replace battery
Off Unit working correctly
Charging Yellow Charging
Off Battery working correctly



Battery - LED name Colour Meaning
Top light On Mains power is on
Off Mains power is off
Bottom Light Green Battery charging
Red Fault - Contact KCOM

Additional support

If you live in an area prone to regular power outages, you should contact us on 01482 602555 to see whether we have a better solution than a battery back-up unit.

If you're unclear on the impact this change of technology will have on you, speak to your engineer or contact us on 01482 602555. We're happy to help and provide you with any information you need.

If you have a particular reliance on your fixed line, then we're here to help. if you have a disability or specific access requirements because of your personal situation, it may be possible to obtain additional support from us. You can visit our contact us page.

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