Fault light after power outage

[Hurst32]

We have power cuts here in rural Hampshire - not often and not for long, but not infrequently either. The fibre - copper multiplex unitr usually shows a fault light for a while afterwards (as well as the charging light). This time the fault light has remained for some weeks. Everything *seems* to be working as it should but it is a minor concern. Any hints to what the cause might be or how to make it go away? TIA.

[TimmyBGood]

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@Hurst32 wrote:

 Any hints to what the cause might be or how to make it go away? 

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If FTTP broadband is working then I suspect that's the 'failure to hold charge' alert on the Battery Backup Unit, as discussed comprehensively in this thread:

https://helpforum.sky.com/t5/Broadband/Alarm-light-is-solid-red-on-openreach-box/m-p/4643571/highlig... 

Your options are to disconnect the BBU entirely (which will switch off the lower three LEDs), or to replace its four rechargeable AA cells as covered in the linked YouTube video.

As I observed in the original post the battery backup isn't doing anything particularly useful by itself because it cannot supply an ISP router with power: it can have some value if the user provides the router with a UPS, but in such a case the UPS might as well supply the ONT too as even a small lead-acid battery will have a considerably longer runtime than four AAs.