Battery backups are intended to keep your voip service during power outages. Replacing the battery is recommended but not required. Some of our members have other means of communication like a mobile device. If you wish to replace your battery, you can do so here.
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AT&T Customer Care
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I look at things a little differently when it comes to the Belkin BBU. That box is a big help to your RG in that it not only is the power supply but also acts as a UPS. Very useful when power goes out to keep your services running. I assume you have a Pace or 2Wire RG. Keeping a good battery in there will give peace of mind as it will keep the whole UPS up and running, not just the Voice part as is the case in other RGs like the 5268 or the Arris RGs.
If you don't really care about the UPS part you can continue on without it and just use the power supply function of the Belkin, or, have ATT send you another power supply brick and just get rid of the Belkin.
100/20 Mbps VDSL2 connected Arris BGW210 gateway in IP Passthrough to Orbi RBK50 in Router mode
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