modem on battery backup

All telephone modems have (by law) a battery backup for the telephone, but NOT for the internet. "Ah ha", you think, "I'll just put the modem on a UPS!" But it turns out that the "telephony modem" will not charge the battery fully if the power source is on (some) UPS.

Has anyone found a way to keep the internet connection going during a power outage and STILL charge the telephone battery backup?

Reply to
me again
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I don't see how it could tell the power came from a UPS or the powerline unless your UPS doesn't have a decent waveform that it can somehow detect. To be honest, the wall-warts these things use shouldn't notice the difference.

Reply to
Andrew Rossmann

I do believe the "party line" is (somehow) correct as I have had the modem connected to a UPS for YEARS with 2 batteries in the modem and the ride-through should have been close to 8 hours but it only lasted 1 hour. Furthermore, after power restored the Comcast callcenter said my battery was showing 100%.

I have heard before (but remember little) that one UPS plugged into another UPS is a bad idea because of the nature of the waveform created by #1 is analyzed by #2.

I suppose the solution is simply to remove (both) batteries from the modem and rely solely upon the UPS!

Reply to
me again

After "years" of use I would suspect that the battery is not working at its full potential any longer. That might explain why it lasted 1 hour instead of 8.

Reply to
Bill M.

Now that it has been on "line" for a couple of days, maybe I should just pull the plug and see how long it lasts. Wait, that would disconnect my internet!

Reply to
me again

People have been known to survive short periods of time without Internet, so it's not as risky as it seems.

Reply to
Bill M.

What model modem (or actually, eMTA) is it? Does it actually have 2 batteries? Do both work? I thought most just had one supply that ran both the phone and internet. It's a bit odd that it may have 2 separate supplies.

Reply to
Andrew Rossmann

In the eMTAs I've had from Comcast, the internal battery operates phone but not Internet. They have room for two batteries, typically, but Comcast supplies one. I've never had two models that share the same battery.

UPS would be the only solution to maintain Internet access.

Reply to
Adam H. Kerman

But it turns

power source

Surely you jest!

Reply to
me again

Yes, but the installer gave me two because I asked.

'fraid so!

Reply to
me again

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