low power battery backup

[jimandy]

Haven't been here in a while but I appreciate the new login measures as the spam was really bad when I last visited.
Here's the issue. Have a new cordless phone/answer machine. Did not know when I got it that it won't retain the OGM and security settings if the power goes off making it necessary to re-program every time we have a power loss. It runs on a small 6VDC wall-wart Was wondering if there is available a lower power module that would hold up the 6 volts with 4 AA batteries for a few minutes when we have these short power interruptions. Seems like it would just take a diode and the battery clip hardware but I'd rather a ready made one on-the-shelf.
Thanks for any suggestions.

[sghioto]

Seems like it would just take a diode and the battery clip hardware

That might be the best solution considering cost. Just make sure the output from the adaptor is higher or at least equal to the battery voltage or the phone will drain the battery pack.

Another possibility is using a "super cap" a very large value capacitor (at least 100,000 uf) isolated by a diode on the output of the 6 volt adaptor. Depending on the load current this may hold the voltage for several minutes.

Steve G.

[MrAl]

Hi there,

Sounds to me like all this calls for is two diodes, a battery holder, and some connectors and some soldering.
One diode for the wall wart (if it draws current back into it when externally powered with DC) and one for the battery pack. A couple connectors to stick it all together neatly and you're all set.

I could draw up a schematic if you need one.

[jimandy]

Thanks Steve and Mr. Al.
Yes, I was thinking of putting it together but was hoping there was such a thing already out there in the market place. Would be especially nice if the batteries were rechargeable.

[Janitor Tzap]

Hey jimandy,

I known what your looking for, because a friend had one for his cordless phone.
Thus, when he lost power he still could make and receive calls.
But they are not all that cheap.
Here's one from South Western Bell.
http://www.google.com/products/catalog? ... CF4Q8wIwAA

Hope that helps.


Signed: Janitor Tzap

[ringo47stars]

They are pretty common in theory like if you unplug your computer the battery takes over. Battery back-up for the phone was not too popular until recently because of the ripple caused by using the phone from the output of the charger. I don't know if you can find one commercially because of the diverse specifications of the out-put. To make one you just use the batteries while on the charger and turn the charger off when the batteries are charged or turn the batteries off when they are charged depending on your preferences. Put a large cap in there to hold the power until the batteries take over,like sghioto said, would be a good idea. Battery powered chargers for AA's are common but you'd have to experiment with them to see if the ripple from the modulating circuit is acceptable. I got an error message when I went to that link from janitor tzap but that could be my computer.

[Janitor Tzap]

I got an error message when I went to that link from janitor tzap but that could be my computer.

It may be your computers browser filter blocking you.
I just went to Google, and in search I put in: "CordLess Phone Battery Backup".
That link was just one of the many results.


Signed: Janitor Tzap

[MrAl]

Hi,

Just to note, i have read now that some of the commercial back up supplies for cordless phones do not work with ALL phone models. You would have to make sure the unit you buy works with your particular phone.

[Janitor Tzap]

Hi,

Just to note, i have read now that some of the commercial back up supplies for cordless phones do not work with ALL phone models. You would have to make sure the unit you buy works with your particular phone.

Very true.

But from the information that jimandy supplied.
I believe something like this would work.
http://www.google.com/products/catalog? ... tech-specs


Signed: Janitor Tzap