Can we make an adsl modem work with battery.

[98formulaLS1]

No.

No.
The Energizer 9V alkaline battery has a capacity of 625mAh when its output voltage has dropped to 4.8V and the current is only 25mA. The capacity is only 275mAh at 500mA and much less at 1A.

A 9V alkaline battery has a pretty high internal resistance so it will not have 9V at 500mA and its voltage drops very quickly. The voltage will be at 7V in a few minutes.

yes, thank you for correcting me.

 

[pxjain]

I am overwhelmed by so many of responses . But I am still not clear as to which one of the following AC adapter is a better choice to connect to a modem requiring 9V 1A AC input?
1) The adapter with constant 9V and rated 3.2 Amps
2) Or the adapter with variable voltage (5V, 9v, 12V) and 1 Amps rating.

Also some of you are suggesting that I can connect the modem to a 12V DC source. If this is true, how do I connect a DC supply to the modem? The modem accepts AC and hence does not have a +/- terminals, where as the DC adapter have +/- terminals.

 

[mvs sarma]

I really feel that the posts are put without exactly referring to info the poster has with him and the discussion prolongs borad and wide. for example the Op , an year back referred to a Modem. had it, he also had the data about the psu poweringit. he could well do it.
even PXjain just says Dlink 502-T but he doesn't talk about the spec of the supply that came with the modem except that "it says 9V AC". the handbook clearly mentions. I fear these discussions lead us no where .

 

[pxjain]

PXjain just says Dlink 502-T but he doesn't talk about the spec of the supply that came with the modem except that "it says 9V AC".

The spec of the power supply as defined in the manual
Input: 110v - 240v AC 50 ~ 60 Hz
Output: 9V, AC, 1A

 

[mvs sarma]

The spec of the power supply as defined in the manual
Input: 110v - 240v AC 50 ~ 60 Hz
Output: 9V, AC, 1A

as such a simple transformer at240V input (not 230) and output at(V with 1.56 amps works for you, safely. the input to the transformer can be from UPS supported mains supply. if the UPS, Stabilizer are all relay switched ones, the changeover times cause modem drops. while the PC PSU takes care of such momentary breaks, a Modem with 9v AC input may not. we also have issues with even APC make UPS.

 

[pxjain]

as such a simple transformer at240V input (not 230) and output at(V with 1.56 amps works for you, safely.

I infer from this that the adapter that outputs 9V AC and rated at 3.2A is not good. I needs to have an adapter that outputs 9V AC and rated at 1.56A.

 

[mvs sarma]

I infer from this that the adapter that outputs 9V AC and rated at 3.2A is not good. I needs to have an adapter that outputs 9V AC and rated at 1.56A.

It is also Ok
as the load will not draw that much current.

 

[audioguru]

A transformer that is rated for a higher current will operate cool at the lower current used by the modem.
A transformer that is rated at the 1A current used by the modem will be at its max allowed temperature. It will be too hot if the mains voltage is high and if the ambient temperature is high.

 

[pxjain]

A transformer that is rated for a higher current will operate cool at the lower current used by the modem.
A transformer that is rated at the 1A current used by the modem will be at its max allowed temperature. It will be too hot if the mains voltage is high and if the ambient temperature is high.

Thanks a lot audioguru. This is exactly what I was after. I will now go ahead and buy 9Volt, AC, 3.2A adapter.

 

[Diver300]

Thanks a lot. I will first look into the modem to see, if I can take the diode bridge out so that its ready for accepting DC input.

Am I expecting a diode bridge or just two diodes inside the modem?

You might not have to bother at all.

A lot of small electrical device have bridge rectifiers inside them, and they are designed to run from AC.

However, they will usually run perfectly well from DC. If that is the case, a 12V battery will have almost exactly the right voltage to match the peak of a 9V AC supply.

Some devices might need an alternating supply, but it is worth trying 12V (via a fuse). If it works, a sealed lead acid battery will be fine, or a nice switch mode 12 V DC supply that won't mind the voltage variations.