Can we make an adsl modem work with battery.

[pxjain]

Is this +9V 0 -9V adapter same as a regulated 9v DC adapter found in the market? What about the Amp rating? I guess it would not matter if its a regulated dc adapter?.

Also would the regulated dc adapter will be fine providing 9V even when the voltage drops to 170-180V?

 

[audioguru]

A transformer is supposed to have the correct mains voltage.

A 9VAC transformer has an output voltage of 9VAC when its load is as rated. Your 3.2A transformer might have a voltage of 9.4VAC when the load is only 1A and it will be cool.

 

[ericgibbs]

Is this +9V 0 -9V adapter same as a regulated 9v DC adapter found in the market? What about the Amp rating? I guess it would not matter if its a regulated dc adapter?.

Also would the regulated dc adapter will be fine providing 9V even when the voltage drops to 170-180V?

You would have to design a psu that gives +/-9Vdc when the mains supply is at say at 170Vac... if the mains rises to say 240Vac then the power supply would have to cope with higher dissipation in the regulators etc.

You could look thru the web for an SMPS with 170v thru 240V input , with the required +/-9Vdc output

 

[pxjain]

Does this mean, I don't need to get into the modem, but can simply plug in 9V 3.2A AC adapter?

Your 3.2A transformer might have a voltage of 9.4VAC when the load is only 1A and it will be cool.

The 9.4V is just an estimate or there is some calculation behind it? Some where I read that a 9V AC to DC unregulated adapter rated at 3.2A will give 9*3.2V if only loaded at 1Amps. It did not make sense to me and from your answer of 9.4V, I have more reasons to believe that is untrue.

 

[pxjain]

You could look thru the web for an SMPS with 170v thru 240V input , with the required +/-9Vdc output

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?

 

[audioguru]

Why are you talking about a DC adapter? You don't know where inside the modem to connect it.

9V*3.2A= POWER, not voltage.

A low power 9VAC transformer is 100mA. It has an output of 9VAC when its load is 100mA. It is cheap so its internal resistance is high which causes its voltage to be maybe as high as 18V without a load.

A 1A transformer has a voltage that rises less when its load is less than its rating.

A 3.2A transformer will have a voltage that rises even less when its load current is less. But I don't know if an Indian transformer will have the same quality as a Canadian transformer.

 

[ecerfoglio]

I have an adsl modem and i have was just wondering if i can use a battery to make it work. The power rating of my modem is 9V DC and 0.5 A.

Now the question:
1) Do I have to connect a battery providing current exactly 9V, 0.5A?

The reason some of these modems require 9Vac as an input, is because of the RS232 voltage level requirement.
The modem internal diodes half wave rectify the 9Vac to give ~ +9Vdc and ~-9Vdc.

Nowadays adsl modems don't use RS232 interfaces, they use either Ethernet or USB.

USB modems are ussually powered from the host computer via the USB cable, while Ethernet modems need a separate power supply. I think that this is the case with shareebacha's modem.

Shareebacha:

You should use a 9V (DC) adapter or power supply capable of at least 0.5A, preferably a regulated one

If you need batteries, you can use a 9V battery of as many ampere-hours (Ah) as the time you want it to operate times 0.5A - (eg a 6 Ah battery (= 6000 mAh) will give you 12 hours of operation).

Or you can use a 12 V battery plus a 9V regulator (like a 7809). This will give a constant voltage even if the battery is fully charged (up to 15 V) or if it discharges to aproximately 11 V.

 

[mvs sarma]

Hi

I am trying to solve a similar issue and needs advice of experts here.

The Chinese modem supplied by the broadband provider BSNL (India) has issues with its AC adapter. If you leave it on for couple of hours it gets very hot and if you leave it on for couple of days, it will burn.

The AC adapter outputs 9V AC and rated at 1 Amps. I replaced the Chinese modem with D-link 502t, recommended by the local supplier. The D-link modem also came with 9V AC and rated at 1A. I suspect the Chinese modem is a copy of the D-link as the web administration is exact the same. However the D-link adapter didn't last for more than couple of weeks.

I think the voltage fluctuates quite frequently and hence cause these adapter to burn. I am looking for a solution to power up my modem, which requires 9V AC 1Amp and can work under voltage ranging between 170V to 240V.

I couldn't find any 9V AC to AC adapter that are regulated. Is there any thing like AC to AC regulated power adapter?

I was thinking of buying a 230V AC to 9V 3.2Amps AC adapter. Will it work with the modem that requires 9V 1Amp AC as input?

The reason I want to go with a higher Amp is so that it does not get hot. Am I thinking right?

Please advice.

Thanks in advance

I am one retired from the same BSNL and did lots of serving
I don't get to know what is your trouble at all. you can supply 12V regulated DC with a capacity of 1 amp or 1.5 amp. the Huwawei and UTstar modems are HOT
but your concept that the temp growth curve is steep and it would burn is not correct. we can't compare our tropical climates with European, American or Canadian situations. they have AC in their homes. with scorching 40 Deg Celsius and trying to work a modem will impair it, so better to work the modem in an AC room or at least cooled room(with its own problems of High rel humidity)
i have used Huwawei MT841, UTstar wa3002-G1, and UT300R2U. they are hot but never died. BSNL of late is supplying locally developed 12V SMPS adopters of Axium or similar makes. unless faulty, the supply id reasonably good.
however your initial quesry whether you could opearte the Modem with12V DC-- YES
it helps you work with lap top even under power failures.

 

[pxjain]

Why are you talking about a DC adapter? You don't know where inside the modem to connect it.

I was just trying to follow up the suggestion made by all the experts here. I would feel more comfortable, if I don't have to open the modem and your explanation about voltage rise seems good to me.

I am buying the 120V AC to 9V AC (3.1A) adapter from **broken link removed**, which is a reputed company in the UK with high street stores and hence I hope that the adapter is of good quality.

There is another variable voltage 1 Amp AC 2 AC adapter **broken link removed**. Not quite sure which one is better for my use.

 

[pxjain]

you can supply 12V regulated DC with a capacity of 1 amp or 1.5 amp. the Huwawei and UTstar modems are HOT
but your concept that the temp growth curve is steep and it would burn is not correct.

It were the adapters that got burnt. I had 3 of them that got burnt. Some how we had two BSNL modems and then we bought the D-Link 502t. All the three adapaters turned into smoke. We also have the CVT and UPS connected, but someone said that the CVT causes the adapter to burn. Since then the CVT (costed us Rs.6000) is setting in the basement somewhere. I know quite a few other guys in the town whose adapter got burnt. We could not find a good replacement locally and had to be dependent on a local electrician to bind the transformer again. So my dad's broadband connection is living dangerously on a locally binded transformer.

From this I concluded that may be I need a tranformer with higher rating. All my other devices such as router, VOIP ATA (SPA-3102) that I bought from UK works fine. But the adapter on the BSNL modem will not work.

BSNL of late is supplying locally developed 12V SMPS adopters of Axium or similar makes. unless faulty, the supply id reasonably good

Can I get hold of these adapters. Becasue these is the biggest problem to run the broadband, which otherwise is quite fast and good.

however your initial quesry whether you could opearte the Modem with12V DC-- YES
it helps you work with lap top even under power failures.

The modem says 9V AC. So Can I connect them with a 12 Volt regulated DC (3+ V higher)? Will it work?

Also with BSNL broadband, can I use any other ADSL modems? If so which one do you recommend? I just need a modem that can be bridged as I need public IP to pass through the modem. My dad lives in Kishanganj, which is in Bihar. And I am not sure but I think we were originally supplied with UTstar modem. One thing I am sure of is that the web administration page of the BSNL supplied modem was exactly the same as the D-link 502T.

 

[mvs sarma]

I was just trying to follow up the suggestion made by all the experts here. I would feel more comfortable, if I don't have to open the modem and your explanation about voltage rise seems good to me.

I am buying the 120V AC to 9V AC (3.1A) adapter from **broken link removed**, which is a reputed company in the UK with high street stores and hence I hope that the adapter is of good quality.

There is another variable voltage 1 Amp AC 2 AC adapter **broken link removed**. Not quite sure which one is better for my use.

i can tell a simple way, use a manual voltage corrector with a switch. set it to 180 V , connect your modem power supply and leave it in the nights. no problem will come

not needed
the modem has an input bridge rectifier


Please tell me the make and model number. i will get you the internal photograph.You don't waste money purchasing components and paying international couriers. At least India is that capable of making a good small power supply.

 

[pxjain]

i can tell a simple way, use a manual voltage corrector with a switch. set it to 180 V , connect your modem power supply and leave it in the nights. no problem will come

not needed
the modem has an input bridge rectifier


Please tell me the make and model number. i will get you the internal photograph.You don't waste money purchasing components and paying international couriers. At least India is that capable of making a good small power supply.

Thanks a lot. Being a very proud Indian, I am well aware of the how efficiently and cheaply things can be done in India. e.g. the electrician only asked for Rs.100 (£1.5) to open the transformer and redone it.

But until now, it was quite difficult to know what will work? I tried 4 different adapters (in India), each of them costing around Rs.500, but none of them worked.

What is a manual voltage corrector? Is is the same as regulator that we use for fridge? I have tried that, but the adapter got burnt. I know lot of people in Kishanganj, whose adapter got burnt and as BSNL does not supply spare ones (at least in Kishanganj), they had no choice but to buy D-link 502t for Rs.2000.

The modem that we have have got is D-Link 502t and the BSNL supplied is possibly UTstar.

Thanks a lot for your quick response. I hope I will be able to solve the adapter issue. The amount of money and time I have spent on this issue that I am prepared to pay another £10-20, if I can solve this ones and for all.

But so far I am not clear what to do. Will the 9V 3.2A AC adapter will work with these modems?

 

[mvs sarma]

Thanks a lot. Being a very proud Indian, I am well aware of the how efficiently and cheaply things can be done in India. e.g. the electrician only asked for Rs.100 (£1.5) to open the transformer and redone it.

But until now, it was quite difficult to know what will work? I tried 4 different adapters (in India), each of them costing around Rs.500, but none of them worked.

What is a manual voltage corrector? Is is the same as regulator that we use for fridge? I have tried that, but the adapter got burnt. I know lot of people in Kishanganj, whose adapter got burnt and as BSNL does not supply spare ones (at least in Kishanganj), they had no choice but to buy D-link 502t for Rs.2000.


The modem that we have have got is D-Link 502t and the BSNL supplied is possibly UTstar.

Thanks a lot for your quick response. I hope I will be able to solve the adapter issue. The amount of money and time I have spent on this issue that I am prepared to pay another £10-20, if I can solve this ones and for all.

But so far I am not clear what to do. Will the 9V 3.2A AC adapter will work with these modems?

a manual voltage stabilizer as used on fridge etc, it has an UP or DOWN switch and another rotary switch with 5 steps.
Please have one and keep it in DOWN position wand adjust rotary switch to have 10V output . use this 180 to the adopters etc. i fear that most of your failures are during night times when the voltage reaches high as 275V. these transformers (12V Ac or DC adopters) start cooking their electrolytic caps inside.

 

[pxjain]

a manual voltage stabilizer as used on fridge etc, it has an UP or DOWN switch and another rotary switch with 5 steps.
Please have one and keep it in DOWN position wand adjust rotary switch to have 10V output . use this 180 to the adopters etc. i fear that most of your failures are during night times when the voltage reaches high as 275V. these transformers (12V Ac or DC adopters) start cooking their electrolytic caps inside.

The manual voltage stabilizer has a manual rotary switch to set the input voltage between 170 to 220 Volt.which gives 220 volt output. I have not seen any of them that gives 10 volt output. Do you mean then plug a 10V adapter to its output? Can you please explain?

Many Thanks

 

[mvs sarma]

The manual voltage stabilizer has a manual rotary switch to set the input voltage between 170 to 220 Volt.which gives 220 volt output. I have not seen any of them that gives 10 volt output. Do you mean then plug a 10V adapter to its output? Can you please explain?

Many Thanks

exactly !!
the output would be used to power all your equipment so that night high voltages don't burn the equipments. they are manual stabilizers and are cheap

 

[pxjain]

exactly !!
the output would be used to power all your equipment so that night high voltages don't burn the equipments. they are manual stabilizers and are cheap

Thanks a lot

So just to clarify, the steps to follow now are

1) Connect a manual/automatic regulator/stabilizer to the wall socket
2) Connect the 9V-10V AC adapter to the output of stabilizer
3) Power the modem with the adapter.

However I also have a UPS connected to ensure that every thing is powered up between the power failure and the generator is started. Where does the UPS fit in this scheme? Before the stabilizer or after the stabilizer?

Also in terms of the AC adapter - which one is better choice
1) The one with constant 9V and rated 3.2 Amps
2) Or the one with variable voltage (5V, 9v, 12V) and 1 Amps rating

 

[audioguru]

Why doesn't your electrical utility company adjust the voltage so it is correct?
Mine does.

 

[mvs sarma]

Why doesn't your electrical utility company adjust the voltage so it is correct?
Mine does.

We had enough discussion on the power subject. neither we can come and live in Canada, nor India or any other country can become Canada or US overnight. Let us find ways to manage the situation. Perhaps more important is equipment survival in the prevailing conditions.

 

[98formulaLS1]

wow, so much discussion over something too simple. As engineers, we tend to over complicate things. Let me give you the straight simple answer.

If your wall adapter outputs 0.5A @ 9V, then a 9V battery connected with the proper polarity to the input power connection of the ADSL modem will work just fine.

Now, you want to know how long the battery will last. Well, becuase batteries are rated in milliamp hours and they have a much larger error tolerance, batteries can only be said to be reliable for 70% of their rated life minimum.

So, typical 9V batteries are rated at ~700mAH, dispite what the gentlemen earlier said. if you don't believe me, check the technical specs from energizer and duracell.

So the equation is (current of the battery / current being drained)*0.7 = (700mAH/500mA)*0.7 = 0.98 hours.

SO, this means that connecting a standard alkaline 9V battery to your ADSL modem will reliably power your modem for AT LEAST about an hour. Anything after one hour is unpredictable.

Remember this, an battery cell is only ~1.5v, thus there are 6 cells in one 9V. If you remember, cells connected in series only sum the voltages, while the total current remains the same as an individual cell. So 1200mAH from a single alkaline cell would be impressive.

 

[audioguru]

If your wall adapter outputs 0.5A @ 9V, then a 9V battery connected with the proper polarity to the input power connection of the ADSL modem will work just fine.

No.
The adapter has a 9V AC output. The peak voltage is 12.7V and the rectifier bridge reduces it to 11.3V which is the DC inside the modem. We don't know if the modem makes a negative supply from the AC in addition to the positive supply.
The modem uses 1A, not 0.5A.

Now, you want to know how long the battery will last. Well, becuase batteries are rated in milliamp hours and they have a much larger error tolerance, batteries can only be said to be reliable for 70% of their rated life minimum.

So, typical 9V batteries are rated at ~700mAH, dispite what the gentlemen earlier said. if you don't believe me, check the technical specs from energizer and duracell.

So the equation is (current of the battery / current being drained)*0.7 = (700mAH/500mA)*0.7 = 0.98 hours.

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.