Powering adsl modem and router through 12v SLA battery


#1

A friend of mine was useing 12v SLA battery (it is usally come in emergency lights) for powering 25 wattz energy saver

and charging it with adoptor.

I am thinking to run my adsl modem and wireless route on it as both of them comsume 12v and 500 mA.

anyone have idea how it work or anyone tried it ?


#2

I am running my dsl modem and router on my 12V UPS battery. But there is a 100 watts (12V DC to 220V AC) small chinese power inverter in-between. My this technique was successful as my modem and router never got restarted again as they used to do sometimes even on the UPS.

12VDC Battery >> 100W Power Inverter 220VAC >> Modem & Router

I didnt connected the modem directly to the battery because it never gives constant 12 DC volts, it varies from 10 to 13 volts depending on charging. But you can try your technique at ur own risk, hoping it will not harm ur modem.

Also make sure while charging ur battery through a charger that your charger has capability to stop charging once charging is complete, otherwise u will end up with a exploded battery.


#3

[quote=", post:, topic:"]

I am running my dsl modem and router on my 12V UPS battery. But there is a 100 watts (12V DC to 220V AC) small chinese power inverter in-between. My this technique was successful as my modem and router never got restarted again as they used to do sometimes even on the UPS.

12VDC Battery >> 100W Power Inverter 220VAC >> Modem & Router

I didnt connected the modem directly to the battery because it never gives constant 12 DC volts, it varies from 10 to 13 volts depending on charging. But you can try your technique at ur own risk, hoping it will not harm ur modem.

Also make sure while charging ur battery through a charger that your charger has capability to stop charging once charging is complete, otherwise u will end up with a exploded battery.

[/quote]

From where u got it? and how much it cost ?


#4

[quote=", post:, topic:"]

From where u got it? and how much it cost ?
[/quote]

i bought it from Hall Road, Lahore for rs800. http://www.tbe.com.cn/ The website is in chinese but u can see the picture of it. This device will give stable 220 volts even if battery DC voltage varies from 10.5 to 15 volts (but make sure there is no built in charger in this device, my battery is charged through my UPS charger).


#5

[quote=", post:, topic:"]

I am running my dsl modem and router on my 12V UPS battery. But there is a 100 watts (12V DC to 220V AC) small chinese power inverter in-between. My this technique was successful as my modem and router never got restarted again as they used to do sometimes even on the UPS.

12VDC Battery >> 100W Power Inverter 220VAC >> Modem & Router

I didnt connected the modem directly to the battery because it never gives constant 12 DC volts, it varies from 10 to 13 volts depending on charging. But you can try your technique at ur own risk, hoping it will not harm ur modem.

Also make sure while charging ur battery through a charger that your charger has capability to stop charging once charging is complete, otherwise u will end up with a exploded battery.

[/quote]

You technique is good but there is wastage of energy during conversion.

Power inverter converts 12V to 220V, then the power adapters convert again from 220 to 9V/12V required by your modem and router.

If you are familiar with electronic circuits, you can make more efficient use of battery power, consider following setup:

12V Battery ----- DC/DC converter ------ modem and router

the DC/DC converters can be found easily in the market for around Rs 300/400. These are usually for use in cars by plugging into the cigarette lighter point and have adjustable output voltages.

Alternatively, you can replace DC/DC converter with a regulator IC circuit to have sustained output voltages. The circuit will cost you less than 100Rs and will give you 12V output even if input voltage is higher or lower. I can’t recall the exact upper/lower limits right now but I am sure it can handle ±2V variations.


#6

[quote=", post:, topic:"]

You technique is good but there is wastage of energy during conversion.

Power inverter converts 12V to 220V, then the power adapters convert again from 220 to 9V/12V required by your modem and router.

If you are familiar with electronic circuits, you can make more efficient use of battery power, consider following setup:

12V Battery ----- DC/DC converter ------ modem and router

the DC/DC converters can be found easily in the market for around Rs 300/400. These are usually for use in cars by plugging into the cigarette lighter point and have adjustable output voltages.

Alternatively, you can replace DC/DC converter with a regulator IC circuit to have sustained output voltages. The circuit will cost you less than 100Rs and will give you 12V output even if input voltage is higher or lower. I can’t recall the exact upper/lower limits right now but I am sure it can handle ±2V variations.

[/quote]

yes i agree, this is better if this plug n play device “DC/DC converter with voltage regulator” is available. And also one more feature is required in it, the low battery shutoff which is already built in the AC power inverter i mentioned above, that prevents battery damage. I didnt go for this option because my router is 7.5 volts and modem 12 DC volts.


#7

[quote=", post:, topic:"]

I didnt go for this option because my router is 7.5 volts and modem 12 DC volts.
[/quote]

Use two separate DC Voltage Regulators like 7807 (7V) or 7808 (8V) and 7812 (12V). You will have separate output for both router and modem and it will be cheap.

See this thread: http://www.wiredpakistan.com/forums/viewtopic.php?id=1085


#8

Found the info I was looking for regarding these regulator IC's. The input voltage must always be higher than the output voltage by some minimum amount (typically 2 volts). This can make these devices unsuitable for powering some devices from certain types of power sources (for example, powering a circuit which requires 5 volts using 6-volt batteries will not work using a 7805).

This means that you can power devices that need <=10VDC using 12V battery and appropriate 78xx IC.

Dropout voltage of 78xx series IC is between 2-2.5V so when 12V battery discharges to about 10/10.5V, the IC will cutoff thus preventing deeper discharge.

By the way, 12V lead acid battery gives about 14V when fully charged and at 10V, it is said to be in deep discharge state.


#9

[quote=", post:, topic:"]

Found the info I was looking for regarding these regulator IC’s. The input voltage must always be higher than the output voltage by some minimum amount (typically 2 volts). This can make these devices unsuitable for powering some devices from certain types of power sources (for example, powering a circuit which requires 5 volts using 6-volt batteries will not work using a 7805).

This means that you can power devices that need <=10VDC using 12V battery and appropriate 78xx IC.

Dropout voltage of 78xx series IC is between 2-2.5V so when 12V battery discharges to about 10/10.5V, the IC will cutoff thus preventing deeper discharge.

By the way, 12V lead acid battery gives about 14V when fully charged and at 10V, it is said to be in deep discharge state.

[/quote]

True. However, till 7808/7809, I think we can easily utilize a 12VDC source battery. For 7812 (12V DC output), one can simply put two 12V batteries or else one 12V and one 6V battery (of same current rating) in series.

Also the cut off voltage helps protect both, the battery (depending on the battery/device combination) and the device. This provides a very cheap alternative to more expensive cutoff circuits (simpler ones can possible be made with transistors - something I am just not interested in) and can get the job done at minimal cost. Obviously, as the battery gets nearer to being 80-90% charged, the output current will drop off dramatically to mer milli-Amperes. hence, while the regulator will get hot when we start charging a fully discharged battery, it will cool down later and provides an alternate way of indicating when the charging is near completion. To be more accurate, one can just put in an ammeter capable of milli-Ampere readings in series in the circuit.


#10

Hey guys know i want to know what to buy from the market

I have router and dsl modem both are 12v 500mA

I need two dry batteries 12v( I got 3 of them as i got 3 not working emergency lights)

a regulator IC circuit

what else i need?