Charging Circuit....will it work?

story :

I need to provide power to my router when light is gone, i hve a laptop so dont need UPS

The adapter provides current of 1A at 9V, which means maximum power required by router is P=VI => P= 9x1 => P = 9W

A single gud rechargeable cell of 1.5v i rated 1250mAh

meaning it can provide power of P=VI => P= 1.5x1.25 => P = 1.875W

to make it 9V i will need 6 cells, which can provide power of 1.875 x 6 = 11.25W, which means i got enough power to run the router for an hour

now ive made a circuit, please temme will it work


- i will be opening the switch once the batteries are charged, or might connect a diode

- are dere chances ov router getting burned ( sum component of router getting burned )

- are dere chances adapter will burn, shud i connect a resistor to lower current flow, if yes den where and of how much ohms

Please suggest improvements to circuit, (i dont hve, multimeter, ammeter and voltmemter and nything lyk dat)

or if dares sum other inexpensive way i can provide power to router

six gud rechargeable cells are gonna cost me about 500rs

Some observations:

1 - Use a proper charger. you can damage your batteries by directly connecting them to a 9V adapter since the adapter output current might exceed the maximum charging current of the batteries.

2 - You need a regulator IC. The batteries will power the regulator and the regulator will output voltage to the router. 7809 regulators rated at 9V and 1A current are available in most electronic shops (like College Road, Rawalpindi). They will need a minimum input of 15VDC. The maximum output variation is from 8.7VDC to 9.3VDC which is quite acceptable. Note that connecting the batteries directly (as you have done in the diagram) can damage your router and/or the batteries by excessive draw.

3 - See this 9V battery eliminator circuit. The DC supply/input will be your charged batteries in series. However, you will need quite a few of the 1.5V rechargeable batteries. It is better to get two 12V wet/dry batteries and connect them in series to act as DC input. Of course, for doing this, appropriate charge mechanism should be employed.

Here's a small circuit to illustrate my post above:


dude i dont know where u live, but here in rawalpindi there is market which deals in electronics and stuff and students usually go to them to get their dld, embeded systems projects done. Guys there are freakin experts, they;ve built custom adapters / circuit boards for me from random stuff lying arnd.. i am sure u might have one of these markets in ur city.. try visiting them and tell em abt ur problem they will surely help you out

Adaptor output is 9W and you are attaching additional 11.725W load alongwith router. Isn't it going to burn the adaptor?

aalaa yaar asad cha gaye ho...actually i want to do dis myself....i will b gettin maself stuff lyk multimeter and deze commonly used electronic components like capacitors and bla bla......

waise if i make da circuit u mentioned abuv will it work perfectly and how much wud i cost me roughly

If you have calculated the load characteristics of your router properly, then there is a very good chance that the circuit will work fine. You might need to add a heat sink to the regulator just in case it gets too hot and carefully consider what batteries to use depending on the Ah rating. It would be better to try to source a regulator which can output more than 1A current - which might be slightly difficult depending on the stuff available near your place. Heat sink will be necessary in such a case.

You can add a resistor and an LED lamp between the output and the ground to indicate when the circuit is active. It shouldn't consume too much power. Select the resistance value carefully.

About the prices, it shouldn't be too expensive but if you know some electronics engineer, let him/her have a look at your circuit before you hook it up. Be prepared for some component wastage and always check the output voltage before connecting it to the router. If it works fine on initial connection, let it run and keep observing the regulator temperature. The 12V dry/wet batteries might be slightly expensive because they are already short in the market due to the prevalent energy crisis.

Edit: My router uses 12VDC at a max of 800mA. This thread is giving me ideas and if I am free next week, I will try to make a circuit to make the router run off a couple of the old sealed (dry) CSB batteries I have lying around. Should be an interesting project if I can dedicate the required time to it.

man for this kinda stuff khi is da best

if u r not familiar with circiuts the ppl in da market wil make it 4 u

students ( who dont know or dont want 2 ) actually buy there assignments in this way ( 4 unis. )

well wut ive decided is that, i will take the router wiv adapter, to an engineer whos a real expert, lives nearby and tell him what i want

+ im very near to rawal pindi, so np

just for info :

asad dewd in ur circuit ware is the DC suply from adapter ? how are the batteries going to be charged

good to see folks interested in electronics here!

You need a battery charger to charge the batteries.

For long duration backup, it would be best to use 12V battery (e.g. a car battery) coupled with a charger. Feed the battery to a DC/DC convertor like the circuit given above by Asad to obtain desired voltage and feed that to the router. Simple block diagram

A/C Supply ---> Battery Charger ---> 12 V Battery ---> DC/DC conv.----> Router

An added advantage is that you can add a few more low wattage devices e.g. your DSL modem to the chain.

A/C Supply ---> Battery Charger ---> 12 V Battery ---> DC/DC conv.----> Router

+---> DC/DC conv.----> DSL Modem

If the device works on 12V then you don't need DC/DC convertor.

ive already got a heavy duty 220v ac to 12v dc conertor, all i need now is vrag capacitors nd BATTERY(most expensive thing), well wuts da price of cheapest available 12v batt., wet and dry ?

++ hw much is dis vrag goin ta cost ?

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

asad dewd in ur circuit ware is the DC suply from adapter ? how are the batteries going to be charged

You will need a normal 12VDC output adapter which can give you adequate current too. Hook it up to an ammeter in series and connect to the batteries (again in series). For reference, look up the data sheet of your battery for maximum charging current. A 4.5AH battery is usually charged at 1A continuous supply.

And Vreg (not Vrag) stands for Voltage Regulator.

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

++ hw much is dis vrag goin ta cost ?

Inquire about 7809 1.5 to 2 Ampere regulator. I reckon it would cost from Rs.10-30 depending on quality, brand name and the current rating.

Use two 12V batteries of motorbike, they are cheap and easily available. They can easily keep your router up for many hours.

i wana ask to asad dat is it possible i have a psp usb charger wd me if i cut its wire and hoook it to my router by joinin wires will it work seems like crazyy to me

Eh? PSP?

ya its a usb plug charger just plug it in usb and onto ur psp charging slot so it will charge ur psp via.

Oh... That PSP... :o

Anyway, USB only provides 5V and the current is also quite low. Routers run at voltages greater than 9V minimum. I don't think it will work.

thhhx asad not ripping it now :) well got 12v wet batter and a resistance heat sink which converts it to 9v made by my friend its workin for me now :)