Backup Power Supply For Router! Help Needed

[haseebhm]

Hello,
I have made this 12V adapter for my Wifi router to keep it running even when the power goes off. Please see the circuit diagram located at:
http://s17.postimage.org/r47j06ejj/circuit_Ups.jpg

I connected the battery in series with a digital multimeter to determine the current in both the cases of power ON and OFF. The problem is when the input voltage is available, the current still flows through the battery in the same direction. However it is reduced from 0.45A to 0.35A.

Is it alright ? The router should take current from the power supply rather than the battery when the input voltage is available. And as far as i think, the DMM should show a current reading with the opposite sign (-) in that case because of charging. Please suggest how i need to modify the circuit to avoid this problem. Thanks.

[Nothing40]

Some current is being absorbed by the battery,to charge it.
Some is also going to the router,to power it.

To function as you describe,you'd want to add another diode in series with the battery,between battery and output jack.

However,think about what would happen when the power goes out,and the battery gets drained...how will you recharge it?
In situations like this,I usually use a resistor in parallel with the diode,to trickle-charge the battery when there is grid power available.



Personally,I'm currently running all my gear from a deep-cycle battery,and a 12V (tweaked for 13.5V) 12A SMPS plugged into the mains.(Can't set up my solar,etc. here,manager would get grumpy.) Everything runs off of the SMPS,until the power goes out,then the battery takes over. Also,when mains power is present,it keeps the battery float-charged,and ready.

I still haven't hooked up the UPS to my PC yet though. Doh.

[sadeoo7]

me all of my computer and others stuff are connected to a ups when the line power goes out the ups keep powering my things