Jump to content
Sign in to follow this  

PowerSupply UPS over voltage

Recommended Posts

Hi guys,


I've just bought a power supply with UPS, model: "PD-240-18-UPS" which runs on batteries when main power runs out.

That device is supposed to draw 12v DC output on all terminals to supply power to cameras and whatever is behind, but it draws 12,90v DC. That over voltage is more than a -/+5% and I am worried that this might cause issues to the DVR and some cameras that are being powered with it. The onboard voltage regulator is already set to the minimum.


I have added a resistor in one of the outputs to reduce the voltage to 12,40v, but if so the DVR won't start (I'am guessing that the resistor is consuming so much amperage that the DVR can't even start).


Extra info:

-The DVR consumes 2A and each camera 1A or less.

-If I use a diode to reduce 1V, it will introduce undesired voltage fluctuations which may be even worse.

-I've connected up to three voltage output in parallel (to increase amps.) with the resistor and the DVR won't power up. If i remove the resistor, it powers up with just one voltage output.

-When main power is out and runs on batteries, 12v are supplied to all output terminals.

-I've connected the DVR directly to the power supply, so it is very close. Cameras are not that far (15 mts wt. UTP)

-I use analog D1 cams


Any thoughts ?


Thanks for your help,

Share this post

Link to post
Share on other sites

I suspect you worry over nothing. Check your camera and DVR specifications to see what they will accept as a nominal 12V.


If you must have a voltage dropper, use a BY550 or similar diode in series, it will drop a 0.6 volt or so. Don't mess with resistors, won't work (just as you have found).

Share this post

Link to post
Share on other sites

As Rossko has pointed out the 12V is a nominal working voltage and you will likely find that anywhere from 10 -14 V it will work fine. I'm intrigued about the statement that a diode will cause voltage fluctuations - can you elaborate

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this