6 Replies Latest reply on May 15, 2016 11:35 AM by inception007

Power Circuit needed

Dear All, I am looking to connect my adsl modem(12 V, 1A) directly to 12V ,30 A battery.

Kindly suggest me a simple and the best method to control the large current flowing from the battery to avoid my modem power cirucuit from burning.

• Re: Power Circuit needed

Hi,

Considering that your battery is just a battery, so DC, you need to know if the 12V of the modem are DC (some adsl modems needs AC input), about the 30A of the power supply, that means that the battery can give up to 30A, but it will only give tha amps needed by the modem, in spite of, this I recommend you put a fuse protection.

Hope that helps

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• Re: Power Circuit needed

My modem need 12 V DC. Directly connecting modem to battery work fine but burnt one. Few models worked fine i tested it , but I think i need some sort of current controlling device (JUST LIKE voltage regulator for voltage ) bcz dc battery mostly keep its voltage constant but not current, and at the start battery give larger current. Fuse is a good option but would be better if come up with current controller , that keeps the current to constant to 1A ,not shutting the electric current down like fuse when rises above 1A.

• Re: Power Circuit needed

In this situation it is mostly the voltage that matters. Your modem will draw no more than 1A as long as the battery supplies no more than 12 V. In other words your 12 V  modem will not have any problem using a 12V battery as its power supply. The fact that the battery can supply 30 A is good - it means it will not be stressed when it is only supplying 1 A. It is a good idea to put a fuse on the battery power wire at the battery to protect your wiring in case a short circuit accidentally occurs downstream. If your battery puts out a voltage higher than 12 V, you need to determine if your modem can handle the higher voltage.

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• Re: Power Circuit needed

Mostly that work but for few models that burnt the voltage regulator chips inside the modem.

I want to avoid risk and connect my other modem to battery without any hesitation.

Hope you will solve my problem.

• Re: Power Circuit needed

It sounds like your modem doesn't really need 12V and it tends to overheat if it has 12V, especially since most 12V batteries have a higher voltage than 12V.

If 12V is its maximum, what is the minimum voltage it can work at?

You can try using a 10V voltage regulator which has a 1A current limit - just make sure it has enough heatsink to dissipate several watts.

Another potential solution is to use a PTC (positive temperature coefficient) fuse.

You might even try a power resistor in series.

You might try putting a better heatsink inside your modem on the chips that are burning.

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• Re: Power Circuit needed

Thanks, I will try that , will use voltage regulator followed by PTC fuse... Will let u know then..