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DC Power Supply for Wireless Camera

by leadin
Tags: amps, camera, power, supply, wireless
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Dec20-13, 07:26 AM
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I have a little wireless camera that I want to power on a battery. The camera requires 12V ~1 amp DC to run. I am a DIY kind of person and have a few lead acid batteries from work, all of them are 12V DC, but they range from 4.5 amp to 12 amp.

I've worked with AC power in the past, but not a whole lot with DC, and wanted to know will these batteries be too much?

One friend I asked, said that it doesn't matter provided they are 12V, the amps just determine how long the battery will last. Is he right?

I like this little camera and don't want to blow it up.

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Dec20-13, 08:49 AM
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Welcome to the Physics Forums.

Yes, your friend is right. The important thing is the 12 volts, then the camera will draw whatever current it needs. So long as the battery can supply 1 amp all should be good, and any lead acid battery can give 1 amp. The higher ampere-hour battery will last longer before it "goes flat". The 4.5 ampere hour battery should last about 3 to 4 hours if it starts fullycharged.

A lead acid battery when fully charged may deliver up to 14 volts, so there is the risk that a device intended to operate off 12 volts may be damaged by that higher voltage. You won't know until you try it whether your camera will find that a problem. A small voltage regulator circuit would control the voltage at 12 volts exactly.
Dec20-13, 11:24 PM
P: 1,084
Hard to imagine a "little wireless camera" drawing 1A. Are you saying that because it is specified as 1A, or you measured it, or because the supply it came with said 12V @ 1A? Not that it really matters. NasOxy is correct that you should be carefull regarding protection from > 12V.

Also, you should consider that completely draining a lead acid battery damages it (unless it is deep discharge) so you may want to protect against that also.

Dec21-13, 10:31 AM
P: 3,257
DC Power Supply for Wireless Camera

The camera requires 12V ~1 amp DC to run. I am a DIY kind of person and have a few lead acid batteries from work, all of them are 12V DC, but they range from 4.5 amp to 12 amp

Have a look at those batteries. Do they say 4.5A or 4.5AH ? If it AH then that is the capacity of the battery not the current it can deliver.

If your camera draws 1A then a 4.5AH battery should run it for 4.5 H (hours) because..

1A * 4.5H = 4.5AH

In practice in might be quite a bit less due to the age of the battery and the fact that towards the end the voltage may fall.
Dec21-13, 04:45 PM
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If the camera is to be left unattended for long periods, you can protect the battery with a cutout that disconnects the camera when the battery volts get too low. I have such a circuit on a Waeco 12V Fridge to protect the vehicle battery.
Dec24-13, 11:12 AM
P: 2
The batteries say 4.5A not Ah... also when I say a little wireless camera, I should say that I work with cameras professionally and am looking to do something that can be setup for a day and remotely viewed. Its not a little camera and that's what the tech specs state.

So basically I just have to risk it running on low power at the end of the battery. what if I wired a few batteries together to extend the life of the batteries?
Dec24-13, 02:43 PM
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So far there are a few mysteries about your question. This may be frustrating for you but we need more hard facts if you want a reliable answer.
I find it very surprising that you selection of batteries show Current and not Ah or Ahr or AHr or something involving hours. They are sold on total capacity and not Max current. The only time that battery current is printed on is for traction / starter motors and other 'big stuff'. How big are these batteries, 'physically'?
If you are into DIY then you may have a DMM and measure the actual current drain. What is the output current / volts marked on the Mains adapter? That could give a clue as to the actual current requirements. What is the model make, name and number. The spec may be available on the Web. A little solid state camera is not likely to need much current - or is it a recorder, too? Or just ask the manufacturer what they recommend.

In the OP you use the symbol ~. Do you just mean 'approximately' or is that symbol actually on the label? '~' is normally the sign for AC, when it's marked on equipment.
Failing all this, why not experiment? Connect the biggest battery you have and see how long before the volts start to sag a bit after a full charge? Don't let them go below about 11V or you will have knackered the battery you are testing.
Dec27-13, 11:17 AM
P: 245
To spell out the basics of DC supplies:

When your supply says 12V~1A that means that the supply can provide 12 Volts up to 1 amp with no problem. The amperage is a maximum. That doesn't mean that your camera draws 1 amp. Whichever engineer picked that supply decided that 1 amp was a comfortable margin for whatever amperage the camera actually draws. So we know that the camera probably draws less than an amp.

Like Sophie said, if you have the model of the camera it may be possible to get an exact figure for its current draw. Also, if you have a model # for the batteries it may be possible to dig up the Amp-Hour rating for them. In theory the run time of the camera is going to be (Amp-hour of battery)/(Amp draw of camera) for a full charge.

To answer your question, yes you can wire 12V batteries in parallel to get a longer lasting supply.
Dec27-13, 11:33 AM
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You do need to be careful with paralleling batteries. A knackered one can discharge a good one. You should use similar ones of same age, to be sure.

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