battery voltage

April 28, 2011 at 02:19:21
Specs: Windows XP
Hello,
I checked some 'dead' 3 volt batteries with a voltmeter and the reading came out at 3 volts, so how come they're not powering the devices? I thought that if they could produce the voltage then they should be able to push enough current...
Thanks for any info,
Gerard

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#1
April 28, 2011 at 02:44:33
Power is a function of voltage and current, You should test the batteries under load.

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#2
April 28, 2011 at 03:03:37
Excellent, thanks wizard-fred. I need to make up a small circuit to do that, I guess? Would just a resistor be enough? If so, what voltage and ohm ratings should I use? Apologies for my ignorance, I'm just starting out.

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#3
April 28, 2011 at 03:26:36
It depends on the device that is being powered. A coin cell for CMOS draws less than 1 ma so a 3.3K resistor will do. A camera battery would need to supply greater than 50 ma so a 47 ohm resistor would be more suitable.

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Related Solutions

#4
April 28, 2011 at 11:48:20
I've always tested cmos batteries under no-load. It may not be entirely accurate but it's good for comparing batteries. A battery with a no load voltage of 3 volts is in better condition than one say that shows 0.8 volts.

Is this a digital meter? Was the voltage showing as just 3 or somthing like 3.042? If it was just 3 you may need to change the voltage range.

What 'devices' are you trying to power up with these batteries? A perfectly good battery will appear to be dead if you try to pull more current than it can provide.

Obama's a 2012'er. That explains EVERYTHING..


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#5
April 28, 2011 at 13:04:35
DAVEINCAPS

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#6
April 28, 2011 at 13:13:27
sorry about that... DAVEINCAPS, I had two 3volt batteries in a weighing scale, it said Lo Battery, but when I tested them with the analog meter on the 10v scale they registered a little over 3v. I also had one in the computer, it kept losing the time and date but it also gave 3v on the meter. Since they're reading 3 volts, is there a way for me to know how much current they can still deliver?
Also thanks wizard-fred.

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#7
April 28, 2011 at 19:47:55
There probably is but I wouldn't know what to suggest to test them. I think you just need to buy a couple new batteries.

Could your meter be a low quality one or maybe needs to be calibrated? If possible test the batteries with another meter just to get an idea of how accurate the first one is.

Obama's a 2012'er. That explains EVERYTHING..


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