Paranormal Battery box

[Jyera]

I have a plastic battery box with an on-off switch.
It can hold 4 AA size 1.5V batteries to give a 6V voltage source.

I placed some batteries in it. These are not new batteries.
When I turn it on and measure it with a digtal multimeter, it shows around 4.4V. When I turn off the switch, it shows 1.46V on the multimeter.

Weird!??!

I would have thought that it should show zero because it is an open circuit.

Why?

 

[PixyMisa]

The switch is what is known in the trade as "stuffed". It's leaking current. There's some crud in there that is conducting electricity even when it is nominally open.

 

[teddygrahams]

The numbers look suspicious to me. Is it possible it's switching between 3 cells in series and the remaining cell ?

Take the batteries out and beep out the connections.

 

[PixyMisa]

Yeah.

If it's a half-way decent multimeter, set it to measure resistance and have a play around with the various contact points.

 

[bruto]

I think teddy has it. If it's a new box, there's a possibility they just wired it wrong. Also make sure the batteries are right way round. Not all battery cases are intuitively arranged. I've seen some, for example, that put three batteries in one direction and the fourth in the other, etc. My cheap wireless keyboard here takes 2 AA's, and uses the coil spring contact you usually see going to the negative end as the positive on one of them, a confusing visual cue.

 

[Jyera]

I had measured each batteries to be around 1.1V to 1.2V.
The 1.46V doesn't seems to be the voltage of a single battery.
If the switch is on, and I measured the voltage progressively, it seems to register the correct voltage of 1.1V, 2.2V, 3.3V, 4.4V. So I think it is not wired wrongly.

Further more I have tried this:
Turn the switch to off. Removing one of the four batteries.
I remove the battery which is furthest from the the switch within the series.
And measure the voltage. Result 0V.
In this case, I have 2 apparent breaking of the circuit; one via the switch and one via the removed batteries.

 

[Jyera]

The switch is what is known in the trade as "stuffed". It's leaking current. There's some crud in there that is conducting electricity even when it is nominally open.

Is it very common to have "stuffed"? Why would it be leaking current ?
It would seems to be against the notion that open circuit do not allow current to flow.

 

[PixyMisa]

Is it very common to have "stuffed"?

Yes.

Why would it be leaking current ?

Because there is something in the switch that is providing a path for the current even when it is nominally off. But that something isn't a very good conductor, so you only get a fraction of the voltage.

It would seems to be against the notion that open circuit do not allow current to flow.

The circuit isn't open. Obviously.

 

[bruto]

I had measured each batteries to be around 1.1V to 1.2V.
The 1.46V doesn't seems to be the voltage of a single battery.
If the switch is on, and I measured the voltage progressively, it seems to register the correct voltage of 1.1V, 2.2V, 3.3V, 4.4V. So I think it is not wired wrongly.

Further more I have tried this:
Turn the switch to off. Removing one of the four batteries.
I remove the battery which is furthest from the the switch within the series.
And measure the voltage. Result 0V.
In this case, I have 2 apparent breaking of the circuit; one via the switch and one via the removed batteries.

If the batteries are correctly inserted, and the case correctly wired, in series, you should get 0 volts if you remove any one of the batteries. If this is not the case, look for a problem in the wiring of the series. If this is the case, then there is some path of resistance parallel to the switch (i.e. the switch is probably stuffed).

 

[Elind]

I had measured each batteries to be around 1.1V to 1.2V.
The 1.46V doesn't seems to be the voltage of a single battery.
If the switch is on, and I measured the voltage progressively, it seems to register the correct voltage of 1.1V, 2.2V, 3.3V, 4.4V. So I think it is not wired wrongly.

Further more I have tried this:
Turn the switch to off. Removing one of the four batteries.
I remove the battery which is furthest from the the switch within the series.
And measure the voltage. Result 0V.
In this case, I have 2 apparent breaking of the circuit; one via the switch and one via the removed batteries.

If you have a multimeter, why have you not checked the resistance across the switch when open?

If that shows open circuit, take out the batteries and with the switch still open check resistance from the suppy side (not the battery side) of the switch to the battery terminal points in turn. There could also be a short in the last three positions closest to the switch (not the first one) direct to the supply lead.

 

[Jyera]

The fact that the voltage changed when I switched it from on to off, created the impression that it is indeed working and "opening the circuit".

It didn't occur to me that the switch might behave like a resistor.
I was a little hung up about the possibility that it might be behaving more like a capacitor.

Will go measure the switch for resistance.
But what is the frequency of a "stuffed" switch behaving like a capacitor.

 

[Elind]

The fact that the voltage changed when I switched it from on to off, created the impression that it is indeed working and "opening the circuit".

It didn't occur to me that the switch might behave like a resistor.
I was a little hung up about the possibility that it might be behaving more like a capacitor.

Will go measure the switch for resistance.
But what is the frequency of a "stuffed" switch behaving like a capacitor.

No capacitance possible from that type of device. If it were you would see the voltage slowly, actually quickly, drop to zero from the start level.

 

[Jyera]

Without the batteries in the battery box, I measured the resistance of the (open/off) switch. I put the multimeter to it's highest resistance measure of 2M Ohm. Result, out of range. This usually means open circuit. But still it could mean very very very high resistance.

What I did next gave me the biggest surprise yet.

I measured the voltage of the switch in the open/off position, without the batteries in the battery box. And to my surprise !!! It shows a voltage, 2 mV.
And the voltage did not go to zero.

No battery and yet there is a voltage ??!!?

 

[Elind]

Without the batteries in the battery box, I measured the resistance of the (open/off) switch. I put the multimeter to it's highest resistance measure of 2M Ohm. Result, out of range. This usually means open circuit. But still it could mean very very very high resistance.

A very very high resistance is equivalent to an open circuit in this case, and would not allow you to measure 1.49 volts even if it were not infinite. The switch is OK.

What I did next gave me the biggest surprise yet.

I measured the voltage of the switch in the open/off position, without the batteries in the battery box. And to my surprise !!! It shows a voltage, 2 mV.
And the voltage did not go to zero.

No battery and yet there is a voltage ??!!?

That's the voltage, 2 thousands of a volt, generated either by the sweat in your socks or the fluorescent lights in your garage. Try sticking one end in your mouth and another somewhere else, and see what you read

Your box appears to have a short that bypasses the switch. Did you measure those paths?

 

[PixyMisa]

Without the batteries in the battery box, I measured the resistance of the (open/off) switch. I put the multimeter to it's highest resistance measure of 2M Ohm. Result, out of range. This usually means open circuit. But still it could mean very very very high resistance.

Okay, bang goes that idea.

If it was conducting but above 2M Ohm, the voltage would be tiny, so we can be comfortable that that's not it.

 

[bruto]

Without the batteries in the battery box, I measured the resistance of the (open/off) switch. I put the multimeter to it's highest resistance measure of 2M Ohm. Result, out of range. This usually means open circuit. But still it could mean very very very high resistance.

What I did next gave me the biggest surprise yet.

I measured the voltage of the switch in the open/off position, without the batteries in the battery box. And to my surprise !!! It shows a voltage, 2 mV.
And the voltage did not go to zero.

No battery and yet there is a voltage ??!!?

If it's a digital meter, a low battery can cause odd readings. Also make sure the voltmeter is set to DC, not AC. An open circuit on AC will often show a stray voltage (of nearly infinitesimal current, not to worry about).

I still think there's something funny about the connections in the box. Did you try removing one battery at a time, to see if there is any combination of 3 batteries that still gives a reading?

 

[Jyera]

A very very high resistance is equivalent to an open circuit in this case, and would not allow you to measure 1.49 volts even if it were not infinite. The switch is OK.

I understand it is equivalent.
But a open circuit (infinity resistance) will not draw any current. When I switch off the battery box, there is no leakage of battery. I

That's the voltage, 2 thousands of a volt, generated either by the sweat in your socks or the fluorescent lights in your garage. Try sticking one end in your mouth and another somewhere else, and see what you read

I understand what you mean. However I have not touched any conducting part of the circuit while doing the measurement. so I cannot say my body contributed to the voltage. Placing my digital multimeter under my fluoresent light yields no readings. It simple puzzles me why a simple on-off switch without battery can provide a voltage.

Your box appears to have a short that bypasses the switch. Did you measure those paths?

Measured those paths, no short.

 

[Jyera]

If it's a digital meter, a low battery can cause odd readings. Also make sure the voltmeter is set to DC, not AC. An open circuit on AC will often show a stray voltage (of nearly infinitesimal current, not to worry about).

Measured a brand new AA battery with the multimeter and it shows 1.57V so I think it is okay. Did set the multimeter to DC mode.

I still think there's something funny about the connections in the box. Did you try removing one battery at a time, to see if there is any combination of 3 batteries that still gives a reading?

Yes. Tried that. Get the result of 0V expected of a an open circuit.

 

[Jyera]

Okay, bang goes that idea.

If it was conducting but above 2M Ohm, the voltage would be tiny, so we can be comfortable that that's not it.

The thing is that, the "Out of range" reading did not happen instantanouesly.

When I measured it, it started as 1.XXX M Ohm . And then very quick change to "out-of-range". So you could still be right that the switch behaved like a resistor when it is at off position.

Would it made a difference if the actual resistance is 1.999M Ohm. compared to if it is 2.00001 M Ohm which would make it out of range?

 

[PixyMisa]

Would it made a difference if the actual resistance is 1.999M Ohm. compared to if it is 2.00001 M Ohm which would make it out of range?

No. For our purposes, either one is close enough to an open circuit.

 

[bruto]

My next question is whether you have retested the box to see if the original fault is still there, and whether it's consistent. Perhaps there was something in the switch that has now dislodged, or changed as the switch limbered up. Have you tried putting it all back the way it was and seeing if anything is altered by wiggling the switch?

Are the connection terminals of the switch accessible? I keep thinking that if this is a new part, perhaps there's an assembly error, perhaps a crossed wire or a poorly soldered terminal or something.

Final question: where did this box come from? New or used? Is it absolutely certain that it is just a battery box and does not have any other components in it ?

 

[Jyera]

My next question is whether you have retested the box to see if the original fault is still there, and whether it's consistent. Perhaps there was something in the switch that has now dislodged, or changed as the switch limbered up. Have you tried putting it all back the way it was and seeing if anything is altered by wiggling the switch?

Have retested to be the same. Will try wiggling the switch.
But I do notice that the sliding on/off switch is not completely all the way back. But I can only push the switch back that much.

Are the connection terminals of the switch accessible? I keep thinking that if this is a new part, perhaps there's an assembly error, perhaps a crossed wire or a poorly soldered terminal or something. ?

Not very accessible.
But I'm not about to break up the switch. Even if we do break it up, we might not be able to find out what happened. [joking]After this many posts I'm beginning to think this battery box is my "golden-goose" for the JREF million. Who wants to join me to get the million? [/joking]

Final question: where did this box come from? New or used? Is it absolutely certain that it is just a battery box and does not have any other components in it ?

New, bought from a shop.
Looks remarkbly similar to this.

http://www.xleris.com/battery-holder-with-switch-cover-p-43.html
With the exception that the top "row" of plastic covering the switch and wire is not there. So I can see the wires and the switch. The switch is at the top left corner.

 

[Jyera]

Perhaps it is an assembly error.

But what kind of science would have caused such a battery box to have a voltage even when there is no battery?

 

[Elind]

I understand it is equivalent.
But a open circuit (infinity resistance) will not draw any current. When I switch off the battery box, there is no leakage of battery. I

?? You said there was "leakage". You measured 1.49v when the switch was off. There is no magic here. There is a connection through the box or you wouldn't measure it, but it doesn't seem to be the switch.

I understand what you mean. However I have not touched any conducting part of the circuit while doing the measurement. so I cannot say my body contributed to the voltage. Placing my digital multimeter under my fluoresent light yields no readings. It simple puzzles me why a simple on-off switch without battery can provide a voltage.

I was being a little humorous with my examples. You can measure milli volts in many places. Could be leakage from your house wiring if it's not all well grounded for example. Could be static if you're in a cold dry area. It could also be more mundane, in your instrument, meaning that your meter is not very accurate at that level.

Measured those paths, no short.

Yes there is and, yes you measured it, at 1.49v, remember?

Keep at it some more

 

[69dodge]

Digital voltmeters generally have high impedance, like 10 Mohms. If the resistance of the switch when "open" is 20 Mohms, one third of the battery voltage will be across the meter, so that's what it will read.

 

[Elind]

http://www.xleris.com/battery-holder-with-switch-cover-p-43.html
With the exception that the top "row" of plastic covering the switch and wire is not there. So I can see the wires and the switch. The switch is at the top left corner.

The red wire will go to the battery point on the top right corner, where the 1 is. The black will go across towards the top left corner, into one side of the switch (connection A). The other side of the switch will have a small wire connected to the top left battery terminal (connection B) (or be directly connected).

My guess is that you have a stray strand of wire or that shiny pin holding it together has damaged a wire.

First put in the batteries and make sure you still have the mystery voltage between red and black with the switch OFF, and then;

With the switch OFF, Check the resistance, without batteries, between terminal 1 and the three terminal points to the left of it. They should all be open circuit. If they are, check the same between the BLACK wire and each terminal point. They should also all be open circuit, but maybe not between BLACK and the terminal to the left of 1, which is my best guess.

Lastly, break the sucker open and look at the connections and wires closely.

 

[Elind]

Digital voltmeters generally have high impedance, like 10 Mohms. If the resistance of the switch when "open" is 20 Mohms, one third of the battery voltage will be across the meter, so that's what it will read.

In the instrument, yes, but I think he said he was able to measure down to 2 Mohms which is another order of size, and he did not see that.

 

[69dodge]

In the instrument, yes, but I think he said he was able to measure down to 2 Mohms which is another order of size, and he did not see that.

I don't understand. What did he not see?

 

[Jyera]

?? You said there was "leakage". You measured 1.49v when the switch was off. There is no magic here. There is a connection through the box or you wouldn't measure it, but it doesn't seem to be the switch.

Sorry. My fault. What I meant was that if the switch is a real open circuit(infinity resistance). It will not draw any current. And I would not be able to measure any voltage.

I was being a little humorous with my examples. You can measure milli volts in many places. Could be leakage from your house wiring if it's not all well grounded for example. Could be static if you're in a cold dry area. It could also be more mundane, in your instrument, meaning that your meter is not very accurate at that level.

Yes I know your are just being humorous. trust I do not wear sweaty socks.

Yes there is and, yes you measured it, at 1.49v, remember?
Keep at it some more

Err.... I thought a short is like short-circuit with the shorting connector at 0_ohm. So if it is a short across the switch, the reading should always maintain at 4.4V with the 4x1.1V batteries.

 

[Jyera]

Digital voltmeters generally have high impedance, like 10 Mohms. If the resistance of the switch when "open" is 20 Mohms, one third of the battery voltage will be across the meter, so that's what it will read.

My digital multimeter can only measure a Max of 2Mohm.
Is there any simple thing I can do to actually do to make it measure 20 Mohm?

 

[69dodge]

My digital multimeter can only measure a Max of 2Mohm.
Is there any simple thing I can do to actually do to make it measure 20 Mohm?

Basically, what you already did. If you measure the voltage with the switch off, and the meter reads 1/3 of the true battery voltage, that means that the resistance of the switch, when it's off, is twice the resistance of the meter.

But this is not a problem, practically speaking. If you attach some electrical device to the battery holder and slide the switch off, the device will turn off. (Unless it can run on microamps of current.)

 

[Simon Bridge]

Basically, what you already did. If you measure the voltage with the switch off, and the meter reads 1/3 of the true battery voltage, that means that the resistance of the switch, when it's off, is twice the resistance of the meter.

But this is not a problem, practically speaking. If you attach some electrical device to the battery holder and slide the switch off, the device will turn off. (Unless it can run on microamps of current.)

I concur - I suppose another way would be to measure the voltage drop when a known load is applied. This allows you to measure the internal resistance of the battery+wires+switch combination. Subtract the internal resistance of the batteries (same measurement, but the batteries need to be used outside the box) to get the resistance of the box configuration.

And, btw, this is very common - especially with slide switches. In fact, this is a good example of the difference between real and ideal components.

 

[Soapy Sam]

I nominate this thread for the...the...the jolly interesting thread award.

 

[Elind]

I don't understand. What did he not see?

I think I got that backwards. I meant he should have been able to measure the 20, but probably not. Your suggestion sounds plausible.

 

[Jyera]

I nominate this thread for the...the...the jolly interesting thread award.

Glad you enjoyed it so far.
Must give thanks to all for helping out to troubleshoot.

[joking]Only sad thing is that my "golden goose" is fading away day-by-day . I thought it would really be a jref challenge winner.[/joking]

But wait... some more to explain...

 

[Jyera]

I measured the voltage of the switch in the open/off position, without the batteries in the battery box. And to my surprise !!! It shows a voltage, 2 mV.
And the voltage did not go to zero.

No battery and yet there is a voltage ??!!?

How to explain this?

 

[bruto]

How to explain this?

Step one: replace battery in digital voltmeter and try again, because a low battery can cause this sort of error.

Step two: Crack open that battery box and check every little thing in it. It can't be that complicated. At least, on the off chance that some slightly magical combination of things has caused it to behave as if it had a capacitor in it, try briefly shorting the terminals together after removing the batteries, and try again.

Step three: call an exorcist.

 

[Elind]

Err.... I thought a short is like short-circuit with the shorting connector at 0_ohm. So if it is a short across the switch, the reading should always maintain at 4.4V with the 4x1.1V batteries.

No, as "69" (love that handle) has already explained, a very high resistance will still measure a voltage even though it will not allow a usable current (V=RA), although it is still possible that there is another short somewhere else between the batteries, as I suggested checking for.

One other simple way that occurs to check that is to put a small 1.5v flashlight bulb across the terminals when the switch is OFF. Your 1.49v should light it up, unless it is a very high resistance short, like 20 mohms in the switch.

BTW, by now your batteries must be dead. Shall we start again with new batteries and boost it up to 6v?

 

[Elind]

I nominate this thread for the...the...the jolly interesting thread award.

No, the therapy thread, in between religion and politics.

 

[Jyera]

Hi all heres the latest attempt.

Multimeter battery
Changed the battery to the digital multimeter. The old battery measured 9.1V and the new battery measured 9.3V. I left the new battery in the meter and used it for the following measurements.

Measurement with set A batteries These are the "original" batteries used above.
Individual Measurement of Voltage and Resistance all 4 AA batteries.
1.136V, 1.138V, 1.135V, 1,140V,
-0.778Ohm, -0.778Ohm, -0.777Ohm, -0.778Ohm.

When the batteries are placed in the battery box, and
voltage across the output is mesaured.
Switch @ "on" : 4.54V
Switch @ off : 2.26V (this is inconsistent also measured 1.82V, 2.4V)

Measurement with set B batteries
Individual Measurement of Voltage and Resistance all 4 AA batteries.
1.044V, 1.041V, 1.042V, 1,042V,
-0.771Ohm, -0.771Ohm, -0.771Ohm, -0.771Ohm.

When the batteries are placed in the battery box, and
voltage across the output is mesaured.
Switch @ "on" : 4.16V
Switch @ off : 2.23V

Resistance were measured by setting the Digital Multimeter to 2M Ohm range, and placed the black/red at the positive/negative terminal of the battery respectively.