Magic DC

[bill good]

& what happens when you disconnect the battery charger with only the + batt term connected??

[sailorboy1]

So, so far we have suggested:

1 - It doesn't matter that the battery (-) isn't connected current still flows because there is a "potential"

2 - The current is jumping out of the disconnected (-) cable and flowing up the battery case to the terminal to complete the circuit

I'm not really accepting either of these. The facts still remain that the (-) cables were disconnectet so how could a circuit to the battery be completed? If the answer is that the circuit is getting completed via the AC ground system wouldn't that mean the batteries would always discharge through it?

[NahanniV]

Originally Posted by sailorboy1

So, so far we have suggested:

1 - It doesn't matter that the battery (-) isn't connected current still flows because there is a "potential"
....

Just to reiterate what has already been said:
#1 is FALSE.
The potential generated by a battery is between it's TWO posts ONLY.
Current in the negative side will always equal the positive side of the same battery.

Originally Posted by boatpoker

...noticed recently that all of what we think of as known science in electrical matters is still noted as "theory" in serious scientific journals.

Every scientific explanation is a theory; The theories relevant to this problem have stood for hundreds of years; I doubt very much that any theories will need to be altered when the cause of this problem is discovered.

Suggestions:
1/Stop thinking MAGIC !
2/Measure the current
3/Measure the voltage across the device.

Cheers,
JM.

[skipmac]

Originally Posted by Paul Elliott

No.

If the battery negative terminal is unconnected then there is no positive potential anywhere. A battery with a floating (-) terminal has absolutely no effect on the rest of the circuit.

OK. I had to think about this again. I extrapolated from other non-complete circuit situations like static electricity. Shuffle across a carpet, build up a charge on your body and touch a doorknob. There is a definite potential and flow of current but there is no complete circuit from one origin and back, + and - poles, etc. so I reasoned the same thing could happen with a battery.

So, grabbed a couple of batteries and a meter and tested it. I set two 9V alkalines side by side but not touching and put the meter leads between the + of one and the - of the other and I did read a voltage. It was tiny fractions of a volt but definitely there. Tried the same thing with one battery and the AC ground in an outlet and got the same results.

This may not be the cause of Sailorboy's problem but there is a measurable potential difference from an isolated battery terminal to some outside point.

[unclemack]

BMV 600 was nearest I found. Runs on as little as 1ma apparently.

Touching the negative battery terminal with just your finger might start such a sensitive meter.

Set a multimeter to around 40V DC, hold neg. probe between your fingers and touch nothing else with your body.
Touch pos. meter probe to 12V battery pos.
I read 6V on mine with dry fingers.
On a low enough setting the meter will respond without actual contact, just proximity.

[Tingum]

I will second a very low capacity ground through the bonding system. Most instruments just need millivolts to get a reading.

[NahanniV]

Originally Posted by skipmac

OK. I had to think about this again. I extrapolated from other non-complete circuit situations like static electricity. Shuffle across a carpet, build up a charge on your body and touch a doorknob. There is a definite potential and flow of current but there is no complete circuit from one origin and back, + and - poles, etc. so I reasoned the same thing could happen with a battery.

So, grabbed a couple of batteries and a meter and tested it. I set two 9V alkalines side by side but not touching and put the meter leads between the + of one and the - of the other and I did read a voltage. It was tiny fractions of a volt but definitely there. Tried the same thing with one battery and the AC ground in an outlet and got the same results.

This may not be the cause of Sailorboy's problem but there is a measurable potential difference from an isolated battery terminal to some outside point.

Static electricity would not keep the device operating, unlikely that it would even light the display.

For the device to turn on and remain on there needs to be current flowing.

In your example with the two batteries, set up your meter to read current; There will no measurable sustained current until there is a circuit.

Cheers,
JM.

[sailorboy1]

I think there is a big difference between a potential and actual current flow.

[sailorboy1]

Originally Posted by skipmac

OK. I had to think about this again. I extrapolated from other non-complete circuit situations like static electricity. Shuffle across a carpet, build up a charge on your body and touch a doorknob. There is a definite potential and flow of current but there is no complete circuit from one origin and back, + and - poles, etc. so I reasoned the same thing could happen with a battery.

So, grabbed a couple of batteries and a meter and tested it. I set two 9V alkalines side by side but not touching and put the meter leads between the + of one and the - of the other and I did read a voltage. It was tiny fractions of a volt but definitely there. Tried the same thing with one battery and the AC ground in an outlet and got the same results.

This may not be the cause of Sailorboy's problem but there is a measurable potential difference from an isolated battery terminal to some outside point.

But if you remove the connection to the (-) what happens?

[NahanniV]

Originally Posted by unclemack

BMV 600 was nearest I found. Runs on as little as 1ma apparently.

Touching the negative battery terminal with just your finger might start such a sensitive meter.

Set a multimeter to around 40V DC, hold neg. probe between your fingers and touch nothing else with your body.
Touch pos. meter probe to 12V battery pos.
I read 6V on mine with dry fingers.
On a low enough setting the meter will respond without actual contact, just proximity.

According to the manual BMV600 needs 4mA @ 12v :
https://www.victronenergy.com/upload...S-SE-IT-PT.pdf

Try your finger experiments while measuring current to see if there is any real potential.

Cheers,
JM.

[sailorboy1]

I have thought of one possible source:

I have a small solar panel that supplies the start battery. It could be possible that there could be some leakage across the isolator into the house system and a circuit could be completed via the solar panel itself.

[unclemack]

@ sailorboy

Curious to know how it's possible that you haven't yet solved this yourself?

You seem happy to deny the possibility of anyone else's suggestions being relevant.

Odd when the clues you've provided are almost non-existent.

Victron doesn't state whether its device's memory is non-volatile and I saw no indication of its production years - but it does appear to have been superseded.

Many early devices had memory caps and timed shut down reset by a single pulse.

My last.

[skipmac]

Originally Posted by NahanniV

Static electricity would not keep the device operating, unlikely that it would even light the display.

For the device to turn on and remain on there needs to be current flowing.

In your example with the two batteries, set up your meter to read current; There will no measurable sustained current until there is a circuit.

Cheers,
JM.

Agree, I never claimed that static electricity would operate any device, just using it as an example of potential and current without a closed, complete circuit. Of course static wouldn't keep a device operating but it could certainly fry the ICs in it.

I did say in my previous post that the voltage measured would not (I think I included a probably) activate the device but there was a definite potential measured IE more than none or zero as has been claimed.

And I did test for current. My good Fluke meter is on the boat so used the cheapo spare. Got a very brief blip of the - polarity LCD but no digits. Might have been a very small, short lived current as in micro amps but nothing significant.

For similar reasons (a very small potential difference at best) I think the idea that the monitor activates due to a circuit from the battery + to the - terminal completing through contamination on the battery case would be unlikely. The contamination would have to be extreme.

[skipmac]

Originally Posted by sailorboy1

But if you remove the connection to the (-) what happens?

Still got a reading. Smaller 0.2 mV but still showed a voltage potential.

Here's another question (or two). Don't you have an always on circuit directly to the battery and bypassing the panel for a bilge pump? Is that connected when you see the monitor come on?

What about the battery charger? Is that operating when this happens?

[sailorboy1]

Originally Posted by unclemack

@ sailorboy

Curious to know how it's possible that you haven't yet solved this yourself?

You seem happy to deny the possibility of anyone else's suggestions being relevant.

Odd when the clues you've provided are almost non-existent.

Victron doesn't state whether its device's memory is non-volatile and I saw no indication of its production years - but it does appear to have been superseded.

Many early devices had memory caps and timed shut down reset by a single pulse.

My last.

WTF, you go onto the "special" list