Explain battery voltage?

[KY Gun Geek]

Not a tear in space-time, but the quantum behavior of a semi-conductor.

I think you are seeing forward bias voltages on a diode(s) somewhere. The are not linear, but rather constant, typically in the .5 to .7 range, and are seen with very small current . You will see the drop with very small amounts of current flowing. Standard demo in electronics class from long ago.

Diodes - learn.sparkfun.com

 

[CobyRupert]

But you are bridging that open circuit with the meter. Similar to you bridging the open circuit between the posts with the meter.

Yes.
I bridge open circuit between battery posts and get 12.6V
I bridge open circuit between disconnected battery neg(-) post and disconnected neg(-) cable and get 11.7V.
(Same as across the OPEN disconnect switch when I connected into the neg(-) cable and battery.)

 

[jaydee325]

A volt meter only measures voltage potential. An ammeter measures current flow. If you wire an appropriate ammeter between the negative cable and battery post, you will read the current flow in amps from your circuit leak.

 

[EarPlug]

But you are bridging that open circuit with the meter. Similar to you bridging the open circuit between the posts with the meter.

To clarify, by bridging, what you are actually doing is completing the circuit across the open switch. You cannot measure the voltage across the open switch. If you measure across you need to be measuring Current/AMPS.

If you want to measure the voltage drop of the system, place your voltage meter on the battery terminals. Then measure the battery voltage with the disconnect switch open and then closed.

To be able to find the device that is drawing power when the key is off you want to measure the current across the open switch. If something is drawing current (i.e. draining the battery) you will measure some amount of AMPS. If you get a reading then just start disconnecting thing until the current reading is Zero.

The Battery supplies Voltage - Devices consume Current.

 

[CobyRupert]

Yes.
I bridge open circuit between battery posts and get 12.6V
I bridge open circuit between disconnected battery neg(-) post and disconnected neg(-) cable and get 11.7V.
(Same as across the OPEN disconnect switch when I connected into the neg(-) cable and battery.)

I misused the term “bridge” to mean measured.

I know what the leakage current is when an ammeter completes the loop from the battery’s positive post to the negative post through the atv’s leak. It’s:
30mA (30 milliamperes, .03 of an amp)

When I disconnect the negative cable from the negative post, leakage current should be: 0 amps (Zero) (but we have no way to directly measure. We can only observe it is disconnected.)

We can only measure the voltage. Which suggests there’s current flowing (and a voltage drop occurring).
But this suggests the current is flowing through the volt meter when you complete the circuit.
But this suggests meter is very low resistance.
...or as was mentioned, it could be diodes.

Ahh, now I get it. The 30mA leakage is a moot point, insignificant when measuring the open cable voltage to battery post.

That reading is a simple voltage divider across ATV circuits and meter. Doesn’t mean meter is low resistance. It’s the ratio of those resistances.
Something like 11.7v/12.6v= Rmeter/(Rmeter+Ratv)
Solve for ratio that gives 11.7 volts across cable and terminal when battery is 12.6V.

 

[Industrial Toys]

Maybe the second black hole discovered.

It might be easier to understand by taking some measurements of a good system. Then maybe add a resisor to ground somewhere and see what kind of readings you get.

In many instances over the years, I don't like using a Digital meter. One electrician was dumb founded that he still had "Voltage" on disconnected conductors. I had to explain to him that the voltage was being induced into those conductors by other conductors present in the same conduit drawing current. He never would have seen that voltage with an analogue meter.

Anyway, thats AC, Different ball game, but just speaking of meters.

 

[vvanders]

Not a tear in space-time, but the quantum behavior of a semi-conductor.

I think you are seeing forward bias voltages on a diode(s) somewhere. The are not linear, but rather constant, typically in the .5 to .7 range, and are seen with very small current . You will see the drop with very small amounts of current flowing. Standard demo in electronics class from long ago.

Diodes - learn.sparkfun.com

Yup, sounds like diode voltage drop or reverse biased FET. Not really a big deal and pretty normal.

 

[Industrial Toys]

It is a big deal if it discharges your battery in an untimely manner. Anything, should be able to sit at least a few months with a healthy battery and still start.

 

[Doofy]

Added a master disconnect to my Ford Ranger on the negative side also due to a parasitic draw. New battery will still go dead in a little over a month of sitting. No clue why this is still happening.

 

[CobyRupert]

Added a master disconnect to my Ford Ranger on the negative side also due to a parasitic draw. New battery will still go dead in a little over a month of sitting. No clue why this is still happening.

Is the "battery side" of the master disconnect switch somehow touching the frame? That is, is the leakage current bypassing the open switch by using the frame?

I've "heard" (take w/ grain of salt) that batteries can discharge by using the dust on their cover as a path. That's hard to believe, but the smallest of current when given enough time is equivalent (energy) to any other amount of current.