Where is this voltage coming from?

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Mark Nunn
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Where is this voltage coming from?

Post by Mark Nunn » Tue Oct 04, 2022 1:55 pm

I am confused. My generator recently stopped working and I need to review the service and electrical manuals for that. I wanted to check continuity through the cutout with the engine off. There was none. I have a new analog multimeter that I wanted to try so I checked battery voltage. 6.02V I checked voltage at the yellow (battery) wire on the generator. To my surprise, I had 3.3 volts. I was surprised because my battery disconnect switch was in the OFF position. The switch is wired on the ground strap.

I disconnected the positive cable at the battery and checked voltage from the negative post and body ground. I got 3.3 volts. The battery disconnect was still in the off position with the positive cable disconnected. Where is the voltage coming from? I don't have another battery anywhere. Could the potential be coming from coil capacitors? That is the only source I can think of. I want to get this sorted before I start messing with the generator. I plan to start disconnecting wires starting at the battery negative and disconnect switch.
3 volts.jpg


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Re: Where is this voltage coming from?

Post by TXGOAT2 » Tue Oct 04, 2022 2:24 pm

Coil capacitors would discharge very quickly through the voltmeter, if they hadn't already "leaked off". There should be no continuity through the cutout with the generator not turning at a good rate. The wire from the cutout to the vehicle should show battery voltage with the battery connected. As for the stray voltage, I know of no other devices on a stock T that would retain a charge, other than the coil capacitors. It may be that your disconnect switch is leaking some current due to moisture or residue collecting inside it. The crud that can collect on top of batteries is usually acidic, and can conduct current under some conditions. If you are using a senstive voltmeter, even a little crud on the terminal insulator area of the disconnect switch might leak a little current. From the - battery post to ground should read 0 or very close to it, even if the starter is engaged. From the + battery post to ground should read the same as from one post to the other. The disconnect switch should show 0 ohms when closed, and infinity when open.
As for the generator, you might connect something like a 6 volt headlight bulb to the terminal on the generator case and a good ground and start the motor and let it idle. The bulb should light up. The dash ammeter should show 0 ohms between the terminals, and infinity between either terminal and the body of the ammeter.


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Re: Where is this voltage coming from?

Post by Scott_Conger » Tue Oct 04, 2022 2:26 pm

1. FWIW, 6.02V is pretty much a dead battery
2. Disconnect on (-) is in my opinion, the wrong post
3. Disconnect very likely has a high resistance short which is allowing some voltage to the "battery" wire on the disconnect...it won't conduct amperage but will allow voltage to show up...if this is the case, then "connected" irregularities may also be occurring (see 5. below)
4. Regardless of their saftey/utility in installation, any disconnect other than a knife-switch is going to fail "open" eventually
5. With what you are finding, there is at least some possibility that your disconnect caused generator issues
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Re: Where is this voltage coming from?

Post by TRDxB2 » Tue Oct 04, 2022 2:32 pm

Based on your description there would be no connection of the negative terminal on the battery to the body ground with the disconnect off. If the disconnect was connected you would be testing a ground to ground connection for continuity and not in either a series or parallel circuit to a voltage.
But you may be measuring the difference between the battery ground and earth ground. Make sure the positive cable is not touching
Explanation from the Internet
https://www.learningaboutelectronics.co ... ltage.html
"If a battery has negative orientation, its voltage with respect to ground is more negative than ground, and it delivers positive current to the ground part of a circuit."
--
https://maker.pro/forums/threads/differ ... ge.277846/
-Ve is a voltage negative with respect to ground. Ground or 0V is typically the reference potential within a circuit. When you connect the "+" pole of a battery to gnd, then the "-" pole of the battery is negative with respect to ground
--
Make sure the positive cable end is not touching any part of the car, ie insulated when you do your tests
Curious: If you reverse the test leads do you get a different reading?
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Re: Where is this voltage coming from?

Post by Mark Nunn » Tue Oct 04, 2022 3:43 pm

TRDxB2 wrote:
Tue Oct 04, 2022 2:32 pm

--
Make sure the positive cable end is not touching any part of the car, ie insulated when you do your tests
Curious: If you reverse the test leads do you get a different reading?
My positive was not insulated during tests. When I reversed the leads from the photo the voltage went negative. I had the same result using a digital meter. The 3.3 volts went to zero when I turned the disconnect to on.

"2. Disconnect on (-) is in my opinion, the wrong post" I know but it was so convenient.

"3. Disconnect very likely has a high resistance short which is allowing some voltage to the "battery" wire on the disconnect...it won't conduct amperage but will allow voltage to show up...if this is the case, then "connected" irregularities may also be occurring" I immediately suspected the disconnect.

There is one other thing I did not mention originally. I checked continuity from the generator post to a screw holding the cutout onto the gen case. There was 0 ohms. Shouldn't that be an open loop?


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Re: Where is this voltage coming from?

Post by Art M » Tue Oct 04, 2022 3:53 pm

Zero ohm is what it should be

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Re: Where is this voltage coming from?

Post by Mark Nunn » Tue Oct 04, 2022 4:51 pm

I disconnected and insulated both cables from the battery and I still get 3.3 volts from the negative battery post to body ground. I have a leak somewhere in or around the battery that needs to be eliminated. I will start by removing the battery and cleaning everything up before doing anything else. Thank you for the assistance.


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Re: Where is this voltage coming from?

Post by Scott_Conger » Tue Oct 04, 2022 5:08 pm

Mark

let me ask or suggest that you are reading perhaps 3.3mV?

I'm not sure that meter could even be set to that range, much less believe it, but something does not add up at all
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Re: Where is this voltage coming from?

Post by TWrenn » Tue Oct 04, 2022 5:41 pm

Gosh golly gee, I LOVE my alternator!! :lol:

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Re: Where is this voltage coming from?

Post by TRDxB2 » Tue Oct 04, 2022 5:47 pm

What type of battery disconnect do you have and where is it located? I couldn't tell in the photo.
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Re: Where is this voltage coming from?

Post by Mark Nunn » Tue Oct 04, 2022 5:54 pm

Scott,

You had me doubting my meter settings so I rechecked. My digital meter was set to 20V full scale and analog set to 10V full scale. I think Pat is correct that there is a lot of crud on the battery that can conduct electricity. I also have a wood block under the battery and one on the side to stabilize it. Wet wood can also drain a battery.

Tim,

I am among the anti-alternator crowd but have considered getting one recently. I put one on my '41 tractor and loved it. I have too many tests to conduct before letting my generator go without a fight.

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Re: Where is this voltage coming from?

Post by Mark Nunn » Tue Oct 04, 2022 5:57 pm

TRDxB2 wrote:
Tue Oct 04, 2022 5:47 pm
What type of battery disconnect do you have and where is it located? I couldn't tell in the photo.
I have one of the master disconnect switches sold by the vendors in the trunk floor.


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Re: Where is this voltage coming from?

Post by Mike Fortney » Tue Oct 04, 2022 6:38 pm

Your voltage may be coming from the contamination across the top of the battery


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Re: Where is this voltage coming from?

Post by Allan » Tue Oct 04, 2022 7:45 pm

If the smoke is still in the wires, you have nothing to worry about.

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Re: Where is this voltage coming from?

Post by TWrenn » Tue Oct 04, 2022 7:48 pm

Mark Nunn wrote:
Tue Oct 04, 2022 5:54 pm
Scott,

You had me doubting my meter settings so I rechecked. My digital meter was set to 20V full scale and analog set to 10V full scale. I think Pat is correct that there is a lot of crud on the battery that can conduct electricity. I also have a wood block under the battery and one on the side to stabilize it. Wet wood can also drain a battery.

Tim,

I am among the anti-alternator crowd but have considered getting one recently. I put one on my '41 tractor and loved it. I have too many tests to conduct before letting my generator go without a fight.
Mark, no problem, no judging, as I don't wanna be judged either. I just like to "remind" folks how happy I am with finally making the switch. I too went a long time with a lot, and I mean a LOT of fighting with the generator! :lol:


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Re: Where is this voltage coming from?

Post by Scott_Conger » Tue Oct 04, 2022 8:02 pm

Regardless of where you fall on the generator/alternator issue, I am continually perplexed at the idea of "wrestling with the generator", giving up, and then spending the same amount of money for an alternator that could otherwise have bought a remanufactured generator which would go another 80 years.

For some reason, the generator is the only part of a T for which a Band-Aid is an accepted substitute for repair, and the owner all too often steadfastly refuses professional help up to and including the day that they junk the poor thing.

It's this odd stubbornness that put me out of the generator business early enough in my path through the hobby to find another vocation in the manufacture of carb parts. So, in the end, we're all happy - generator, alternator, whatever.

no Band-Aids here
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P9190028.JPG
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Re: Where is this voltage coming from?

Post by mtntee20 » Tue Oct 04, 2022 8:13 pm

Mark,

Do you live near any transmission towers? TV, Radio, Micro wave communication, Overhead high voltage power lines, and/or Cell phone ground station?

Years ago, the Disney channel had a TV transmission tower near a waste water treatment plant we often were called to work at. Having a crane boom in the air near that tower, we had to put a nylon strap between the hook and whatever we were hoisting. Being a crane operator, we had to be aware of transmission towers. I could lay a steel choker end on the ground and take the other end, rub it on the hook and see sparks jumping from the hook to the choker to ground. I know transmission towers are NOT supposed to do that but this one did and so did some others we worked near.

Maybe you measuring power from an outside source?

Good Luck
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Re: Where is this voltage coming from?

Post by TRDxB2 » Tue Oct 04, 2022 8:22 pm

TWrenn wrote:
Tue Oct 04, 2022 7:48 pm

Mark, no problem, no judging, as I don't wanna be judged either. I just like to "remind" folks how happy I am with finally making the switch. I too went a long time with a lot, and I mean a LOT of fighting with the generator! :lol:
This discussion isn't about the generator but the battery showing a voltage. The same issues could have evolved with an alternator not working.
Here's a link where a member had the same issues with a generator and then again converting to an alternator.
viewtopic.php?t=30909

Can you provide any ideas that might resolve the voltage issue when the engine is not running?
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Re: Where is this voltage coming from?

Post by TXGOAT2 » Tue Oct 04, 2022 9:01 pm

There is a major power line about 15 miles from here. You can park off the road directly under it. I parked my T there a few weeks ago, and noticed that when I got out and stood on the dry, gravelly ground and touched the car, it felt like the car was vibrating. This car has thick black paint on it. No bare metal. If I put both hands on the car, the effect vanished. I drove 5 miles down the road to another stop and got out and checked for the effect. Nothing. I suspect that if the ground was damp and I was wearing wet shoes, touching the car would give a shock.

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Re: Where is this voltage coming from?

Post by JTT3 » Tue Oct 04, 2022 9:21 pm

Mark just for giggles can you take the master disconnect switch out of the loop. About 13 years ago I was having some issue similar to yours and talked to 2 folks that were/are major vendors for products involving the electrical system for model T’s. Both told me the same thing about the master disconnect & suggested I remove it. I did & problem solved. This may or may not be the answer for you but easy to rule it out. This falls in line with what Scott posted earlier.


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Re: Where is this voltage coming from?

Post by Scott_Conger » Tue Oct 04, 2022 9:25 pm

I, too, have gotten out of my car and felt it vibrating, and I was nowhere near a powerline
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Re: Where is this voltage coming from?

Post by TXGOAT2 » Tue Oct 04, 2022 9:34 pm

If you were in Oklahoma, it was probably the continous earthquakes caused by the frackers.

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Re: Where is this voltage coming from?

Post by Flivver » Wed Oct 05, 2022 2:23 am

Fascinating. Subscribed.

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Re: Where is this voltage coming from?

Post by Mark Nunn » Wed Oct 05, 2022 8:50 am

John T,

I disconnected both battery cables which should eliminate all passageways through the switch. With the battery still in its carrier, I get the same 3.3V from the negative battery post and body ground. There are no electrical or transmission towers within miles of my house to offer interference. I will get time Thursday to clean everything up and retest.


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Re: Where is this voltage coming from?

Post by Jim Sims » Wed Oct 05, 2022 9:00 am

Try a different volt meter. what you are describing sounds impossible.


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Re: Where is this voltage coming from?

Post by Moxie26 » Wed Oct 05, 2022 9:35 am

Jim Sims wrote:
Wed Oct 05, 2022 9:00 am
Try a different volt meter. what you are describing sounds impossible.
. I certainly agree with Jim...

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Re: Where is this voltage coming from?

Post by JTT3 » Wed Oct 05, 2022 9:53 am

Ok spit balling here, do you have an aluminum head? To the folks more electrically inclined, if he has an aluminum head could electrolysis give a reading? May be far fetched I know but other than a need to use a different analog meter what could explain the impossible.


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Re: Where is this voltage coming from?

Post by mtntee20 » Wed Oct 05, 2022 10:19 am

Well, we're eliminating possibilities.

I suggest removing the battery from the car. Place it on the ground near enough for your test leads to reach both the battery and car. Test again.

There has to be a complete circuit for current to flow and voltage to be measured. The battery has to be connected to the car in some way, even with the cables removed. As was suggested above, the battery acid/corrosion build ups on the top, sides, and bottom, are able to conduct electricity. My guess is, a good cleaning of the battery exterior and battery holder will eliminate the problem.

And, yes, galvanic corrosion between an aluminum head and iron block will show measurable current. It will be a short circuit between the aluminum and iron through the coolant. Thus the need for a sacrificial anode that will be corroded away instead of the head (being the softer metal). This process normally does NOT include the car battery in the circuit.


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Re: Where is this voltage coming from?

Post by Scott_Conger » Wed Oct 05, 2022 10:57 am

I suspect that the government will soon be sending someone to Marks house to confiscate this source-less supply of electricity and store it away next to the Holy Grail, never to be seen or studied ever again.

Mark - don't answer the door!
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Re: Where is this voltage coming from?

Post by TXGOAT2 » Wed Oct 05, 2022 11:19 am

I suspect acid residue on the battery case, or possibly a hairline crack or pinhole leak in the battery case.

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Re: Where is this voltage coming from?

Post by Mark Nunn » Wed Oct 05, 2022 11:23 am

Jim Sims and Robert,
I used an analog meter and a different digital meter with the same result.

John T,
Iron head.

Scott,
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Re: Where is this voltage coming from?

Post by TXGOAT2 » Wed Oct 05, 2022 11:24 am

If your car is creating energy, perhaps as a result of a mysterious alien encounter, do not tell anyone, unless you want to be locked away in the secret cell in the Canadian North Woods with Dr. Pogue and Jimmy Hoffa and Joe Camel.

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Re: Where is this voltage coming from?

Post by JTT3 » Wed Oct 05, 2022 12:17 pm

To paraphrase the PATERFAMILIAS of “Oh brother where art thou”
Ain’t this a electrical oddity 3.3 volts from everywhere


“I want to believe, the truth is out there somewhere”


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Re: Where is this voltage coming from?

Post by Scott_Conger » Wed Oct 05, 2022 1:32 pm

3.3VDC is a common voltage used in computers and as a result, many chargers and accessories...what else is hooked to the car?
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Re: Where is this voltage coming from?

Post by Mark Nunn » Wed Oct 05, 2022 1:36 pm

Scott_Conger wrote:
Wed Oct 05, 2022 1:32 pm
..what else is hooked to the car?
I have a board propping up the trunk lid. Nothing else is attached.

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Re: Where is this voltage coming from?

Post by Mark Gregush » Wed Oct 05, 2022 1:52 pm

Do you have something like a GPS installed and hooked up to the system through a charging port that could be giving its battery reading?
I know the voices aren't real but damn they have some good ideas! :shock:

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Re: Where is this voltage coming from?

Post by Mark Nunn » Wed Oct 05, 2022 2:03 pm

No, Mark. The only electrical add-ons are a second taillight, brake light switch and turn signal kit. I think it's a dirty battery. I am up to my eyeballs with work right now and finding barn-time is difficult. I will miss our club outing on Sunday unless something miraculous happens.

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Re: Where is this voltage coming from?

Post by MKossor » Wed Oct 05, 2022 5:12 pm

Something must be completing the circuit between "Open" positive battery terminal and chassis ground in order for you to be reading 3.3 Volts across the open battery disconnect switch using your analog voltmeter. A typical analog meter has in internal resistance of approximately 20K Ohms/V so on the 20 V scale would be about 400K Ohms. The voltage you measure is approximately half the battery voltage (3.3V) so that would mean the mystery leakage resistance between the "open" positive battery terminal and frame ground would be approximately the same resistance as the analog meter internal resistance (400K Ohms) in order to drop about half the voltage. That just seems exceptionally low resistance for dirt/film residue on the battery case visible in the photo. Cleaning the top surface of the battery around the positive battery terminal should eliminate that leakage residue theory from further consideration. Removing the battery from the car and repeating the voltage measurement across the disconnect switch would also be of interest. If the 3.3V reading still prevails, I suspect something else going on here (meter set to AC volts, Ohms, DC mV, frequency, capacitance, etc) may be skewing a logical conclusion.
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Re: Where is this voltage coming from?

Post by TXGOAT2 » Wed Oct 05, 2022 5:19 pm

If the battery residue is very dry, it can have a high resistance. Some road dust is fairly alkaline, and if the residue had a good deal of such dust in it, That might also increase the resistance.


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Re: Where is this voltage coming from?

Post by J1MGOLDEN » Wed Oct 05, 2022 7:21 pm

Junk that meter and get an earlier type with a needle display, commonly called an analog meter or multimeter if it measure both AC and DC and Ohms or Resistance.

The transistors are too sensitive to the AC voltage especially from the spark plug leads when the engine is running.

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Re: Where is this voltage coming from?

Post by Mark Gregush » Wed Oct 05, 2022 9:01 pm

J1MGOLDEN wrote:
Wed Oct 05, 2022 7:21 pm
Junk that meter and get an earlier type with a needle display, commonly called an analog meter or multimeter if it measure both AC and DC and Ohms or Resistance.

The transistors are too sensitive to the AC voltage especially from the spark plug leads when the engine is running.
Go back and look the very first photo, he is using an analog meter.
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Re: Where is this voltage coming from?

Post by Novice » Wed Oct 05, 2022 10:22 pm

If you tightly grasp both meter leads while the meter is showing the 3 volts You will probably see the voltage drop or disappear. Modern meters are very sensitive and will pick up even the slightest leaking but with any load ever so slight such as your body resistance the voltage will go away. Like was said clean up the battery top and bottom and don't worry about the slight leakage if its still there. My bet is It wont be. Good Luck. I take it this generator has been working ? some take a while to start generating enough power to close the cut out. The one on my T can take up to several minutes before it starts putting out amps.

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Re: Where is this voltage coming from?

Post by Mark Nunn » Thu Oct 06, 2022 7:36 am

My generator has been working fine since I rebuilt it 3 years ago. I'm hopeful that eliminating the voltage leak and re-flashing the generator will get me back on the road.

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Re: Where is this voltage coming from?

Post by Mark Nunn » Thu Oct 06, 2022 8:23 am

I moved my battery clamps out of the way and my free electricity is gone. Time for cleaning.
PXL_20221006_121942893.jpg
There is Galvanic corrosion on screws of my riser block too.
PXL_20221006_122712339.jpg
Last edited by Mark Nunn on Thu Oct 06, 2022 8:53 am, edited 1 time in total.


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Re: Where is this voltage coming from?

Post by speedytinc » Thu Oct 06, 2022 8:24 am

Filthy battery!

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Re: Where is this voltage coming from?

Post by Charlie B in N.J. » Thu Oct 06, 2022 8:46 am

Batt has created it’s own circuit. Usually through dampness. A good cleaning and replace wood with non conductive materials.
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Re: Where is this voltage coming from?

Post by TXGOAT2 » Thu Oct 06, 2022 9:34 am

Batteries need to be kept clean and dry. Your battery may be suffering from poor charging circuit regulation, which is a trait of the Model T system. Overcharging will increase the tendency of the battery fluid to escape the cells as vapor and mist and cause corrosion and filth to accumulate. Checking the battery fluid level regularly very important. Add only distilled water, if needed, and do not overfill. Batteries age and decay, even under the best of conditions. If your battery is 3 years old or older, it is probably just about junk, especially if it is a cheap battery to begin with. There are things you can do when running a Model T to manage the battery charging rate which are discussed at length elsewhere on this site, and doing these things will enhance battery life and prevent problems with the battery, starter, and generator. The Model T system depends on a good battery in good condition to work as it should, with the charging rate adjusted to the best advantage for operating conditions. Cleaning the battery and the area around it regularly will prevent problems with the battery and cables and prevent acid residue from damaging the car's body and frame and battery carrier. A battery with residue on it can self-discharge due to leakage of current through the residue. Buying a good quality battery is always a good investment.

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Re: Where is this voltage coming from?

Post by TRDxB2 » Thu Oct 06, 2022 10:49 am

Mark Nunn wrote:
Tue Oct 04, 2022 5:57 pm
I have one of the master disconnect switches sold by the vendors in the trunk floor.
While your cleaning the battery and cable connections you should also clean the master disconnect switch terminals.
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Re: Where is this voltage coming from?

Post by Scott_Conger » Thu Oct 06, 2022 10:55 am

It's the internal contacts which will fail, not so much the terminals, though I agree it is always good practice to clean all connections.
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Re: Where is this voltage coming from?

Post by Mark Nunn » Fri Oct 07, 2022 12:33 pm

I washed the battery, carrier and wood blocks. I had some EPDM (rubber) membrane material that I stuck to the wood as an insulation. I put a layer on the bottom of the wood too for extra isolation between the battery and carrier. I got some voltage leak. I wrapped that battery in EPDM for another layer.

Guess what, there is still a voltage from the negative post and ground.
PXL_20221006_195419655.jpg
PXL_20221006_155016800.jpg
PXL_20221006_155911501.jpg
I removed the hold-down clamps and voltage went to 0. I could press down on the battery with my hand and produce some voltage. This is so bizarre. I'm going out now for more tests with a third digital meter. The EPDM tested as an open loop on the ohmmeter.


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Re: Where is this voltage coming from?

Post by TXGOAT2 » Fri Oct 07, 2022 12:48 pm

It seems some voltage may somehow be leaking from the battery + post or inside the battery to ground when the battery is in the car. That should not happen with a clean, dry battery. A hairline crack or pinhole in the battery case could allow that. I don't know what else would cause it with a clean battery. You do have dissimilar metals in the ground cable, including lead, copper, perhaps brass, and steel. A poor connection in this circuit could allow for some weak galvanic action that might account for a very low reading. *** If you test directly from the battery negative post to a bright, clean spot on the frame, with the positive battery post disconnected, do you get a reading? You should not. Doing that test should eliminate everything but the battery itself, unless you are measuring a voltage induced from house wiring, which is very unlikely.


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Re: Where is this voltage coming from?

Post by Moxie26 » Fri Oct 07, 2022 1:07 pm

Get yourself a new battery, and then do the same tests and see if you have the same result. ..... Analog meters give better results than digital meters in my opinion.

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Re: Where is this voltage coming from?

Post by Mark Nunn » Fri Oct 07, 2022 3:50 pm

TXGOAT2 wrote:
Fri Oct 07, 2022 12:48 pm
. *** If you test directly from the battery negative post to a bright, clean spot on the frame, with the positive battery post disconnected, do you get a reading? You should not. Doing that test should eliminate everything but the battery itself, unless you are measuring a voltage induced from house wiring, which is very unlikely.
Pat, there was no voltage between a good ground and negative post with everything disconnected. I turned off the power to the barn to eliminate outside sources.

I've had the battery on a charger/maintainer for 20 hours. I'm up to 6.48V and the charger has not switched to maintain yet. I,too, suspect the battery.


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Re: Where is this voltage coming from?

Post by Moxie26 » Wed Oct 12, 2022 7:35 pm

Mark, any updates on your problem ????

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Re: Where is this voltage coming from?

Post by Mark Nunn » Thu Oct 13, 2022 8:52 am

Robert, in my posted photo above you can see 2.82V with the battery clamped in place. I did not mention his but before putting the clamp on the battery I was able to vary the voltage by pressing on the top of the battery case near the positive post. 2.82 was the max. That just adds to the list of questions.

I had to stop working on this for now. I am currently putting up a building to house my camper and that is taking all of my spare time.

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