The Ford Barn

jwaldrich · 02-22-2020, 12:08 PM

On a 6 volt positive ground flat head V8, and if everything is working correctly, can I remove the negative cable from the battery while the car is running and expect the car to continue to run on the generator?

Kurt in NJ · 02-22-2020, 01:51 PM

it depends ----on a 3 brush with cutout at idle --no , ig engine running fast enough to charge and battery cable removed the voltage can go over 40 volts and if kept that way long enough smoke starts to come out of wires, points,coil can burn up, and any light bulbs that are on will burn out ----ending when the fried generator finishes itself off

on a 2 brush with regulator that engine is running fast enough to be charging it will keep running, but it won't like it and the regulator has to work overtime to keep control ---

jwaldrich · 02-22-2020, 02:00 PM

Quote:

Originally Posted by Kurt in NJ

it depends ----on a 3 brush with cutout at idle --no , ig engine running fast enough to charge and battery cable removed the voltage can go over 40 volts and if kept that way long enough smoke starts to come out of wires, points,coil can burn up, and any light bulbs that are on will burn out ----ending when the fried generator finishes itself off

on a 2 brush with regulator that engine is running fast enough to be charging it will keep running, but it won't like it and the regulator has to work overtime to keep control ---

Kinda funny how many answers start with "It depends".

You've answered my question and thanks! I always thought it would keep running even at an idle but this isn't the first time I've been wrong.

Jack E/NJ · 02-22-2020, 05:34 PM

Are you gonna try it? Then tell us what happens? 8^) Jack E/NJ

rotorwrench · 02-22-2020, 07:13 PM

Alternators will do a better job of carrying the load when the battery is cut out but I wouldn't recommend anyone do it for more than a few seconds. As was mentioned, the old 3-brush generators depend on the battery to set voltage output. With no battery, the output will definitely go off scale high.

Ford updated stuff pretty regularly but the 2-brush didn't start to show up until the late 30s. We actually answer a lot of questions with that term at the beginning due to updates and variations in Fords production over the years. A specific year and model would lead to less use but not always. Ford changed things mid year in a lot of cases.

deuce_roadster · 02-23-2020, 10:54 AM

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The question that comes to me is WHY do you want to do that? I am trying hard to think of a reason to do this. I am very curious as to what this accomplishes. Like "if I drain the oil out of a running engine, will it keep running?"

jwaldrich · 02-23-2020, 11:52 AM

Quote:

Originally Posted by deuce_roadster

The question that comes to me is WHY do you want to do that? I am trying hard to think of a reason to do this. I am very curious as to what this accomplishes. Like "if I drain the oil out of a running engine, will it keep running?"

It was one of my methods of testing as to whether or not the generator was working. I have now installed a "used" generator with the same results when I disconnected the neg battery cable (positive ground).

The gauge on the dash indicates the installed generator is working but I was surprised to find that the car died when disconnecting the battery. I thought it would run.

Seems to me "somewhere" in my history I have done this before and the car continued to run but that must have been with an alternator.

JSeery · 02-23-2020, 12:03 PM

I have done this when having a boat battery problem. Back the boat into the water, take the battery out of the car but leave it running. Install the battery in the boat and offload it. Then go park the car and turn it off. This is with an alternator, not a generator.

flatheadmurre · 02-23-2020, 12:35 PM

Disconnecting the battery when running an alternator gives you voltage spikes up to 120v...for very short periods mS since the alternator stator is a big inductor(coil).
If you have any electronics in the car like fuel injection i wouldn´t try my luck.
Most cars with electronics has voltage clamps keeping it under 40v above that voltage regulators of ECU´s fry fast....but they take so much then you can toast them to.
Bulbs or a fan motors etc don´t care about it since it´s for a blink...but solidstate is fragile if unlucky.

JSeery · 02-23-2020, 12:43 PM

Well, I hate to be in this position! But here goes, I have disconnected batteries with the engine running may times and never seen an issue. Just lucky I guess. And I'm the one that doesn't like people saying "will I never had a problem", LOL. Next time I'm around that situation I'll have to throw a voltmeter on the system.

Here is an interesting video, but it's just something off the internet, so don't mean much. I'll have to do my own testing.

https://www.bing.com/videos/search?q...88E4&FORM=VIRE

flatheadmurre · 02-23-2020, 01:11 PM

Voltmeter is way to slow to show mS voltage spikes...you need an oscilloscope for it.
Worst is actually when you disconnect...you get what is called a load dump in geek language.
And Murres law says Murphy was a damn optimist...so anything will happen if i try it...lol

JSeery · 02-23-2020, 01:45 PM

Quote:

Originally Posted by flatheadmurre

Voltmeter is way to slow to show mS voltage spikes...you need an oscilloscope for it.
Worst is actually when you disconnect...you get what is called a load dump in geek language.
And Murres law says Murphy was a damn optimist...so anything will happen if i try it...lol

Interesting, thanks for the info.

rotorwrench · 02-23-2020, 07:08 PM

I had customers that would check their alternator output this way on the helicopters. The alternator is a 70-amp 24-volt unit with a 70-amp ampere meter. There is nothing in the aircraft that will pull near half of 70 amps so they couldn't tell if it was working by the amp meter unless the cut of the battery switch.

They finally started putting a low voltage warning light in the panel that fed off the alternator control unit. At least this way a person can tell if the system is working. A volt meter would have likely been a better choice than an amp meter for gauging alternator output.

34billct · 02-23-2020, 10:47 PM

If you have a FUN PROJECTS voltage regulator, disconnecting the battery will fry it.

fourfords · 02-23-2020, 10:54 PM

If you are trying to determine if your generator is working, disconnect the generator and hook it up directly to the 6 volt battery. If it turns, its working. Then determine the polarity, adjust the brushes, hook up the cutout.

jwaldrich · 02-24-2020, 11:53 AM

Quote:

Originally Posted by fourfords

If you are trying to determine if your generator is working, disconnect the generator and hook it up directly to the 6 volt battery. If it turns, its working. Then determine the polarity, adjust the brushes, hook up the cutout.

I'm "cheating" here. This issue is on my 1940 LaSalle but I figured the theory and tests would all work the same. There is no cutout on this generator.

I AM a fan of the Fun Projects cut outs and have them on all three of my T's. My Model A came with an alternator so I haven't screwed with that since it is working just fine.

So many cars and so little time...

02-22-2020, 12:08 PM	#1
jwaldrich Senior Member Join Date: Dec 2011 Location: Orting Wa Posts: 290	6 V Positive Ground On a 6 volt positive ground flat head V8, and if everything is working correctly, can I remove the negative cable from the battery while the car is running and expect the car to continue to run on the generator? __________________ John from Kapowsin T&A Guy

02-22-2020, 01:51 PM	#2
Kurt in NJ Senior Member Join Date: May 2010 Location: on the Littlefield Posts: 6,156	Re: 6 V Positive Ground it depends ----on a 3 brush with cutout at idle --no , ig engine running fast enough to charge and battery cable removed the voltage can go over 40 volts and if kept that way long enough smoke starts to come out of wires, points,coil can burn up, and any light bulbs that are on will burn out ----ending when the fried generator finishes itself off on a 2 brush with regulator that engine is running fast enough to be charging it will keep running, but it won't like it and the regulator has to work overtime to keep control ---

02-22-2020, 05:34 PM	#4
Jack E/NJ Senior Member Join Date: May 2010 Posts: 2,173	Re: 6 V Positive Ground Are you gonna try it? Then tell us what happens? 8^) Jack E/NJ

02-22-2020, 07:13 PM	#5
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,425	Re: 6 V Positive Ground Alternators will do a better job of carrying the load when the battery is cut out but I wouldn't recommend anyone do it for more than a few seconds. As was mentioned, the old 3-brush generators depend on the battery to set voltage output. With no battery, the output will definitely go off scale high. Ford updated stuff pretty regularly but the 2-brush didn't start to show up until the late 30s. We actually answer a lot of questions with that term at the beginning due to updates and variations in Fords production over the years. A specific year and model would lead to less use but not always. Ford changed things mid year in a lot of cases.

02-23-2020, 10:54 AM	#6
deuce_roadster Senior Member Join Date: Oct 2011 Location: Shelton, WA Posts: 3,799	Re: 6 V Positive Ground Sponsored Links (Register now to hide all advertisements) The question that comes to me is WHY do you want to do that? I am trying hard to think of a reason to do this. I am very curious as to what this accomplishes. Like "if I drain the oil out of a running engine, will it keep running?"

02-23-2020, 12:03 PM	#8
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: 6 V Positive Ground I have done this when having a boat battery problem. Back the boat into the water, take the battery out of the car but leave it running. Install the battery in the boat and offload it. Then go park the car and turn it off. This is with an alternator, not a generator.

02-23-2020, 12:35 PM	#9
flatheadmurre Senior Member Join Date: Apr 2015 Location: Sweden Posts: 3,045	Re: 6 V Positive Ground Disconnecting the battery when running an alternator gives you voltage spikes up to 120v...for very short periods mS since the alternator stator is a big inductor(coil). If you have any electronics in the car like fuel injection i wouldn´t try my luck. Most cars with electronics has voltage clamps keeping it under 40v above that voltage regulators of ECU´s fry fast....but they take so much then you can toast them to. Bulbs or a fan motors etc don´t care about it since it´s for a blink...but solidstate is fragile if unlucky.

02-23-2020, 12:43 PM	#10
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: 6 V Positive Ground Well, I hate to be in this position! But here goes, I have disconnected batteries with the engine running may times and never seen an issue. Just lucky I guess. And I'm the one that doesn't like people saying "will I never had a problem", LOL. Next time I'm around that situation I'll have to throw a voltmeter on the system. Here is an interesting video, but it's just something off the internet, so don't mean much. I'll have to do my own testing. https://www.bing.com/videos/search?q...88E4&FORM=VIRE Last edited by JSeery; 02-23-2020 at 12:58 PM.

02-23-2020, 01:11 PM	#11
flatheadmurre Senior Member Join Date: Apr 2015 Location: Sweden Posts: 3,045	Re: 6 V Positive Ground Voltmeter is way to slow to show mS voltage spikes...you need an oscilloscope for it. Worst is actually when you disconnect...you get what is called a load dump in geek language. And Murres law says Murphy was a damn optimist...so anything will happen if i try it...lol

02-23-2020, 07:08 PM	#13
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,425	Re: 6 V Positive Ground I had customers that would check their alternator output this way on the helicopters. The alternator is a 70-amp 24-volt unit with a 70-amp ampere meter. There is nothing in the aircraft that will pull near half of 70 amps so they couldn't tell if it was working by the amp meter unless the cut of the battery switch. They finally started putting a low voltage warning light in the panel that fed off the alternator control unit. At least this way a person can tell if the system is working. A volt meter would have likely been a better choice than an amp meter for gauging alternator output.

02-23-2020, 10:47 PM	#14
34billct Senior Member Join Date: May 2010 Location: westport ct. Posts: 166	Re: 6 V Positive Ground If you have a FUN PROJECTS voltage regulator, disconnecting the battery will fry it.

02-23-2020, 10:54 PM	#15
fourfords Senior Member Join Date: May 2010 Location: Lake Elsinore, CA. Posts: 413	Re: 6 V Positive Ground If you are trying to determine if your generator is working, disconnect the generator and hook it up directly to the 6 volt battery. If it turns, its working. Then determine the polarity, adjust the brushes, hook up the cutout.