Electrical question

V

vern hodgson

Well-known member
Car is standing at idle, running fine, if I disconnect the battery ground should the car continue running off the generator?
 
Doing this should kill the engine on a stock Model A.

At idle, you are pulling all power for the coil from the battery. Generators don't put out at idle RPM.

What are you trying to figure out by doing this?
 
Jim/TX/GA said:
Doing this should kill the engine on a stock Model A.

At idle, you are pulling all power for the coil from the battery. Generators don't put out at idle RPM.

What are you trying to figure out by doing this?
Click to expand...

Just wondering if generator was charging enough.
 
It is not recommended at all to disconnect the battery while the engine is running.

If you do this at a fast enough engine speed where the generator is charging and the cut out is closed, the generator voltage will increase above battery voltage and this may burn out light bulbs and burn points etc. Just watch the ammeter, it will tell you if the generator is charging.

My opinion,

Chris W.
 
If you're concerned about the charge rate, what does the ammeter show ? That should show you your charge rate. If the system is stock the charge rate can be changed by moving the movable brush. The system should/will not charge at idle.
 
CWPASADENA said:
It is not recommended at all to disconnect the battery while the engine is running.

If you do this at a fast enough engine speed where the generator is charging and the cut out is closed, the generator voltage will increase above battery voltage and this may burn out light bulbs and burn points etc. Just watch the ammeter, it will tell you if the generator is charging.

My opinion,

Chris W.
Click to expand...

I agree. In the Model A, the battery is the regulator. At idle, the generator is usually not in the circuit because the cut-out has it disconnected to prevent the generator from discharging the battery. Once the engine revs up enough for the generator to put out more than 6.3 volts, it puts the generator in the circuit. At that point, you could disconnect the battery and the car will run off the generator. However, the generator is capable of putting out one heck of a lot of volts under no load of the battery charging. Maybe 20 volts or so at higher revs. Hopefully the coil will take that kind of voltage, but if you happen to turn on any lights, they will probably go in a flash. Bottom line is don't try it. :D
 
With a stock cutout and normal idle speed it's too slow of a speed to have the cutout contacts closed, if you have a diode cutout I would expect continued running if the ignition is good enough to work on 4 volts
 
While we all are using either an original or repop amp meter the idea was generally a bad one and that is why you do not see them on cars or boats much anymore.

Reason? All the charging and discharging amperage goes through a very week link... the meter!

Volt meters replaced amp meters many years ago. They run only on voltage and do not require heavy ga. wire since the amp load is not passing through the meter.

I have seen some folks that tour by pass the Amp meter (keep it there for looks) and then add a volt meter under the dash. A quick glance and you can see what the voltage is. at 6 volt will be running approx. 6.8-7 volts when receiving charge. 12 volt will go as high as 14.2 volts with full output.

By bypassing the amp with heavy wire it greatly reduces the change of fire under the dash which is never a good thing.
 
Thanks for all the input, I was curious because my battery was not charging, but it has been started often, allowed to stand at idle, and no driving for quite some time, guess that sprains it.
 
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