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1941 Cadillac 6 volt Battery charging level with engine running

Started by J. Russo, August 15, 2021, 03:27:22 PM

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J. Russo

I have a question about the 6 volt battery charging level while the car is running. I just want to make sure there aren't any adjustments needed to my voltage regulator.

I purchased a new 6 volt voltage regulator from NAPA.

I ran my engine for about 30 minutes.

With the engine idling in Neutral using a multimeter, my battery voltage is 6.4 volts.

When I accelerated to approximately 2000 RPM, the voltage reads 6.7 volts or a little more if I push it further. I didn't push it too much. I only ran at 2000 RPMs for about 20 seconds.

I turned the engine off and the battery voltage is 6.4 volts.

Is 6.7 volts an acceptable charging level at 2000 RPMs.

Thanks!
Thanks,
John Russo
CLC Member #32828

Glen

On a 6 volt system I usually set the voltage regulator to 7.1 volts.  But you have to be sure the battery is fully charged. 
Glen Houlton CLC #727 
CLCMRC benefactor #104

bcroe

Quote from: GlenOn a 6 volt system I usually set the voltage regulator
to 7.1 volts.  But you have to be sure the battery is fully charged.

Agreed.  That while being charged, V will drop off some after shutdown. 
Bruce Roe

las39

1939 LaSalle 5027
1941 Chrysler Royal Coupe
1934 Oldsmobile F34
1976 Moto Guzzi Convert

fishnjim

There's 2.1+ volts per Pb/H2SO4 cell so a six volt has three cells and will yield 6.3-.4 V when fully charged.   In order to reverse the current producing reaction you have to apply an overvoltage.   So around 7 V is average for charging(2X=14 if 12V), but you don't want to go too high either, you'll just convert the excess voltage to hydrogen/oxygen gases and dry out the battery and cause sulfation.   This should be in the procedure that came with the VR or in shop manual.
This overvoltage would be supplied by a generator for 1941s.   Generator has a fixed magnetic field, so output is somewhat linear, so they don't make much voltage at idle speed and these cars tend to idle slower (400 and up) than newer ones(6-700).   The battery is serving as the reservoir for having power at idle/not running, so to speak.   So when your moving, the battery will be "topped up"/replenished at the higher rpm provided it's run long enough.
You have to do a power draw test to test the battery/charging system.  Most of the big box parts stores offer this service free, they have the analyzer machine and just make sure they set it to 6 V.   
I keep a voltage meter installed in my generator cars to monitor charging/battery condition, those silly charge/discharge things are worthless.