Parasitic Drain?

A 6-volt lead/acid battery will have a higher voltage reading right after a full charge but will lose a tenth of a volt after it sets a while. This is normal from my experience.

The newer the battery, the less it will drop off. As long as it's above 6-volts, it should start the car but condition largely depend on how long it has been in service and how often it is used.
 
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Youngblood said:
Thanks Brent. Yes, I have an alternator and I checked it. It shows a draw of .9 amps so I believe that would be the reason the battery draws down if I leave power to the system. I will just need to make sure I cut the power to the car when I shut it off for a period of time.

Thanks,
Mike
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.9 amps is rather a lot. Most likely a rectifier diode has failed (there are three of them, pressed into the finned assembly). Rectifiers are available for not a lot of money, just be sure you get the right polarity.

https://www.ebay.com/itm/10SI-Delco...ectifier-6-12-or-24-Volt-/192813587816?_ul=IL
 
bbrocksr said:
I have to disagree with " a well functioning unit will have no draw at all."
A brand new alternator will have a minimal draw.

Diodes do not resist backflow 100% nor do they conduct current 100%.
Bill

P S I hate to agree with Brent but he's right.
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Yep, he is.
 
Hi; I called Nu-Rex and asked them about the draw. There is a draw on the alternators. There is always a small draw when the Battery is connected. 1 - 2 amps is not uncommon but they said it should not cause a significant voltage loss at the battery over time.

Mike
 
Master switch are nice to have, extra protection from theft and electrical draw, have one in every collector type car I own.
 
Youngblood said:
Hi; I called Nu-Rex and asked them about the draw. There is a draw on the alternators. There is always a small draw when the Battery is connected. 1 - 2 amps is not uncommon but they said it should not cause a significant voltage loss at the battery over time.

Mike
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Well, Nu-Rex is right. But I think that amount is a bit high, but, regardless they draw.

As mentioned, a good shut-off in a convenient location is a good thing.
 
On most alternators 50 miliamps is considered normal leakage. Anything above 80 miliamps in too much.

I quit using the 6-volt conversion alternators due to the high charging level of the voltage regulator. They just don't work like a normal alternator when they start messing with the original design.
 
I have a Nu-Rex which is essentially a 10si and I can park it for weeks with no significant drain. I do get a very slight reading on the electronic DVM, but still not enough to drain it, but I usually drive it several times a week. I do use the shut off switch when I park when I go out of town or on vacation.
 
At what point does it become non-parasitic. My 1930 Special Delivery has gremlins under the hood. If I leave my Nu-Rex 12V alternator connected I drain multiple volts from the battery in a matter of hours. Bad diode(s)? Bad regulator? Any suggestions from the sages in here?
 
Special Delivery said:
At what point does it become non-parasitic. My 1930 Special Delivery has gremlins under the hood. If I leave my Nu-Rex 12V alternator connected I drain multiple volts from the battery in a matter of hours. Bad diode(s)? Bad regulator? Any suggestions from the sages in here?
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If everything is stock and no additional add-ons, I would definitely suspect the alternator and have it checked out for either diodes or its internal regulator.


If you have a lot of add-on stuff, I would probably start there. Disconnect each one at a time and use an the ammeter of a VOM in series with each to see what kind of current each item draws when the car is off. You would hope zero, but ya never know.....


For that matter, you can also use the same ammeter connected in series with the alternator output pole to check for draw. It could be milliAmps which is too small to show up on the dash ammeter.
 
Another common problem is the brake light switch. Some of the reproductions don't work well and can just have enough contact to allow juice to flow to the brake light. I've seen more than one with a dim glow at night with the car setting at rest. Another problem can be with a pop out or ignition switch that doesn't completely break the circuit when shut off. If the points are closed, it can drain through the ignition coil.

I have a fuse puller and just pull the fuse out when the car is going to set for a while. This requires a fuse kit to be installed at the battery.
 
If’ing my A is not going to be started for awhile, I flip up the mat, pop the metal cover, wiggle the positive ground battery terminal off of the battery. I’ve done this for over 50’years! It works in an emergency like when at a car wash clean up the engine bay ( over 50 years ago) or when a starter switch sticks on ! Tom Wesenberg did this also RIP
 
The way I solved the problem was to put a cut out switch on the positive battery cable. Every time I park my roadster I snap the switch off. It eliminates ANY draw! Battery is always up when I go to start the car.
 
You will notice that the "good old boys" will always park their trucks on hills, especially if they will be parked for any length of time.
 
I measured voltage across the diodes and get roughly 0.5 volts BOTH ways. That sure seems like bad diodes and the likely gremlin under my hood. Kinda sad because it’s a 4 year old Nu-Rex 12V. Would’ve expected better quality from them.
 
I guess I must just be lucky then, I have an alternator on a 6 volt system, and the car sits for 6-8 months, and it starts right up every time. In my case, the alternator obviously does not drain the battery.
 
I don't have any parasitic draw with my generator, should I be worried?? Sorry, couldn't help myself. :)
 
I think some folks forget how well the original electrical system can work when it is properly maintained ��
 
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