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Old 07-27-2021, 08:08 AM   #21
rotorwrench
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Default Re: 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.

Last edited by rotorwrench; 07-27-2021 at 08:49 AM.
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Old 07-27-2021, 12:26 PM   #22
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Default Re: Parasitic Drain?

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Originally Posted by Youngblood View Post
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
.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-...3587816?_ul=IL
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Old 07-27-2021, 12:36 PM   #23
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Default Re: Parasitic Drain?

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Originally Posted by bbrocksr View Post
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.
Yep, he is.
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Old 07-27-2021, 12:38 PM   #24
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Default Re: Parasitic Drain?

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Originally Posted by Badpuppy View Post
.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-...3587816?_ul=IL



Thats a draw that should be addressed. And, yep, its an easy fix and parts should be available.
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Old 07-28-2021, 12:40 PM   #25
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Default Re: Parasitic Drain?

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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Old 07-28-2021, 01:37 PM   #26
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Default Re: Parasitic Drain?

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Master switch are nice to have, extra protection from theft and electrical draw, have one in every collector type car I own.
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Old 07-28-2021, 05:18 PM   #27
Patrick L.
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Default Re: Parasitic Drain?

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Originally Posted by Youngblood View Post
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




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.
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Old 07-28-2021, 05:36 PM   #28
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Default Re: Parasitic Drain?

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.
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Old 07-28-2021, 10:47 PM   #29
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Default Re: Parasitic Drain?

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.
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Old 05-02-2023, 07:34 PM   #30
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Default Re: Parasitic Drain?

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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Old 05-02-2023, 10:26 PM   #31
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Default Re: Parasitic Drain?

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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?

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.
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Old 05-03-2023, 10:14 AM   #32
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Default Re: Parasitic Drain?

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I tend to get self-excited, happens all the time.
Ya but at your age what good does it do you!
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Old 05-03-2023, 10:32 AM   #33
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Default Re: Parasitic Drain?

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.
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Old 05-03-2023, 11:58 AM   #34
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Default Re: Parasitic Drain?

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
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Old 05-03-2023, 12:17 PM   #35
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Default Re: Parasitic Drain?

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.
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Old 05-03-2023, 08:27 PM   #36
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Default Re: Parasitic Drain?

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.
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Old 05-03-2023, 09:03 PM   #37
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Default Re: Parasitic Drain?

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.
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Old 05-04-2023, 07:25 AM   #38
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Default Re: Parasitic Drain?

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.
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Old 05-04-2023, 12:43 PM   #39
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Default Re: Parasitic Drain?

I don't have any parasitic draw with my generator, should I be worried?? Sorry, couldn't help myself.
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Old 05-04-2023, 04:15 PM   #40
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Default Re: Parasitic Drain?

I think some folks forget how well the original electrical system can work when it is properly maintained ��
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