On my JD 5105 I can measure 2.4 milli amps. drain and if I unhook alt. It goes away. Do alt. Normally have a drain through them? I suspected the rectifier assy. but local repair shop hooked it to his tester and it was to be fine. Tested reg. and it failed so put new one in. This thing still drains. I am just not sure if some alt. designs do have some constant leakage thru them or if none are too.
- Thread starter Mike M
- Start date
MarkB_MI
Well-known Member
- Location
- Motown USA
If it's an internally-regulated alternator, a few milliamps is normal.
Allan in NE
Well-known Member
Yep, you're right
The rectifier should have zero drain.
Look at the positive diodes; they are usually the naughtly children. One of those jokers is "bleeding".
Allan
The rectifier should have zero drain.
Look at the positive diodes; they are usually the naughtly children. One of those jokers is "bleeding".
Allan
That is normal draw and means nothing. 2 milliamps is 2/1000ths of one amp. Many new cars draw 50 milliamps when parked - 24 hours a day.
2.3 milliamp draw on a typical tractor battery of 70 amp-hour would result in a time frame of somewhere around 580 days to kill the battery. That's less discharge than a lead-acid does on its own with typical "self discharge" of 5-10% per month.
2.3 milliamp draw on a typical tractor battery of 70 amp-hour would result in a time frame of somewhere around 580 days to kill the battery. That's less discharge than a lead-acid does on its own with typical "self discharge" of 5-10% per month.
Most modern cars with alternators experience a few milliamps of battery discharge even with all off n setting there. If you have unhooked then hook up the battery you may notice very small sparkies but the drain may be less then how even a prefectly good battery will inherently self discharge when setting from chemical action.
John T
John T
I have an old Mercury Cougar and it's only driven about once a month and never had a drained battery. I did on a 1980 Cadillac Seville and it was the internal regulator. I installed a master switch on it since it wasn't driven very much. Hal
PS: It was installed in the negative battery cable to isolate it from being grounded. The military used this on almost all of their vehicles we tested.
PS: It was installed in the negative battery cable to isolate it from being grounded. The military used this on almost all of their vehicles we tested.
Texasmark1
Well-known Member
The leakage is in the voltage divider that powers the regulator. It is a string of resistors between the output to the battery and ground. It is a direct connection from the big output terminal and is not affected by the ignition key. There is some reverse leakage in the rectifier diodes but that is in the microamperes.
Mark
Mark
That's kinda what I was told but find it hard to believe?
I checked the old 1981 F350 and it showed 0 drain and has never given problems dispite sitting alot. The Fords use an external regulator and I was wondering if this design had anything to do with it.
This is the only other thing I have to check that doesn't have computers on it running all the time.
I checked the old 1981 F350 and it showed 0 drain and has never given problems dispite sitting alot. The Fords use an external regulator and I was wondering if this design had anything to do with it.
This is the only other thing I have to check that doesn't have computers on it running all the time.
Walt Davies
Well-known Member
It would take 1000 mili amps to drain your battery 1 amp in 1hr. Devided by 2.4 it would take 416 hours to drain it by 1 amp. You have around 100 amp hours in your battery so figure out how long it would take to drain it.
I wouldn't get to worried about that.
Walt
I wouldn't get to worried about that.
Walt
It is the Mexican cartel needing power so they steal a few milliamp each day from your battery. LOL I just could not resist.
Your alternator has an internal regulator so it will have a few milliamp draw. Like some one else told you it would take almost a year to draw a good battery down.
Now whether your battery is good is the question. I sold a few of the 05 series tractors. On just about every one of them we had to replace the battery when cold weather hit. They came with a real cheap low CCA battery. We up graded them to the highest CCA and reserve that would fit in the battery box. Then we had little trouble with them.
Your alternator has an internal regulator so it will have a few milliamp draw. Like some one else told you it would take almost a year to draw a good battery down.
Now whether your battery is good is the question. I sold a few of the 05 series tractors. On just about every one of them we had to replace the battery when cold weather hit. They came with a real cheap low CCA battery. We up graded them to the highest CCA and reserve that would fit in the battery box. Then we had little trouble with them.
Sounds like rectifier leakage. Conductive brush dust bridging terminals in an otherwise good rectifier is often the problem. I have had leakers that after a good cleaning with high pressure air and solvent, no longer leak.
2.4 MA is still not much of a leak, but also check the radio noise capacitor in or on the alternator if it has one, they also can leak a bit when they get old.
2.4 MA is still not much of a leak, but also check the radio noise capacitor in or on the alternator if it has one, they also can leak a bit when they get old.
MarkB_MI
Well-known Member
- Location
- Motown USA
Coupe, I think he meant that open (when reverse-biased) is good.
Open diodes are actually quite common. All you have to do is exceed the diode's maximum forward current rating. It will initially short, then blow open.
Of course this whole discussion of open and shorted diodes is silly with respect to the original post. A shorted diode will draw a lot more than a few milliamps. And the reverse leakage current for a typical silicon diode is minuscule, in the microamp range.
Open diodes are actually quite common. All you have to do is exceed the diode's maximum forward current rating. It will initially short, then blow open.
Of course this whole discussion of open and shorted diodes is silly with respect to the original post. A shorted diode will draw a lot more than a few milliamps. And the reverse leakage current for a typical silicon diode is minuscule, in the microamp range.
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