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TR2/3/3A TR3B alternator leak

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T

TFB

Jedi Knight
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My 1 yr old battery seemed to drain over the holidays the first time I left it connected.Only continuity to ground is from the alternator(40a kubota type) output terminal 27kohms,measured with a high quality digital mutimeter.
I have no control box.Alter. is connected direct to battery at soleniod.Battery is 700 ca,RC@25a 120 mins.I think the load would .0004a so am thinking the battery may be going.
Is this right and normal,and what is the time that this trickle will depleat battery.
Thanks
Tom
 
TFB said:
My 1 yr old battery seemed to drain over the holidays the first time I left it connected.Only continuity to ground is from the alternator(40a kubota type) output terminal 27kohms,measured with a high quality digital mutimeter.
Click to expand...
The problem with that approach is that your multimeter uses only a small voltage for measuring resistance, which may not be enough to turn on the diodes or transistors (in the internal voltage regulator). The leakage current may be substantially higher with 12v from the battery applied. I would suggest measuring current directly, with the battery connected.

25A for 120 minutes is 50 amp hours; so it should take roughly 50/.0004 hours for 0.4 ma to drain the battery. That comes out to something like 15 years, which is less than the self-discharge rate. ("Normal" self-discharge is given as about 4% per week) So unless the current goes up under some conditions (like 12v applied or when the dew settles), I don't think you can blame the alternator.

If disconnecting the battery stops it from discharging in a few weeks, though, that pretty well proves that it is something going on with the car. FWIW, I've had similar problems several times that were eventually traced to moisture condensing from the air (dew). On my 1970 Audi, the relay for the rear window heater would turn itself on, apparently due to contamination of the relay base combined with evening dew. On the motorhome, it was apparently just mud caked around a connection under the body. When it got damp, the mud would conduct enough to sap the starting battery over a matter of weeks.
 
The best check for the car drain is to disconnect one battery lead and reconnect it through an ammeter. You will see exactly what is being drawn. It should be near zero. If it is, the battery is going...or it is not getting charged. If it is about a quarter amp or more, there is something going on with the car itself.

John
 
Thanks Randall and John
With meter on 30ma scale I got .5Ma between battery pos terminal and pos. cable with alternator and neg cable connected,so will take a better look at battery.
Tom
 
Like Randall said, that would take years to drain the battery, so the car wiring sounds good. Now check that the generator is putting out around 14 volts. If it is, then the battery is the culprit!

If you aren't getting around 14, then time to look at the generator and regulator.

John
 
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