Parasitic Electrical Leakage

[Geico266]

I may be chasing a problem of parasitic electrical leakage and I need advice on how to test for it. I have a multimeter, but how do you (the correct way) use it to see if there is a current draw after shutting down the main & alt switches?

I have noticed my Odyessy battery looses a little power after sitting. Last time I checked it was 12.3v. I put a Battery Minder charger (for AGM batteries) on it and it was up to 13.2 after sitting for a day with the ground cable removed. My conclusion is I have a parasitic draw somewhere.

How can I test with a mutimeter to find which circuit it the leaker? The plane is an RV-9A.

As always I appreciate any advice in advance.

[Legal Eagle]

I'm sure others will send more eloquent solutions but here's an idea. If you attach a small 12 volt bulb to the negative post on the battery and the other bulb lead to frame ground and the bulb lights, some device is drawing current.

One by one, segregate the devices. Start at the breakers.

Of course, you can also use the amp portion of your vom.

[Geico266]

Originally Posted by Legal Eagle

Of course, you can also use the amp portion of your vom.

I burned up the fuse in that baby years ago but not knowing what I'm doing. lol

I'll try the light bulb trick!

[DanH]

No reason to believe you have a parasite draw problem. A battery voltage of 12.3 after sitting a while isn't unusual. That's about 60% of capacity for an Odyssey, assuming you have an accurate voltmeter. How long was it sitting?

The 13+ volts after charging tells you nothing. According to the Odyssey manual you must wait at least six hours after charging before doing a simple voltmeter check.

If you want to check for draw anyway, connect your multimeter in series between the + batt terminal and the + battery cable, with the meter set for amps or milliamps. Do not turn on the aircraft master switch or you'll need another fuse for your meter.

[mgomez]

Put the multimeter between either battery terminal (doesn't matter which one) and its cable. Open any fuses or breakers that are on the "hot battery bus," or whatever you call the loads that are always on.

Make sure the battery contactor is off. If the current isn't zero, then your leakage is through the battery contactor or its kickback diode.

If you need more help, please email or post your schematic.

[cytoxin]

disconnect negative cable and install a m/amp meter in line. a small current draw wont always light the light enough to determine a draw. anything over a few milli amps (25ma for cars ....driven daily) is too much. ive seen many customers leave cell phones plugged in all the time and they eventually take their toll on the battery. usually a couple of months. the light is a good quick test but can also be tricky due to charging capacitors and such that the light will glow for a while because of its resistance value and lead you to think you have a draw when actually you dont. its just taking a while to charge the components that will sleep. also a battery can surface discharge if between the posts are dirty and a little bit conductive. ex. lots of dust, some electrolyte or other moisture.a clean battery is a happy battery

[Geico266]

Originally Posted by DanH

No reason to believe you have a parasite draw problem. A battery voltage of 12.3 after sitting a while isn't unusual. That's about 60% of capacity for an Odyssey, assuming you have an accurate voltmeter. How long was it sitting?

It was sitting for a couple of weeks.

Originally Posted by DanH

The 13+ volts after charging tells you nothing. According to the Odyssey manual you must wait at least six hours after charging before doing a simple voltmeter check.

I did let it "rest" for 24 hours. 13.14 volts.

Originally Posted by DanH

If you want to check for draw anyway, connect your multimeter in series between the + batt terminal and the + battery cable, with the meter set for amps or milliamps. Do not turn on the aircraft master switch or you'll need another fuse for your meter.

I'll give it a try. You are probably right, I'm more than likey worrying about nothing, not the 1st time.

Thanks!

[David-aviator]

Originally Posted by Geico266

I'll give it a try. You are probably right, I'm more than likey worrying about nothing, not the 1st time.
Thanks!

I have 2 Odyssey batteries in my airplane and have been using them for some time. If you do not have a keep alive circuit hot wired off your battery, you have a problem.

To illustrate, I checked battery voltages this morning. The primary battery showed 12.2 volts, no surprise, it has several keep alive circuits connected to it. The back up battery showed 12.97 volts. It has no keep alive circuits. The airplane was last flown 5 days ago.

The Odyssey will hold a full charge for quite some time, like several weeks for sure. I think you have a leak somewhere. I bought a small digital volt/ohm meter at Walmart for $15 and it appears to have a feature to measure a load up to 10 amps.

[Geico266]

Well, I checked the battery after letting is sit for a day and it was still 13.14v. I checked the amp draw and it was zero. So I guess I'll see what happens after the plane sits for a week ready to go.

Thanks again for your help & comments.