Parasitic electrical drain

Hello. I am a new owner of an RV-6A (IO 360, CS Prop). I've flown 15 hours in the last twelve days of ownership and I'm loving it.

It does have a couple of snags that I'm working on rectifying. The previous owner mentioned the battery dying if he didn't fly the airplane regularly. Indeed I replaced the Odyssey 680 battery last week due to it's low capacity.

I am showing a continuous current drain of 3.9 to 4.6 mAmps. I know it is not much, but I would like to see if I can eliminate it. I work out of town and may be away for weeks at a time. It would be easier to solve the problem than remembering to disconnect the battery each time.

Here is a video: https://www.youtube.com/watch?v=UvmR1pibU7U of what is happening with the battery master off, and the multimeter hooked up in series between the battery NEG post and the battery ground.

The regular nature of the current switching leads me to suspect something digitally or computer controlled. Any suggestions on where to look?

The following is what I have for electrical equipment:

60 Amp ND alternator
Dynon D10 and D10A (with the various sensors)
Unison LASAR ignition
EXPBUS DC load center
Garmin 396 GPS
TruTrak DigiFlight II autopilot
Bendix King KY97A VHF COM
PS 3000 Intercom
XCOM 760 VHF COM
Remote Compass magnetometer in rear fuselage

That's the bulk of the equipment. Any help would be appreciated. Thank you.

John Swallow (the younger one)
Vernon, BC, Canada

What is connected between the master solenoid and the battery? I suspect the builder added an "always hot" lead to the battery.

Carl

Like Carl says it should be pretty easy to find. Look on the main contactor and battery for more than one wire other than the large one. Now finding where it goes to might be more of a challenge.

What a good opportunity to make a wiring diagram for your airplane!

Dave

I would look for a clock or something that has an always hot input to hold memory.

Thank you all for the quick replies. I just came back from a quick flight in the rain to wash off the detergent from washing the airplane in the rain.

I'm now on my way to pick up some PTFE paste for an oil pressure sensor replacement that I will do today and at that time will more closely investigate and map out my electrical system. As it is a slider, I have to spend some more time on my back to do so. Because of the EXPBUS, it will take me a bit of time to isolate where the various cables, wires and leads go. There is a spot for a keep alive circuit on the bus so I will try to see if it is utilized.

Will report back later.

John

Making progress

So. There were four leads attached to the "keep alive" circuit on the EXPBUS. When I removed all four leads, the current drain dropped to a steady 3.33 mAmps. No fluctuation. By re-attaching leads one at a time I determined the following:

Two of the leads (one protected by an automotive style Buss fuse) had no affect on the current drain when detached. I re-attached both of them.

Of the remaining two leads:

i) One brought the current drain up to 3.77 mAmps (0.44 mAmp increase from base 3.33 mAmps)
ii) One brought the current drain up to a 3.51 amps fluctuating to 4.12 amps in the same periodic basis as originally observed.

I will leave the suspect two leads detached and get ready to go flying as soon as the clouds clear and see what capability I have lost.

I now have the steady 3.33 mAmp drain to isolate and will look at the way my ammeter shunt is installed to see if it is continuously "live" and therefore causing the drain. I have been looking to change it's position anyway as the gauge in the cockpit fluctuates between positive and negative amps in flight and I think I'd rather measure the alternator output or the electrical load, vice the battery charge/discharge that I believe I am currently seeing. Mostly so I don't see negatives.

Thank you all for some encouragement. Honestly, I was very reluctant to mess around with the EXPBUS leads, but realize now that I will have to become comfortable with the electrical side of this airplane if I'm going to maintain it myself.

John

Is the battery contactor solid state? They can leak a small amount. Regardless, the battery contactor must be allowing a few milliamps to flow if it is the only thing connected to the battery positive terminal. Replace the contactor.
If you want to make sure the contactor is leaking current when off, disconnect the big fat battery cable from it. Then repeat the milliammeter test of the negative battery cable.

Check pin 2 on the Dynon D10A. It is a clock keep-alive circuit.
Dynon recommends that it not be connected if a GPS is connected as the GPS will set the clock at start-up.

A USB charger for a cell/iPad coming straight off the battery will pull it down. Even if nothing is plugged into it. I was leaving one plugged into the power adapter. Took a while to figure it out.