||05-16-2019 09:05 AM
Parasitic battery drain
Here is an interesting question for the group. My wiring is now complete and have configured everything that I can until the aircraft is moved to the airport. While completing some other fiberglass parts, my electrical system sat for a couple of weeks. One day to break the monotony, I turned on the panel to bask in my work. Nothing happened. My main battery was dead.
Now I know that you do not know the specifics of my system, but basically I have a two buss system. A main and an essential. Each has an EarthX battery on it.
My first thought was a bad EarthX battery. It took a charge and I left it on the bench for two weeks recording the voltage each day. Over two weeks the voltage dropped from 13.8 to 13.3. Did not see any issue with that.
My next step was to swap batteries. My essential buss battery which was still at 13.3v was moved to the main buss. The old main buss battery was moved to the essential buss. Two weeks went by and the battery installed on the main buss was dead.
Ok, the problem was definitely with the main buss. After recharging the battery, I disconnected the main battery cable and installed my Fluke between the battery cable and the positive battery terminal of the EarthX to measure amperage. The Fluke was reading 27 mA. A discussion with the engineer at EarthX revealed that their battery would last about 14 days with this load. That matches what I am experiencing.
Next step was to disconnect each lead in my system until the culprit was found. One by one I disconnected the leads to the VPX, starter contactors, EFII Bus Manager, seat heater relay, etc with no change to the 27 mA current flow. When I disconnected the main B lead at the alternator, the current went to 0. Just for grins, I reconnected it, verified that the 27 mA current returned, and spun the alternator. Spinning the alternator had not effect but I had to rule it out. Disconnected the alternator and the current went to zero.
The alternator and external voltage regulator were sent to B&C for evaluation and so far they cannot find any fault with it. They have my wiring diagrams and are working with me to find a solution. I am reaching out to the group to help me look at this from a different perspective and other ideas.