Dual Battery setup (ETX-900s)

Hidden deep in the schematic is the heart of the system, two EarthX ETX900-VNT Lithium batteries. The VNT versions of the batteries have vent ports that allow one to externally route the off gas with the supplied tubing. I have installed these in a Z-14 like configuration with one Main Battery and one AUX Battery with a cross-feed contactor between them. I am using my AUX bus as the Aircraft Power 2 feeder in lieu of running something like an IBSS system. So the start-up procedure will be like this:

1. Move the AVIONICS toggle from Off to AUX in order to power the backup power to the essential components. (I will make another post with my AUX power configuration). This will give me a Radio, PFD, Navigator, and a couple of other essential items.
2. Move the MASTER toggle to the "Batt" position. This will enable the main 2GA wire going forward to the starter.
3. Start the Engine
4. Move the MASTER toggle to the "Alt" position. This will enable the alternator.
5. Move the AVIONICS toggle to the "ON" position. This will let the VPX-PRO power up the rest of the avionics.
6. Move the X-FEED contactor to "ON". This will connect the MAIN BUS to the AUX BUS and allow charging of the AUX system.

The first thing to do to enable this system was to build a new battery box to accept 2 batteries. I kept the original location, but by using Lithium batteries, I was able to put to batteries in the place of the 1 original. I welded some 1"x2" 6160 Aluminum Angle to form a box with some .063 2024 to form the bottom of the box that rested on the 1" leg of the sides.

I then welded two lengths of 1"x2" facing forward and aft in order to give the box a couple of mounting points to the original 4 AN3 nutplates. This was in perfect alignment of the original two tie down points as well so I could use the standard hold down bracket.

The new batteries are a little shorter and a little wider, but they are really stable. Shown here is the right side without the electronics tray. See the other post about the avionics tray that I tied into the battery box.