SonexBuilders.net

Here is a copy of my Xenos schematic. Your comments welcomed.

I removed diodes I originally had because I didn't want the voltage drop. The Lifepo batteries need at least 14.2v for charging.

Overvoltage protection is from Perihelion Designs and back up in case that failed is to pull the CB. Either drops out the contactor in the B+ lead of the alternator. The main & B lead contactors are Gigavac dual coil so they pull very low current after the initial closure.

The fatwire indicated is large but lightweight wire from Perihelion Design. It is about 7/16" dia. whereas #2 tefzel is about 3/8" dia. (inc. insulation). But the fatwire is really lightweight. I may use it instead of the #8 indicated from the main contactor to main fuse block.

Rick Caldwell
Xenos 0057

If your main and aux batteries were at different levels of charge, is it possible you might exceed the 15A limit between the two as one attempts to charge the other one?

Chris,

The 15A circuit protection is there.

The soaring battery is not going to be connected to the main bus unless the engine is running + alternator charging. So there will be >14V on the system. Both batteries will have less than that so both batteries will be charged.

Rick Caldwell
Xenos 0057

Hi Rick. What alt are you using? You don’t show a voltage regulator and i see s note about internal regulation.

Gordon

Hi Gordon,

I don't know what brand it is. It is a 40A automotive alternator with an internal regulator on my CAMit 3300. My engine is still crated in my den with a cat bed on it. It's going to stay in the plastic bag in the crate in the house until I can do no more work on the Xenos except hang engine.

Rick Caldwell
Xenos 0057

Rick,
Is this your final schematic with backup battery?

Looks like a good setup. Normally all on. Time to glide, avionics switch off, then shutdown and kill the master.

Time to motor. Master on, started up, then avionics switch back on. I think you are better to keep it manual control with switches than try to automate with diodes.

Sorry for the delay, Bill. I just now saw your question. The answer is yes. The smaller battery is not a back up for the main battery. The small battery is for soaring with engine off. The main battery will not be on if the engine is off. That way the main battery will always have juice for starting. I could run the small battery down if I soared long enough but then I have have to start the engine on the main battery and let the small battery recharge. BTW, I plan to use an Earthx 680 for the main and the K2 battery for the soaring battery. The K2 is marketed for sailplanes for that application.

I am getting close to start wiring. I am doing all the detail work on the fuselage that I can before I start wiring. I am just now starting the lower intersection fairings now that the wheelpants and main gear fairings are complete. I may even finish painting the fuselage before I start on the FWF.

Rick Caldwell
Xenos 0057

Rick

Which K2 will you be using?

Carlos

Carlos,

The one Wings & Wheels sells. They only carry that one model. I don't know the #. The specs are impressive when compared to Earthx, however, the K2 is not a starter battery like the Earthx.

Rick Caldwell
Xenos 0057