wrote on 2/4/2017 6:56 AM:
Reworking my DG 400 electrical system. Adding 2 batteries for instruments only and keeping main batts for motor related electronics and starter.

I have removed all of the positive wires supplying the breakers that are not motor related. At present there is one main ground buss.

Some of the instruments already have breakers and positive wires (original and in bundles) from the breaker to the instrument and negative (also in bundles) to the ground buss. I have left these in place. I will run new positive wires from a new positive buss to supply the breakers, and also other instruments.

Would I create any problem using this common ground buss for the motor related electronics, AND for the instruments which will be supplied by the 2 new batteries which are a different chemistry?(LiFePo4) The ship's chemistry is lead acid.

So the main question is DOES USING THE SAME GROUND BUSS FOR BOTH SYSTEMS CAUSE ANY POTENTIAL PROBLEMS?

I'm not sure what you mean by "buss", but typically, the instruments use
a "single point ground". The instrument point can be separate from the
engine connection to ground (battery negative), but connected to it with
a (preferably) short, large wire (large enough to have less than, say,
0.1 volt drop).


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "A Guide to Self-Launching Sailplane Operation"

https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf