Single Ground Buss?? Question clarified I hope

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?

A couple of people I respect have said it would be ok, but I'm looking for any potential issues.

I will be using two separate switches for the new batteries that are pull to unlock SPST.

Thanks

Kevin
92

I see no problem with that. I don't think electrons have changed too
much over the past 45 years.

Dan, 5J, BSEE 1972.

On 2/4/2017 7:56 AM, wrote:
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?

A couple of people I respect have said it would be ok, but I'm looking for any potential issues.

I will be using two separate switches for the new batteries that are pull to unlock SPST.

Thanks

Kevin
92

--
Dan, 5J

DAN,

Thanks so much. It will really simplify the nest of spaghetti under the panel this way.

Kevin
92

Good luck with that. The hardest part about a DC power system in a
glider is making the wiring look neat and tidy.

In my previous glider (Experimental), I had three batteries, two battery
switches (SPDT) and a single ground bus. I also had mounted on the
panel a digital volt meter
http://www.jameco.com/z/EMV-1200-Lascar-Electronics-Single-Hole-Mounting-2-Wire-Meter_2095040.html?CID=GOOG&gclid=CjwKEAiAlNbEBRCv 9uy4j4SWrgwSJAB5MqJFYTX5f69VJquiMDtHc57n7VTphhyuae RSWSVRN3cJPhoCecLw_wcB.
When voltage dropped to a particular level, I would turn on the second
switch and immediately flip the first switch down to the second
position, then turn the second switch off. I never had a problem with
that. After switching to LiFePO4 batteries, I never had to switch again.

On 2/4/2017 8:27 AM, wrote:
DAN,

Thanks so much. It will really simplify the nest of spaghetti under the panel this way.

Kevin
92

--
Dan, 5J

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

Yes, It is very busy, a numbered diagram and number wires, with Many bundles in wrap. The wiring diagram from the factory has over 50 wires going from place to place. Made some progress yesterday figuring out how to get everything mover over a little bit to get new instruments in and the new wiring set up.

Thanks again

Kevin
92

There is a plate with 3 post that everything is grounded to. That is what I am calling a negative buss.

Thanks,

Kevin
92

wrote on 2/5/2017 5:16 AM:
There is a plate with 3 post that everything is grounded to. That is what I am calling a negative buss.

Sounds like you have a proper single point ground.

--
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

Kevin, I have a DG-400, too, and contemplate adding separate battery(s) for intstruments, as you are doing. Where are you locating the new batteries, in the baggage area in front of the spar? Good luck with the project.

On Sunday, February 5, 2017 at 8:00:40 PM UTC-5, Paul Villinski wrote:
Kevin, I have a DG-400, too, and contemplate adding separate battery(s) for intstruments, as you are doing. Where are you locating the new batteries, in the baggage area in front of the spar? Good luck with the project.

Yes, made a tray from 2 inch angle and placed it just against the wall just behind your head. Tray is long enough that the two screws on each side that hold the trays in place in the spar box. This also makes it long enough that it cannot move forward as well as having it anchored with the two screws.

Make sure you use the wiring diagram. I will email it to you privately. It is a fairly complex system. The only small wires I left on the main switch, (which serves as a positive buss is 51, and one other. 51 supplies all the motor related electronics.

Lots of time and tylenol.

Send my your email and I email you the wiring diagram tonight.

Kevin soar AT gmail dot com

Kevin
92