Ammeter Shunt - Help me connect the dots!

[alpinelakespilot2000]

I'm using the Dynon ammeter shunt and would like to place it in position A so that it measures current flow in and out of the battery. However, I'm having trouble figuring out what that means in terms of what needs to be connected to what. See Dynon manual picture:



I've labeled my system with letters at each possible junction. If I want to measure current flow in and out of the battery, by using Dynon placement "A", between what two letters should I place the shunt (labled as H and G in my picture)?



Thanks for any help you can give.

[AltonD]

with your drawing, the shunt would need to be between C and D and your loads going to the aircraft would have to come off at D. This will show current into and out of the battery. Normal in flight amps should be low once the battery has charged up.

Orange/green wire to D and orange/purple to C. If the meter doesn't move in the direction yo want, swap the leads.

[Davepar]

I agree with Alton.

Assuming:
-battery positive is wired to A in your picture
-main bus is wired to D

You would put the shunt between C and D to measure current in/out of the battery.

However, consider this. You can tell when your alternator has gone out to lunch when the voltage on the bus is less than 14v. In that case, it would be helpful to know the current draw of the aircraft loads (i.e. position C in Dynon's diagram) so you can intelligently manage the power remaining in the battery.

To do that just wire J to H, G to D and you're done.

Just another option for you to consider.

[gmcjetpilot]

Here is you pic with some notes: (click once or twice to enlarge)
(edit fixed boo boo)

First I would recommend a LOAD (amp) meter to determine how hard your alternator is working. The LOAD meter works during flight. It tells you how many amps your alternator is putting out. That is important. It does nothing with with the engine not running or alternator off line. (Load meter between alternator and first relay or in your case the Bussman fuse.)

The BATTERY (amp) meter (like a Cessna with center and +/- scale) only works on the ground when the engine is not running. It only tells you if the battery is being charged or is being drained. In flight after the battery charged and is just sitting there, so the LOAD meter just sits there doing nothing. Boring and no info that is useful on a daily basis. (Battery meter between battery and buss. If you have multi busses that feed in parallel or dual batteries you are not going to be able to monitor all that with one shunt.)

Some justify the battery meter because if the alternator goes they SAY they will know how much drain they have. Well hooey. A Battery (amp) meter will not tell you have long you have left. The volt meter is more critical at this point, post alternator failure. If your alternator goes off line, you shed nonessential load and land. You should know about what your drain was. It will be what your load (amp) meter said before you lost the alternator. However you should know when you get to essential items what your amps are and how long you can run on battery alone. More about that below.

A LOAD (AMP) METER IS EASIER TO INSTALL AND GIVES YOU MORE DAY IN AND OUT INFO THAN A BAT METER, IMHO.

WHAT IS MORE IMPORTANT is voltage with the alternator off line. The VOLT meter and voltage give a direct battery SOC, state of charge. For an Odyssey battery the SOC schedule is:

Approx SOC numbers (see Odyssey owner manual for chart)
12.8 volt 100%
12.6 volt 80%
12.2 volt 50%
12.0 volt 34%
11.8 volt 20%

You get down to 10 to 11 volts, things will get start to go dark. Some electronics will work well below 11 volts. Most Garmin will go down to 10 volts.

SOC is the capacity in precentage. There is no need to get into detail but in general if you keep the same CURRENT or AMPs the battery will discharge at a faster and faster rate.

If you are flying sans alternator you are not going to break out the calculator and do math to determine the time you have left. To be fair voltage is not really going to tell you much, but if its falling fast and getting into the mid low 11's you are going to run out of juice sooner than later. ALSO to be fair knowing your AMP drain with a BATTERY (AMP) METER (no alternator) IS NOT GOING TO TELL YOU HOW LONG YOU HAVE LEFT EITHER!

HOWEVER you should have a good idea of what you MIN essential current drain is. The Odyssey PC680 should last. Odyssey published drain time from fully charged 100% to 10.02 volts at 10 amps of a little over 1-hour. That voltage is real low so let's split the difference, say 11.5 volts, you should about 30 min to from 12.8 volt peak to 11.5 volts.

My MIN emergency drain, electronic ignition, electronic flt/eng instruments, mater relay, Com in receive totals 4.2 amps, practical 5.7 amp load with transponder. Any lights adds from at. All I know is I have about +30 min with 10 amps, assuming the battery is in good condition.

[alpinelakespilot2000]

George,
Does the more recent picture below depict a proper installation for what you describe as a "load" meter? (This is also, I believe, Dynon version B, shown above.) If so, for ease of wiring, it would work really well with what I've already mounted and wired. (I haven't mounted the shunt yet, it's just there with double stick tape, but the current limiter is.)



Given that I've already bolted my 60amp ANL limiter to the firewall, getting the shunt between that and the battery/starter relays to provide a "battery meter" (version B) would be pretty tough, unless I want to move the ANL somewhere else and leave extra holes in my firewall. Alternatively, the method Dave suggests above (version C) would work pretty easily but that would just tell me how much power I'm using. From the voluminous debate I've already read in the archives, it seems like most people choose either version A or version B (?).

Any other thoughts? My engine from Aeroport just shipped so I'm ready to put it on as soon as I get this figured out!

[gmcjetpilot]

Yea sure that is it. That is what I would do.

PS disregard the buss feed in my previous (fixed, ok now), your last version above is correct and awesome!

One comment, pic can't show this but that brass tie from the starter relay to the Bussman thing, looks close to the metal fire wall. I am just saying, may be put some fiberglass sleeve insulator or sump-tin? It may be a mile away I can't tell, but its a dead short of the battery to ground with NO fuse, OUCH! Of course as it welds its way though the firewall you will turn the master contactor off. (I am kidding but I just get nervous seeing exposed brass ties. I know its been down 1000's of times successfully but the way it bends on the firewall side might be a little close? May be you can flip it around and put some insulation on it. Even liquid insulation in a tube would be better than nothing.

Do this, seriously
Have some one go into the cockpit and push of the firewall in that critical location (like some one might do with their foot). Than grab the starter contactor and yank on it side to side (while your buddy pushes on the firewall in that critical location). There is this dude named Murphy and he's a jerk! Ha-ha nice work; have fun hanging the engine. Make sure the shunt is perfectly level with in 0.0001 degrees.......ha-ha kidding again.

[alpinelakespilot2000]

Originally Posted by gmcjetpilot

One comment, pic can't show this but that brass tie from the starter relay to the Bussman thing, looks close to the metal fire wall. I am just saying, may be put some fiberglass sleeve insulator or sump-tin? It may be a mile away I can't tell, but its a dead short of the battery to ground with NO fuse, OUCH! Of course as it welds its way though the firewall you will turn the master contactor off. (I am kidding but I just get nervous seeing exposed brass ties. I know its been down 1000's of times successfully but the way it bends on the firewall side might be a little close? May be you can flip it around and put some insulation on it. Even liquid insulation in a tube would be better than nothing.

Thanks George. Actually the copper strip between the starter relay and the ANL limiter is a full 1/2"+ from the firewall. It's just the angle of the pic that makes it look close. However, I will do the firewall push test you suggest just to make sure and/or twist the copper bar 180-degrees and/or add some type of insulation.

Having said all that, one thing that has been bothering me too for a while is all the exposed copper that is per Van's plans. Obviously it's all on the hot side of the battery. Van's is careful to suggest using boots over the 2AWG battery cable terminals, but says nothing about covering the copper bar. Anyone have any suggestions about whether there is something handy that would protect/insulate those bars? I've thought about just using a piece of heatshrink over them, but don't have any other ideas (and I'm not familiar with the liquid insulation George is describing).

Thanks again for the help. As always, if anyone sees anything that looks kinda funky, let me know please!

[Norman CYYJ]

Its a good idea to tin all the copper. It will stop any major corrosion. In the marine industry it is mandatory.

[Mike S]

Originally Posted by alpinelakespilot2000

Anyone have any suggestions about whether there is something handy that would protect/insulate those bars?

The same boots as you have used on the cable will work, as you mentioned heatshrink will work, you can use multiple layers of it.

You can get nylon tubing at the hardware store in various diameters, an inch or two costs next to nothing, pick a size that will slip over the buss bar when you flatten the tubing. You could also use the boots on this.

Good luck.

[gmcjetpilot]

Originally Posted by alpinelakespilot2000

Thanks George. Actually the copper strip between the starter relay and the ANL limiter is a full 1/2"+ from the firewall. It's just the angle of the pic that makes it look close. However, I will do the firewall push test you suggest just to make sure and/or twist the copper bar 180-degrees and/or add some type of insulation.

Having said all that, one thing that has been bothering me too for a while is all the exposed copper that is per Van's plans. Obviously it's all on the hot side of the battery. Van's is careful to suggest using boots over the 2AWG battery cable terminals, but says nothing about covering the copper bar. Anyone have any suggestions about whether there is something handy that would protect/insulate those bars? I've thought about just using a piece of heatshrink over them, but don't have any other ideas (and I'm not familiar with the liquid insulation George is describing).

Thanks again for the help. As always, if anyone sees anything that looks kinda funky, let me know please!

Half inch you are fine, don't worry about testing it.

Its called liquid tape
http://www.plastidip.com/industrial_...cal_Insulation
http://www.thetapeworks.com/liquid-tape.htm
http://cableorganizer.com/insultherm-spark/#prices

Actually now I think of it, from a recent discussion Permatex® Ultra Copper® Maximum Temperature RTV Silicone stuff is awesome. It's copper in name only. I called them, just curious and its a very good insulator. If you scuffed the copper buss strap and coat / encapsulate it, the dark red goop, it will look nice and not so unfinished. Permatex is avaiable at any car place, the liquid tape I don't know where they have it.

Dropping a wrench or screw driver on the buss feed bars it might cause 4th of July. Can you imagine if it jams between the firewall and strap! I could also put my wild scenario hat on; say in a crash metal crumples, subjecting the buss straps to grounding? Pretty far fetched.


Another idea is a sleeve made with fiberglass or other material. If you Google "wire braided sleeving" you will find all kinds of vendors from wrap for the brass straps. Many places sell by the foot.
http://www.techflex.com/prod_SPB.asp
http://cableorganizer.com/insultherm-spark/
http://cableorganizer.com/wire-management/
http://www.aircraftspruce.com/catalo...lesleeving.php


Yes, I always wondered about Van's set up. However open copper buss bars have been used for a century, in all manner of power distribution systems. As long as nothing grounds, you're cool. However I think covering those open buss bars might be a good idea and give it a finished look?


[COLOR="Blue"]Norman CYYJ - "Its a good idea to tin all the copper. It will stop any major corrosion. In the marine industry it is mandatory."[/color] This would be overkill but you can buy these fiberglass sleeves of all diameters, colors and weaves to protect electrical stuff or items from heat.
Good idea!