G3X Shunt Signal Fuse - Page 2

MCA · #11 09-28-2019, 10:05 AM

Another option to consider is just not installing a shunt, to keep things simple. You can use voltage to determine if the alternator is working. The bus voltage is at about 12v when the alternator is off, and 14v when the alternator is on and engine running. If you turn on the alternator and don't see a rise to 14v then something is wrong.

Additionally, if you plan your electrical loads ahead of time you have a good idea that the alternator can power all the devices on the aircraft. Then during flight test you can turn everything on and validate that the system can maintain 14v over time.

Another option to think about...

Carl Froehlich · #12 09-28-2019, 02:31 PM

Quote:

Originally Posted by MCA

Another option to consider is just not installing a shunt, to keep things simple. You can use voltage to determine if the alternator is working. The bus voltage is at about 12v when the alternator is off, and 14v when the alternator is on and engine running. If you turn on the alternator and don't see a rise to 14v then something is wrong. SNIP

+1. Three RVs and none have a shunt.

So why install an ampmeter? If you are old enough you may recall that all cars had an ampmeter but none had a voltmeter. The reason is ampmeters at the time where easy and cheap to make. Voltmeters were expensive. Now you never find a car with an ampmeter. A voltmeter tells me everything I must know - even if running a standby alternator.

Some thoughts:
- If I ever really wanted to install and ampmeter I would use a hall effect sensor, not a clunky shunt.
- Anyone that really wants to use a shunt should never us "fusible links". Use a fuse. Why would you want to design in a wire melting your protection?
- If you want to take data, run the plane on your regulated power supply (never a battery charger) and see what the current draw is during various load conditions. One time test.

Carl

rocketman1988 · #13 09-28-2019, 04:45 PM

"...Anyone that really wants to use a shunt should never us "fusible links". Use a fuse. Why would you want to design in a wire melting your protection?..."

That is EXACTLY what a fuse is; a wire that melts to break the circuit.

I know what you mean though, at least the fuse is contained and replaceable.

I am still curious as to WHY a previous poster had his wires burn up; there should be very little current in the wires going from the shunt to the GEA24...

DRMA · #14 09-28-2019, 07:40 PM

Quote:

Originally Posted by rocketman1988

"...I am still curious as to WHY a previous poster had his wires burn up; there should be very little current in the wires going from the shunt to the GEA24...

While there is very little current going to the GEA 24, if one of those wires were to come into contact with ground (e.g. insulation were rubbed off with vibration, cut, etc.) you would then have a direct short from the alternator or battery to ground! The current flow in that case could be a couple hundred amps.

rocketman1988 · #15 09-28-2019, 07:46 PM

Hence the melted wire (fuse). So it was likely mechanical damage to the wire that caused the problem...

AlexPeterson · #16 09-28-2019, 08:17 PM

Here's a picture of the simple blade fuse/faston in-line fuse that I described in an earlier post:

Behind the silicone tape are two blade fuses and four fast-on connectors. Can't get any simpler than this. Here you can see the fuses peeking out:

Carl Froehlich · #17 09-29-2019, 08:10 AM

Alex,

You may want to consider covering those exposed terminals.

Carl

sibriggs · #18 11-16-2019, 03:56 PM

Hi, I need help, My electrical data is not being displayed correctly.

Shunt is inline between the main battery contractor and the VPX. All has been working fine for 2 1/2 years. Now I'm seeing reading of 0 or 1 amp on the G3X screen, instead of the normal 8 to 10 amps draw I'm used to seeing.

When I look at the engine data for the flight, I see many minutes of 0 amps then a 13 amp spike then 1 amp for a number of minutes then back to 0 amps then another spike of 15 to 10 amp a few minutes later, then back to 1 amp then 0 amps again.

Batteries are charging at 13.8 to 14.1 all the time, VPX amp readings for various components are showing normal amp draw per circuit.

So I thought wire frayed or chaffing, tested continuity from the GEA24 plug J243 to the shunt... no shorts, no issues obvious. The wire is a shielded twisted pair as specified in the G3X install manual. Wired to pins 36 and 37 in J243 plug.

Don't really know how a shunt does it works, but it doesn't seem to have any visible issues. No loose connectors or screws. The shunt looks just like it did when I installed it.

No other issues showing up in the G3X coming from data supplied by the GEA24.

Any thoughts would be most appreciated. Would like to figure it out short of swapping out the GEA24 and or the Shunt.

Shunt was purchased and is the one listed in the Stein catalog for the G3X installation.

Brantel · #19 11-16-2019, 04:03 PM

I used a fusible link a-la Bob Knuckles way back when I built the RV7. Still going strong with no issues.

tgmillso · #20 11-17-2019, 05:05 AM

Hi Steve,
I?m not sure if this will solve your issue, but today I finally test flew my aircraft with new fuses, and my current fluctuation issues went away. Even though the glass fuses looked fine, they had a fracture at one end internally that would cause trouble only when affected by a certain frequency vibration. Replaced with new fuses the problem has gone. I will soon be changing out the glass fuse holders to waterproof inline blade fuse holders which look to be more robust.
Tom.