HDX Voltage display

[Nev]

I've had two HDX's installed in my Bearhawk aircraft since new, with an ACM, Vertical Power PPS (front side of firewall), and an EarthX battery. Each display has a backup battery and these have been tested recently. The avionics etc was installed by an avionics company and have worked well. The aircraft has 240 hours on it.

There are two items that I'm unsure about.

1. Recently, the voltage display has been reading high. I did some troubleshooting and found two cables that needed tightening. That has solved the spurious issues. However, whereas the display voltage previously would typically read 14.2V, it now reads 14.7-14.9V when inflight (which triggered a high voltage alert). A multimeter on the battery shows 13.3V on the ground, with the EFIS reading 13.7V. The D37 pin 1 appears not to be connected, so the voltage seems to be displaying ACM voltage, and over reading by 0.4V. The aircraft has been starting well, even when below 0°c.

Is this anything to be concerned about or is it simply an indication error ? Can it be corrected ?

2. Because I've been paying more attention to the ACM display as a result of the above issue, I've noticed that the battery shows a discharge on the EFIS screen after initially fully charging. However it shows a discharge while still showing 14.7-14.9V. I'm scratching my head on this one, because to show a voltage that high I figure it must be receiving input from the alternator. I'm wondering if it is to do with the EFIS menu configuring where the shunt is installed in the system (position A,B or C,). My understanding is that the shunt is part of the PPS.

Any help appreciated.

 

[rjones560]

With the engine running and the alternator operational 14.5 volts would be normal. 14.8 is barely a little high. The high voltage alert can be changed in the software. I am curious what engine/alternator you have and what battery you are running. A lot of the external voltage regulators can be adjusted with a small screw. Without knowing specifics it is hard to help.

 

[Nev]

Here are the specs:

Engine - Lycoming IO540
Alternator - Planepower 99-1012
Battery - EarthX 900

Thanks.

 

[maartenversteeg]

Note that EarthX batteries have higher voltages then the regular lead based batteries

 

[Rhino]

They maintain amperage longer after startup too.

Shunt breakage

Those are too expensive. I thought you meant not flying 'at that time'. In any case, I was just more curious about the allowable methods rather than trying to directly critique what you had. Wasn't sure if that policy carried over from my military days into civilian aviation.

forum.flydynon.com

 

[rjones560]

Here are the specs:

Engine - Lycoming IO540
Alternator - Planepower 99-1012
Battery - EarthX 900

Thanks.

Here are the specs:

Engine - Lycoming IO540
Alternator - Planepower 99-1012
Battery - EarthX 900

Thanks.

The Planepower alternators have a pretty poor reputation in the homebuilt world. A quick look around Vans Airforce will show you lots of failures at 100-200 hours. The B&C starters and alternators will generally run to engine overhaul (2,000-2,500 hours) without any problems. They cost more and have an external voltage regulator that should be mounted behind the firewall, but they run just fine practically forever. I have 4 B&C products on my engine so I will tell you that I really believe in their products. They were also very helpful in re-assembling my front alternator in a different configuration to help me solve a clearance problem I had due to using a non standard engine, cowl and induction system. The took care of the issue for free and paid for the shipping themselves. I could not possibly say enough nice things about B&C. When the Planepower alternator fail, get a B&C.

I have the same EarthX battery in my RV10 with a Barrett Precision 540-X engine rated at 290hp. The EarthX battery whips my engine over quite quickly with my B&C starter.

The 14.8 voltage you are seeing is quite acceptable for the EarthX batteries as standing voltage is usually about 13.8 volts for the EarthX batteries.
The Planepower 99-1012 has an internal regulator so I don’t think you can adjust it the way you can with an external regulator. It is normal to see the alternator hike up to 60 amps right after an engine start, but it goes back down quickly as the battery charges. After that I see the battery alternately taking a charge and giving it back a little as the battery management system on the EarthX does its magic.

 

[Nev]

The Planepower alternators have a pretty poor reputation in the homebuilt world. A quick look around Vans Airforce will show you lots of failures at 100-200 hours. The B&C starters and alternators will generally run to engine overhaul (2,000-2,500 hours) without any problems. They cost more and have an external voltage regulator that should be mounted behind the firewall, but they run just fine practically forever. I have 4 B&C products on my engine so I will tell you that I really believe in their products. They were also very helpful in re-assembling my front alternator in a different configuration to help me solve a clearance problem I had due to using a non standard engine, cowl and induction system. The took care of the issue for free and paid for the shipping themselves. I could not possibly say enough nice things about B&C. When the Planepower alternator fail, get a B&C.

I have the same EarthX battery in my RV10 with a Barrett Precision 540-X engine rated at 290hp. The EarthX battery whips my engine over quite quickly with my B&C starter.

The 14.8 voltage you are seeing is quite acceptable for the EarthX batteries as standing voltage is usually about 13.8 volts for the EarthX batteries.
The Planepower 99-1012 has an internal regulator so I don’t think you can adjust it the way you can with an external regulator. It is normal to see the alternator hike up to 60 amps right after an engine start, but it goes back down quickly as the battery charges. After that I see the battery alternately taking a charge and giving it back a little as the battery management system on the EarthX does its magic.

Thanks very much for the detailed explanation, appreciated.