Battery voltage indication LX9050
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Ian Molesworth
May 14, 2025, 6:16:52 AMMay 14
to LXNav Soaring Glider Equipment User Discussion Group
Anyone else getting wierd indications from their LX9xxx in flight?
One or two of us are getting rapidly declining battery voltage indications, to the point of low voltage alerts but they seem to be erroneous.
I have 25Ah Life AND 12 Ah batteries. Start flying and voltage indication goes down in 30 minutes to alert level. Switch batteries and it stabilises at 13.x, switch back and it's fine for the rest of the flight!
Adam Sayer
May 14, 2025, 6:22:59 AMMay 14
to Ian Molesworth, LXNav Soaring Glider Equipment User Discussion Group
Ian, there's a similar discussion on GPN funnily enough.
Are your batteries all on the same chemistry? And if so, is the battery profile set correctly in (if I remember correctly) Hardware > Battery Types?
For LiFePO, I found the LX default profile would cause low battery alerts within a few minutes of powering the instruments. So I created a custom profile that better reflects the discharge curve of LiFePO4. That stopped the alerts.
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Ludovic Launer
May 14, 2025, 7:38:33 AMMay 14
to LXNav Soaring Glider Equipment User Discussion Group
What do you mean by "custom profile" ? you changed the offset and modified the low battery threshold value ?
Antoine Megens
May 14, 2025, 8:59:13 AMMay 14
to LXNav Soaring Glider Equipment User Discussion Group
Yes, same here. We have LX9050 Club edition with 2x 10Ah LiFePo4 in parallel with a schottky diode.
Last season no issues whatsoever. This season complaints about "Low Battery" in flight.
Op woensdag 14 mei 2025 om 12:16:52 UTC+2 schreef Ian Molesworth:
Ian Molesworth
May 14, 2025, 9:00:51 AMMay 14
to Antoine Megens, LXNav Soaring Glider Equipment User Discussion Group
Ah ha! Something smells a little funny!
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Adam Sayer
May 14, 2025, 9:04:06 AMMay 14
to Ludovic Launer, LXNav Soaring Glider Equipment User Discussion Group
That's right, but you can also change the Empty and Full threshold (as well as the Low and Offset) parameters.
You go to Hardware > Battery Types > Types and select Custom.
Ian, no idea on yours! Good luck and do update on how you get on.
To view this discussion visit https://groups.google.com/d/msgid/lxnav-user-group/50366e56-5749-4929-b65f-393f9937ac35n%40googlegroups.com.
Antoine Megens
May 14, 2025, 9:08:10 AMMay 14
to Adam Sayer, Ludovic Launer, LXNav Soaring Glider Equipment User Discussion Group
Hi Adam, "So I created a custom profile that better reflects the discharge curve of LiFePO4. That stopped the alerts."
Can you maybe share your custom profile settings?
Op wo 14 mei 2025 om 15:04 schreef Adam Sayer <ads...@gmail.com>:
Message has been deleted
Ian Molesworth
May 16, 2025, 11:40:15 PMMay 16
to K. R., LXNav Soaring Glider Equipment User Discussion Group
Just to confirm its not my batteries I ran my capacity test setup twice onķ each of my batteries. A 2.75 A load with a voltage logger. Both batteries are within 1 Ah of their expected capacities. Its not the batteries!
The set points are not the issue. The issue is the very rapid apparent drop off in indicated voltage over perhaps 30 mins which would imply that I am drawing perhaps 20 A from my battery. Clearly that's not happening.
To view this discussion visit https://groups.google.com/d/msgid/lxnav-user-group/4c1d215d-d3a8-4978-9a34-5f6266e889b9n%40googlegroups.com.
Three Uniform
May 17, 2025, 10:00:58 AMMay 17
to LXNav Soaring Glider Equipment User Discussion Group
I had the exact same problem description many years ago.
Good fully charged batteries but quick voltage drop.
Not LXNav related, but my old Dittel radio radio started blinking.
After many hours of evaluation, I found that SH on my V2C had installed a 25-wire printer cable as wiring harness under the seatpan to the panel. A printer cable has very thin wires.
They were wise enough to run 3 wires in parellel for the +12V, but they were running all the ground (power and signal) through a single strand of the very thin printer cable wires.
This created a significant voltage drop.
I ripped out the printer cable and installed a proper gauge Tefzel wiring harness (12awg for power)
That solved my problem.
My recommendation for your case: In case it turns out to be not a software problem on the LXNav, measure the voltage drop on both +12V and ground between the battery terminal and the LXNav connection under full system load (i.e. radio transmitting) to check if your cabling is ok.
Julian Rees
May 26, 2025, 8:00:32 AMMay 26
to LXNav Soaring Glider Equipment User Discussion Group
I've now had 3 people at our club reporting the same strange behaviour. The voltage measured on the LX8/9xxxx will drop quite rapidly over the first 30-60 mins of flight, but the (if you do not switch batteries) the reported voltage will then gradually rise & remain constant for the remainder of the flight. Seems to only happen with LifePo4
In my case voltage drops rapidly from 13.4 to 12.4V, then rises back to 12.8V and stays there for 3-4 hrs (LX8040). Unfortunately I dont have any alternative measure of voltage but I've measured voltage drops etc on the ground & there does'nt seem to be anything unusual. I have nothing that is drawing current such as recharging Oudie or phone that accounts for this......
My suspicions are either that it is a BMS issue in the Battery or something odd in the LX software. It does seem to have started doing this about 12 months ago so might be a software change....
Ian Molesworth
May 26, 2025, 8:20:03 AMMay 26
to Julian Rees, LXNav Soaring Glider Equipment User Discussion Group
I very much doubt it is a problem with the battery.
I have a battery load/capacity tester and I test my batteries at the annual. When I got this first I tested my batteries ( 1.7 A load ) and the voltage decays precisely as it should ..... steadily towards the waterfall point when it dies.
The capacities of my batteries have not changed more than about 100 mAh over the 5 years they have been in use. ( negligable )
Ian
To view this discussion visit https://groups.google.com/d/msgid/lxnav-user-group/98417339-870a-48a1-8e81-8424967529a8n%40googlegroups.com.
Richard Pfiffner
May 26, 2025, 3:26:29 PMMay 26
to LXNav Soaring Glider Equipment User Discussion Group
LIFEPO4 batteries usually charge to 13.4v or a little higher. When you put load on them the go to 12.4 v very quickly and stay there until they are discharged an the BMS shuts them down at 10v.
Richard
K. R.
May 26, 2025, 4:24:39 PMMay 26
to LXNav Soaring Glider Equipment User Discussion Group
Huh? LiFePO4 charge to 14.6V and settle back to 13.6V without load. 12.4V is ~15% SoC.
Richard Pfiffner
May 26, 2025, 5:33:45 PMMay 26
to LXNav Soaring Glider Equipment User Discussion Group
LIFEPO4 Battery 10 AH
I have West Mountain Radio computer discharge CVA IV that produces a graph. Just to be exact If I charge to 13.6 v and discharge at 4 amps it goes somewhere to around 12.7v in about 3.5 minutes. And goes to 11.685 v in 150.08 minutes . It is now at the 10ah level and will shut down soon at 10 Volts.
Richard
K. R.
May 27, 2025, 1:08:49 AMMay 27
to LXNav Soaring Glider Equipment User Discussion Group
Interesting. Never considered recording the discharge curve when doing capacity tests. Will do next time.
Francois HERSEN
May 27, 2025, 2:17:53 AMMay 27
to LXNav Soaring Glider Equipment User Discussion Group
Now, I use the new Battery Monitor from LXNav and I may have in flight via bluetooth all the indications I need on my iPhone.
K. R.
May 27, 2025, 7:44:44 AMMay 27
to LXNav Soaring Glider Equipment User Discussion Group
Interesting idea. A 20$ unit for cars with the same features except LX-integration should do as well ;)
John DeRosa OHM Ω http://aviation.derosaweb.net
May 27, 2025, 8:41:05 AMMay 27
to LXNav Soaring Glider Equipment User Discussion Group
François,
Interesting technology. Thanks for sharing.
As I have two batteries in my glider I wondered if I could use two of these LXNav battery monitors tied to my phone's LXNav app at the same time?
It appears the answer is YES looking at the App's screen shot on the LXNav web page.
- John (OHM)
On Tuesday, May 27, 2025 at 1:17:53 AM UTC-5 Francois HERSEN wrote:
Now, I use the new Battery Monitor from LXNav and I may have in flight via bluetooth all the indications I need on my iPhone.
Le mardi 27 mai 2025 à 07:08:49 UTC+2, K. R. a écrit :
Francois HERSEN
May 28, 2025, 2:13:55 AMMay 28
to LXNav Soaring Glider Equipment User Discussion Group
Yes I use two devices for my two batteries in my ASH.
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