A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Soaring
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

A Different Battery Question



 
 
Thread Tools Display Modes
  #1  
Old October 16th 19, 05:48 PM posted to rec.aviation.soaring
Dan Marotta
external usenet poster
 
Posts: 3,755
Default A Different Battery Question

I've been using a 20 AH LiFePO4 battery as a backup in the Stemme. It's
portable and secured behind the passenger seat.* I charge it outside of
the aircraft.* When used, it is connected through an DPST switch (only
one half used) and switches the tail battery out of the system as it's
switched in.

The problem:* Even when fully charged it comes on line at around 11.4
volts or below and, if I key the radio, the radio display flashes and
the vario gives a Low Voltage warning.* When the tail battery is at 11.4
volts (it's an SLA battery), the radio works fine.

I've tested the lithium battery using a pair of 2.5 ohm power resistors
in parallel and measuring with a Watts Up power meter and it seems to
perform just fine, starting with voltage in the high 13s.* I ran it for
several hours that way, burning up about 15 amp hours without the
voltage ever dropping below the mid 12s.

Any ideas?* Everything seems to work just fine except for the low
voltage as measured at my ClearNav and at the Dynon D10a.* I'm using
good quality Tefzel wire of sufficient diameter, Power Pole connectors,
and the battery is properly fused.* I'm at a loss.
--
Dan, 5J
Ads
  #2  
Old October 16th 19, 06:41 PM posted to rec.aviation.soaring
Brian[_1_]
external usenet poster
 
Posts: 370
Default A Different Battery Question

You need to be checking voltage with a voltmeter in the airplane.
sounds like you have something in the circuit providing more resistance than you want.

Power up the aircraft on this battery and measure the voltage at the battery, it should be up at in the 12s like you expect. if it is not then you need to measure the current being pulled and possibly test with another battery. to see why it is different than you bench testing. Are you pulling more current than your bench testing? What devices are pulling that current?

If it is up in the 12s then measure at your onboard voltmeter and confirm it is reading correctly. You said it has been reading about 11.4. You should not be losing a full volt between the battery and your voltmeter. Then start checking the voltage before and after each component between the battery and your volt meter to see what the offending component or wire is. You may find it is a combination of wires or components that add up to the total voltage loss you are seeing.

Brian

  #3  
Old October 16th 19, 07:09 PM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 104
Default A Different Battery Question

How about divide and conquer?

Get the system in the condition you saw with more volts at the battery than the clearnav. (Maybe disconnect the batt and make sure the clearnav powers down just to make sure you have what you think you have.)

Split the path in half by measuring the voltage drop between the battery + terminal and the clearnav +power in. Then the batt- to clearnav power-.


Choose which part of the path has most of the voltage drop and pick an accessable point in the middle. Measure the two halves.

Then repeat with smaller and smaller parts of the path until you have found it.


  #4  
Old October 16th 19, 07:25 PM posted to rec.aviation.soaring
JS[_5_]
external usenet poster
 
Posts: 557
Default A Different Battery Question

Symptoms would indicate a bad connection or too light wire used.
Bad enough in such simple wiring, tragic on the neutral in 3-phase 400V. Seen enough of that film.
Jim
  #5  
Old October 16th 19, 08:50 PM posted to rec.aviation.soaring
Charlie M. (UH & 002 owner/pilot)
external usenet poster
 
Posts: 1,251
Default A Different Battery Question

Good thoughts posted thus far.....

My $0.02....with even an inexpensive DMM/DVM.....start at the "common buss" on/near the panel with all batteries fully charged.
Measure D.C. Voltage at the buss main input with a battery connected....
Switch things on, read voltage....write it down....
Key mic and do other load things...record voltage under load.
Repeat with the other battery.....
If the large battery shows a bigger voltage drop.....work through connections back towards battery with same test....see where the voltage drops lessens....in between good vs. bad/poor voltage drop is likely a poor or bad connection.

Could be a bad crimp, poor solder joint, loose/poor screw connection, maybe even small wire gage (although not likely unless waaayyyyy tiny...).
  #6  
Old October 16th 19, 09:01 PM posted to rec.aviation.soaring
Eric Greenwell[_4_]
external usenet poster
 
Posts: 1,206
Default A Different Battery Question

Dan Marotta wrote on 10/16/2019 9:48 AM:
I've been using a 20 AH LiFePO4 battery as a backup in the Stemme. It's portable
and secured behind the passenger seat.* I charge it outside of the aircraft.* When
used, it is connected through an DPST switch (only one half used) and switches the
tail battery out of the system as it's switched in.

The problem:* Even when fully charged it comes on line at around 11.4 volts or
below and, if I key the radio, the radio display flashes and the vario gives a Low
Voltage warning.* When the tail battery is at 11.4 volts (it's an SLA battery),
the radio works fine.

I've tested the lithium battery using a pair of 2.5 ohm power resistors in
parallel and measuring with a Watts Up power meter and it seems to perform just
fine, starting with voltage in the high 13s.* I ran it for several hours that way,
burning up about 15 amp hours without the voltage ever dropping below the mid 12s.

Any ideas?* Everything seems to work just fine except for the low voltage as
measured at my ClearNav and at the Dynon D10a.* I'm using good quality Tefzel wire
of sufficient diameter, Power Pole connectors, and the battery is properly fused.
I'm at a loss.


I'm guessing you did the test with the 2.5 ohm resistors in series (5 ohm total),
for about 2.5 amp draw. In parallel (1.25 ohms total) the draw would be 10 amps.

How much current is needed to run your instruments?

Disconnect the battery, short the connector, and select the backup battery with
your switch. Measure the resistance of the wiring with an ohmmeter on the (+) and
(-) of the 12 volt buss at the panel. It should read less than 0.5 ohms.

If that wiring (panel to battery box through the switch) is OK, look closely at
the connectors (glider side and battery side). Check the ohms for each lead from
battery post to battery side connector. It should less than 0.1 ohms (essentially
a short circuit). If the (+) lead is high, maybe the fuse is bad, too small, or
the wrong kind, or the fuse holder is faulty.

--
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

  #7  
Old October 16th 19, 10:38 PM posted to rec.aviation.soaring
Eric Greenwell[_2_]
external usenet poster
 
Posts: 12
Default A Different Battery Question

On Wednesday, October 16, 2019 at 1:01:35 PM UTC-7, Eric Greenwell wrote:
Dan Marotta wrote on 10/16/2019 9:48 AM:
I've been using a 20 AH LiFePO4 battery as a backup in the Stemme. It's portable
and secured behind the passenger seat.* I charge it outside of the aircraft.* When
used, it is connected through an DPST switch (only one half used) and switches the
tail battery out of the system as it's switched in.

The problem:* Even when fully charged it comes on line at around 11.4 volts or
below and, if I key the radio, the radio display flashes and the vario gives a Low
Voltage warning.* When the tail battery is at 11.4 volts (it's an SLA battery),
the radio works fine.

I've tested the lithium battery using a pair of 2.5 ohm power resistors in
parallel and measuring with a Watts Up power meter and it seems to perform just
fine, starting with voltage in the high 13s.* I ran it for several hours that way,
burning up about 15 amp hours without the voltage ever dropping below the mid 12s.

Any ideas?* Everything seems to work just fine except for the low voltage as
measured at my ClearNav and at the Dynon D10a.* I'm using good quality Tefzel wire
of sufficient diameter, Power Pole connectors, and the battery is properly fused.
I'm at a loss.


I'm guessing you did the test with the 2.5 ohm resistors in series (5 ohm total),
for about 2.5 amp draw. In parallel (1.25 ohms total) the draw would be 10 amps.

How much current is needed to run your instruments?

Disconnect the battery, short the connector, and select the backup battery with
your switch. Measure the resistance of the wiring with an ohmmeter on the (+) and
(-) of the 12 volt buss at the panel. It should read less than 0.5 ohms.

If that wiring (panel to battery box through the switch) is OK, look closely at
the connectors (glider side and battery side). Check the ohms for each lead from
battery post to battery side connector. It should less than 0.1 ohms (essentially
a short circuit). If the (+) lead is high, maybe the fuse is bad, too small, or
the wrong kind, or the fuse holder is faulty.


That should be "short the plane side connector"! I know Dan wouldn't short the battery side connector and waste fuse, but somebody might on their system...
  #9  
Old October 18th 19, 01:26 AM posted to rec.aviation.soaring
2G
external usenet poster
 
Posts: 676
Default A Different Battery Question

On Wednesday, October 16, 2019 at 5:57:18 PM UTC-7, Dan Marotta wrote:
Yes, that's good advice.* I was hoping to not have to remove the rear
console where the switches are located to do the troubleshooting.

Oh well, soaring season is coming to an end and wave season is not yet
in full swing.* I guess I'll need something to do in the interim.

On 10/16/2019 12:09 PM, wrote:
How about divide and conquer?

Get the system in the condition you saw with more volts at the battery than the clearnav. (Maybe disconnect the batt and make sure the clearnav powers down just to make sure you have what you think you have.)

Split the path in half by measuring the voltage drop between the battery + terminal and the clearnav +power in. Then the batt- to clearnav power-..


Choose which part of the path has most of the voltage drop and pick an accessable point in the middle. Measure the two halves.

Then repeat with smaller and smaller parts of the path until you have found it.



--
Dan, 5J


Losing over 2V is much more than can be explained by a high resistance connection (it would have to be multiple ohms). I think you have a bad ground connection for some reason, and the battery is finding a ground path thru another instrument. Measure the resistance to your a/c ground bus to the negative battery terminal. Do the same for the positive connection to the 12V bus.

Tom
  #10  
Old October 18th 19, 01:49 AM posted to rec.aviation.soaring
Dan Marotta
external usenet poster
 
Posts: 3,755
Default A Different Battery Question

Somewhere someone else mentioned that a LiFePo4 battery is not
necessarily fully charged just because the green light comes on on the
charger.* I left it hooked to the charger for 3 days, with a lamp timer
to cycle it off/on every three hours (I have other reasons for that
timing setup), and today I hooked it up in the Stemme and everything
seems to work just fine now.* I'm currently doing annual on our C-180
but, as soon as I have some free time, I'll fly the Stemme and see how
it works in flight

On 10/16/2019 12:25 PM, JS wrote:
Symptoms would indicate a bad connection or too light wire used.
Bad enough in such simple wiring, tragic on the neutral in 3-phase 400V. Seen enough of that film.
Jim


--
Dan, 5J
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
14v Battery Question. [email protected] Soaring 5 June 6th 15 02:40 AM
Garmin 396 battery question Paul kgyy Piloting 2 November 16th 07 06:13 PM
Battery Question mbremer216 Owning 7 October 6th 06 10:16 PM
Yet Another Battery Question P. Corbett Soaring 5 April 26th 06 02:22 AM
Battery Question [email protected] Soaring 19 September 15th 05 01:38 AM


All times are GMT +1. The time now is 07:00 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright 2004-2019 AviationBanter.
The comments are property of their posters.