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A Different Battery Question



 
 
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  #11  
Old October 18th 19, 01:53 AM posted to rec.aviation.soaring
Dan Marotta
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Posts: 3,755
Default A Different Battery Question

I did pretty much what you said except for the recording and measuring
part.* My ClearNav and my Dynon D10a each have a volt meter displayed
and, though they had slightly different readings, they seemed to track
pretty well as I turned each device in turn.

For now, I'm gonna go with charging the lithium battery for a longer
period after the green light comes on, probably over night each time.

Thanks for all the good advice!

On 10/16/2019 1:50 PM, Charlie M. (UH & 002 owner/pilot) wrote:
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...).


--
Dan, 5J
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  #12  
Old October 18th 19, 01:56 AM posted to rec.aviation.soaring
Dan Marotta
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Posts: 3,755
Default A Different Battery Question

Hi Eric,

The two power resistors were in parallel for a total of 1.25 amps. Yes,
I should get around 10 amps (they sure got hot!) but I'll have to do the
measurement again to be sure, but I want to keep it charged up right now
to try a flight now that it's been on a charger for some time.

On 10/16/2019 2:01 PM, 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.


--
Dan, 5J
  #13  
Old October 18th 19, 01:59 AM posted to rec.aviation.soaring
Dan Marotta
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Posts: 3,755
Default A Different Battery Question

Really good advice, Tom.* I'll do that.

On 10/17/2019 6:26 PM, 2G wrote:
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


--
Dan, 5J
  #14  
Old October 18th 19, 07:36 AM posted to rec.aviation.soaring
2G
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Posts: 676
Default A Different Battery Question

On Thursday, October 17, 2019 at 5:59:58 PM UTC-7, Dan Marotta wrote:
Really good advice, Tom.* I'll do that.

On 10/17/2019 6:26 PM, 2G wrote:
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


--
Dan, 5J


It would also be helpful if got a smarter charger than the one you have. I use the Hitec X2 Pro:
https://hitecrcd.com/products/charge...harger/product
It will inform you how many AHr it put into the battery, which is a critical cross-check. It can also do a discharge test.
  #15  
Old October 18th 19, 09:44 AM posted to rec.aviation.soaring
krasw
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Posts: 520
Default A Different Battery Question

We charged LFP battery installed in glider using charger plug that feeds the battery via glider electrical system. We discovered that there was automatic breaker hidden in glider electrical system (DG DEI) that stole little bit of voltage. This caused charger to not charge battery to full. It seems that you cannot have automatic breakers between charger and battery.
  #16  
Old October 18th 19, 03:29 PM posted to rec.aviation.soaring
Tim Newport-Peace[_6_]
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Posts: 19
Default A Different Battery Question

At 08:44 18 October 2019, krasw wrote:
We charged LFP battery installed in glider using charger plug that feeds
th=
e battery via glider electrical system. We discovered that there was
automa=
tic breaker hidden in glider electrical system (DG DEI) that stole little
b=
it of voltage. This caused charger to not charge battery to full. It

seems
=
that you cannot have automatic breakers between charger and battery.

Whenever you put any device is series, expect to lose something. For
example with a series diode expect to lose about 0.5volt.

For this reason many radio manufacturers use a back-biased diode across the
supply and a series fuse. In this way no current passes through the diode
unless you cross-polarity the radio, in case it will be a short to blow the
fuse.




 




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