Battery life when running a transponder

Can anybody tell me what battery life you get in practice, when
running a transponder from a dedicated lead-acid battery, and what
size battery that is? And what model of transponder is it?

Has anybody measured the actual current drawn during operation, if so
what is it?

I am particularly interested in flights which include some high
altitude, cold ambient operation such as in parts of North America.

I am only interested in modern, solid state transponder operation, not
the older Mode C with a heater for the height encoder.

I have been given figures which suggest that a 7-amp-hour battery
would run one for 12 hours at surface ambient conditions, and I wonder
if anything like that is achievable in practice.

Thansk - Chris N.


Chris N. (In UK, but collecting data from anywhere that has it!)

On Jul 2, 9:21*am, Chris Nicholas wrote:
Can anybody tell me what battery life you get in practice, when
running a transponder from a dedicated lead-acid battery, and what
size battery that is? And what model of transponder is it?

Has anybody measured the actual current drawn during operation, if so
what is it?

I am particularly interested in flights which include some high
altitude, cold ambient operation such as in parts of North America.

I am only interested in modern, solid state transponder operation, not
the older Mode C with a heater for the height encoder.

I have been given figures which suggest that a 7-amp-hour battery
would run one for 12 hours at surface ambient conditions, and I wonder
if anything like that is achievable in practice.

Thansk - Chris N.

Chris N. (In UK, but collecting data from anywhere that has it!)


Many "modern" transponder installs in the USA will still have a heater
for the encoder. In the USA the Becker ATC-4401-1-175 Mode-C is pretty
common with an external encoder and the most popular encoder is an ACK
A-30 and that has a heater.

There is no single number that is meaningful to answer your question.
e.g. AGM batteries have significant temperature related effects. What
will work fine on one flight won't on another if the electrolyte
freezes. Most glider pilots however don't fly in those cold conditions
(but those who do need to be aware).

What problem are you trying to solve? Do you need to add a battery to
a glider and want to work out how big? For what flight profile? Are
you specifically worried about cold soaking?

This sort of question, prompted me a few years ago to give a talk on
glider batteries, the slides are at http://www.darrylramm.com/glider-batteries/
Hard to follow without speaker notes but you'll see some relevant
things. Do your own power budget, factor in your own battery temp and
aging factors and if nothing else take the manufacturers numbers for
the transponder (and encoder if separate). Or worse case use the
numbers for the Becker and encoder I have in the slides - those
manufacturer numbers are pretty good in practice. More recent
transponders will do better. I'd like to see actual measured numbers
for the Trig TT21. BTW the slides don't talk about circuit breaker of
fuses losses, I just did not have time and have no updated them. Just
don't choose really low value circuit breakers and you'll be fine.
Technical folks can look up the breaker actual specs and add those
into the budget.

So some wild ass numbers... Even a Becker ATC-4401-1-175 with ACK
A-30 encoder (with a nominal power draw around 0.49A) can give around
12 hours off a 7Ah battery at nominal conditions. A typical AGM
battery at 0C might be 15% down on it's spec (measured at 20C). Things
get "interesting" around -20 degrees where the electrolyte in an AGM
battery starts to freeze. The thermal mass and the somewhat natural
insulation of an AGM battery means the internal temp will take a while
to soak down. I had plans of inserting a thermometer into an AGM
battery but never did that. If that is a real concern on say long cold
wave flights you need to look at solar panels, battery insulation, pre-
heating batteries or different battery technology.



Darryl

Ive got a Garmin 320 with ACK 30 encoder that is ready to go in the
Cherokee. Perhaps tonight I will be able to get everything wired up and
check the current draw. Im expecting about 1.5 amps between the
transponder and encoder. That will drain my battery moderately fast, but
my "long" flights tend to only be about 3 or 4 hours anyway.


-Tony Condon
Cherokee II N373Y

On Jul 2, 11:30*am, Tony Condon
wrote:
Ive got a Garmin 320 with ACK 30 encoder that is ready to go in the
Cherokee. *Perhaps tonight I will be able to get everything wired up and
check the current draw. *Im expecting about 1.5 amps between the
transponder and encoder. *That will drain my battery moderately fast, but
my "long" flights tend to only be about 3 or 4 hours anyway.

-Tony Condon
Cherokee II N373Y

Remember measurement will be affected by the radar interrogation rate.
If it is not being interrogated on the ground you'll measure a lower
power draw than in practice.

Your excuse in future can be you had to land becasue the battery for
your transponder was going flat :-)

Darryl

On Jul 2, 11:30*am, Tony Condon
wrote:

...Perhaps tonight I will be able to get everything wired
up and check the current draw. *Im expecting about
1.5 amps between the transponder and encoder... *

Tony, if you get a chance please post the measured current draw here
on RAS.

If you'll recall, I suggested the GTX320 a while back on the basis of
having shoehorned one into my HP-18 panel. Eric Greenwell asked about
current draw, and I didn't have a good answer (I couldn't get a draw
value that I trusted) but I was pretty sure it was less than an amp
for the xpdr and only about 200 ma for the encoder. It'd be good to
see what your draw is, even if it is a base draw. If possible, maybe
see what the draw is during Ident when you know its transmitting.

Thanks again, Bob K.

Of course if you could put even a little insulating foam around the
battery, like layers of 1/4" foam core, it would help, as would
putting your extra sweater or shirt on top of it. As Darryl's photos
show, it's best to keep the chilled beer in another location.



The thermal mass and the somewhat natural
insulation of an AGM battery means the internal temp will take a while
to soak down. I had plans of inserting a thermometer into an AGM
battery but never did that. If that is a real concern on say long cold
wave flights you need to look at solar panels, battery insulation, pre-
heating batteries or different battery technology.

Darryl

On Jul 2, 2:14*pm, brianDG303 wrote:
Of course if you could put even a little insulating foam around the
battery, like layers of 1/4" foam core, it would help, as would
putting your extra sweater or shirt on top of it. As Darryl's photos
show, it's best to keep the chilled beer in another location.

The thermal mass and the somewhat natural
insulation of an AGM battery means the internal temp will take a while
to soak down. I had plans of inserting a thermometer into an AGM
battery but never did that. If that is a real concern on say long cold
wave flights you need to look at solar panels, battery insulation, pre-
heating batteries or different battery technology.

Darryl



Brian glad you noticed :-) That beer was drunk during an exhaustive
few days measuring battery performance.

And another comment to the original post. - even the Trig TT21
internal encoder has a heater as do most encoders. But again
temperature issues if any, may be the AGM battery behavior not the
encoder heater load. Some encoders however can have a high current
draw. Even with an ACK A-30 you can easily see the heater kick on. If
that is a problem then insulating the encoder could help. The typical
power consumption from that however is not worth worrying about. I
also would not really consider any encoder "solid state".

Just to make sure there is no confusion, the cavity tubes in older
(non-solid state) transponders have filaments or sometimes rarely
called "heaters" that drew high current (~amps) - entirely different
than the encoder heater.

Darryl

Operating a 12v with a 2v (both 8amp/hr or greater) piggybacked to
it , running a 302, PDA, borgelt 400, Becker radio, and an old Terra
transponder gives me about 6 hours before I hit 10.5 volts on the
"left-over" meter. I then switch to battery #2 and enjoy the ride.
Starting with 14v gives me the life boost I need. If I "dedicate" a
battery to just the transponder, I guess in excess of 8 hours. Wrap in
foam pack and it should outlast your Oxygen. How's that for "battery
life".
R

For me (TERRA transponder with Nixie tubes display) - at most 4 hrs on
14Ah battery before radio (yes) becomes totally unuseable. This is for
flights in the middle of summer at 11-18000ft. Added load from sources
other than transponder is about 500mA.

This year I added a 7Ah emergency battery so I can land without having
to fumble for my handheld which most likely also has a dead battery
.

Cheers,
Henryk Birecki


On Jul 2, 9:21*am, Chris Nicholas wrote:
Can anybody tell me what battery life you get in practice, when
running a transponder from a dedicated lead-acid battery, and what
size battery that is? And what model of transponder is it?

Has anybody measured the actual current drawn during operation, if so
what is it?

I am particularly interested in flights which include some high
altitude, cold ambient operation such as in parts of North America.

I am only interested in modern, solid state transponder operation, not
the older Mode C with a heater for the height encoder.

I have been given figures which suggest that a 7-amp-hour battery
would run one for 12 hours at surface ambient conditions, and I wonder
if anything like that is achievable in practice.

Thansk - Chris N.

Chris N. (In UK, but collecting data from anywhere that has it!)

On Jul 2, 8:38*pm, Henryk Birecki wrote:
For me (TERRA transponder with Nixie tubes display) - at most 4 hrs on
14Ah battery before radio (yes) becomes totally unuseable. This is for
flights in the middle of summer at 11-18000ft. Added load from sources
other than transponder is about 500mA.

This year I added a 7Ah emergency battery so I can land without having
to fumble for my handheld which most likely also has a dead battery
.

Cheers,
Henryk Birecki



On Jul 2, 9:21*am, Chris Nicholas wrote:
Can anybody tell me what battery life you get in practice, when
running a transponder from a dedicated lead-acid battery, and what
size battery that is? And what model of transponder is it?

Has anybody measured the actual current drawn during operation, if so
what is it?

I am particularly interested in flights which include some high
altitude, cold ambient operation such as in parts of North America.

I am only interested in modern, solid state transponder operation, not
the older Mode C with a heater for the height encoder.

I have been given figures which suggest that a 7-amp-hour battery
would run one for 12 hours at surface ambient conditions, and I wonder
if anything like that is achievable in practice.

Thansk - Chris N.

Chris N. (In UK, but collecting data from anywhere that has it!)- Hide quoted text -

- Show quoted text -

With a becker transponder, 302,303, Dittle radio, and pda 4700 I get
about 3 hours on one 7amp/hour battery. Most of the flight at 14k and
above. When I fly in congested areas altitude is lower but 3 hours
seems to be about all I get there also. Older batteries get less. I
also have a hook-up for PCAS but I was not using it this week (in
shop). The solar option on the glider would be nice as that helps.