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Aviation Forum / General / Soaring / July 2009Battery 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!) > Can anybody tell me what battery life you get in practice, when > running a transponder from a dedicated lead-acid battery, and what [quoted text clipped - 16 lines] > > 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 a.s 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 <remove_to_reply.abcon...@gmail.com> 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 [quoted text clipped - 4 lines] > -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 <remove_to_reply.abcon...@gmail.com> 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 [quoted text clipped - 4 lines] > > Darryl > 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 [quoted text clipped - 9 lines] > > > 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 > 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. 10.5 volts is "100% discharge" for a 12 volt battery; it would be 12.25 for a 14 volt system. Taking the 14 volt system to 10.5 volts puts the battery into deep discharge and potentially much shorter life, while getting very little extra amp hours from it. The shorter life of the over-discharged battery would quickly remove this small benefit. > 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". Dedicating a battery to the high-drain Terra might give you more hours than the current setup (the lower the current draw, the more amphours you can get from a battery), extend the life (years) of your batteries, and eliminate the need to switch batteries.  SignatureEric Greenwell - Washington State, USA * Change "netto" to "net" to email me directly * "Transponders in Sailplanes" http://tinyurl.com/y739x4 * Sections on Mode S, TPAS, ADS-B, Flarm, more * "A Guide to Self-launching Sailplane Operation" at www.motorglider.org 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 >> Can anybody tell me what battery life you get in practice, when >> running a transponder from a dedicated lead-acid battery, and what [quoted text clipped - 16 lines] >> >> Chris N. (In UK, but collecting data from anywhere that has it!) > For me (TERRA transponder with Nixie tubes display) - at most 4 hrs on > 14Ah battery before radio (yes) becomes totally unuseable. This is for [quoted text clipped - 30 lines] > > - 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. > > For me (TERRA transponder with Nixie tubes display) - at most 4 hrs on > > 14Ah battery before radio (yes) becomes totally unuseable. This is for [quoted text clipped - 37 lines] > 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. 8AH and 9AH 12v batteries in nominally the same form factor as 7AH (varies a bit by manufacturer) have become available for $18-$30. Last 8AH batteries I bought were $15. Guess I wonder why some are still using 7AH batteries. My LAK-12 has builtin boxes for two 12AH (or larger) batteries and room for insulation;^) Frank Whiteley > 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. Your setup sounds like it would have less than 1 amp draw, which would give almost 6 hours off a new 7 AH battery. Have you measured the actual draw? What is the battery voltage at the end of 3 hours? SignatureEric Greenwell - Washington State, USA * Change "netto" to "net" to email me directly * "Transponders in Sailplanes" http://tinyurl.com/y739x4 * Sections on Mode S, TPAS, ADS-B, Flarm, more * "A Guide to Self-launching Sailplane Operation" at www.motorglider.org > > 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 [quoted text clipped - 15 lines] > > * "A Guide to Self-launching Sailplane Operation" atwww.motorglider.org Not very scientific but I go until the dittle radio starts blinking then I switch to battery 2. Maybe I should look into where I am buying the batteries. They are power sonic ps1270f1 purchased at a local electronics store. >>> 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 [quoted text clipped - 5 lines] >> give almost 6 hours off a new 7 AH battery. Have you measured the actual >> draw? What is the battery voltage at the end of 3 hours? > Not very scientific but I go until the dittle radio starts blinking > then I switch to battery 2. Maybe I should look into where I am > buying the batteries. They are power sonic ps1270f1 purchased at a > local electronics store. But first, measure the current drain of your panel, and measure the capacity of your batteries. If you do get new batteries, fully charge them and measure their capacity, so you know you got fresh ones. SignatureEric Greenwell - Washington State, USA * Change "netto" to "net" to email me directly * "Transponders in Sailplanes" http://tinyurl.com/y739x4 * Sections on Mode S, TPAS, ADS-B, Flarm, more * "A Guide to Self-launching Sailplane Operation" at www.motorglider.org > Can anybody tell me what battery life you get in practice, when > running a transponder from a dedicated lead-acid battery, and what [quoted text clipped - 16 lines] > > Chris N. (In UK, but collecting data from anywhere that has it!) I run the following: - Becker 4401 175W - Becker 4201 Radio - Cambridge GPS-Nav - Cambridge L-Nav - EDW Micro-recorder - Compaq 1550 PDA I operate just outside the New York Class B airspace, so interrogation is essentially constant. All of this runs for a typical 5 hour flight off one 12V/12AH battery with voltage down to around 10.9-11V at time of landing. I have two of these batteries, so plenty of reserve for long flights. Operations include winter ridge runs at ambient temps of around 20F, but those are limited not by battery but by cold soaking of the pilot. P3 Thanks for all the answers so far. It is not specifically for me to fit in my glider, though I am considering it for when the European system will allow me to, but in connection with a paper I am writing, so I wanted a rough idea for the benefit of anyone with limited battery capability. Some UK potential users would be mainly lowish level thermal soaring, but there would be times when visiting wave sites and climbing to FL 195 or higher, sometimes for extended periods. Also, as more flying things get TCAS, there will be more interrogations. I thought gliders around Reno and similar high fliers might have some useful experience. Chris N. (In UK, but collecting data from anywhere that has it!) |
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