Bryan Wood said:After the ELT has been run for a cumulative 1 hour all cells must be replaced. Otherwise you can leave them in until their expiration.
c177tx said:Here is a link to an interesting article that help explain the ELT battery replacement issue. The one thing is that the 50% life of the battery requires that that if the batteries are good for say 4 years then they will need to be replaced every 2 years. so if the experation date is say 2011 then they will need to be replaced in 2009.
http://www.avionicswest.com/articles/eltupdate.htm
The other definition of "useful life", often used in the electronics world is "shelf life".johnp said:......
1. it seems self-evident to me that the "useful life" of a battery is the length of time that that battery can be used to operate the piece of equipment, in this case an elt. e.g., if the battery has a capacity of 3 amp/hours and the elt draws 300 ma, then the useful life of that battery would be 10 hours of use (simplification should be adequate for purposes of the logic.)
........
az_gila said:The other definition of "useful life", often used in the electronics world is "shelf life".
All batteries self discharge (decay?) to a certain extent and loose capacity just sitting on the shelf.
This is essentially what happens to your ELT battery when it sits there in the back of your plane doing nothing.... You need to replace the battery before it looses 50% of it's capacity...
I bet the life spans are set conservatively (as they should be) and are probably set to a worse case (again, a guess, but I bet self discharge is higher when the battery is hot).
gil A
The amount of time a cell or battery will retain a specified percent of its rated capacity, typically under ambient storage conditions.
Voltage drop under a no-load condition is not a good indicator of capacity.gasman said:...When the voltage drops to 90% or I reach the date printed on the battery, I will change them. Or they WILL be changed after one hour of use.
I had a 1% drop in voltage in two years.....
John ... that makes sense.johnp said:my conclusion is that the shelf-life is a non-issue, and is handled by the fact the by the expiration date, vastly more than 50 percent of the rated capacity remains (inductively reasoned by the samples i saw -- it's not easy to find shelf-life specs on the web. they tell you the number of years, but not the percentage of rated capacity remaining in many cases.) i think my conclusion is reasonable and supportable. ymmv
regards
osxuser said:Ok, here is a different perspective. In older ELT's that used the same type of batteries, except packaged in to battery PACKs that were infinitely more expensive, they had to be replaced every two years. I therefore replace the cheep ones every two years too, and use them for other things afterwards. And ELT, while not a promise of rescue, isn't something I pinch penny's on.
n5lp said:Voltage drop under a no-load condition is not a good indicator of capacity.
When I was in the service, we kept spare batteries in the frig whenever possible. I was told that the battery shelf life was greatly extended. I continue to do this myself now.az_gila said:I bet the life spans are set conservatively (as they should be) and are probably set to a worse case (again, a guess, but I bet self discharge is higher when the battery is hot).
gil A
I would be more concerned about how my insurance company might respond to a claim if they thought that I had not maintained my airplane correctly.frankh said:That a 121.5 MHZ is next to useless in actually getting you rescued then spending the money on replacing batteries is a waste of money.
I plane to keep the duracells in there as long as possible and take my PLB with me on trips that take me away from civilisation.
if the engine quits, PLB gets activated...step one. Everything else is secondary apart from keeping the sunny side up.
When 406 units get more reasonably priced I will upgrade and then pay more attention to battery life.
Frank
IMHO the issue would be if you had a friend with you and he/she died as a result of not getting help in time AND "they" found the batteries were not replaced at the appropriate time. I'm not an attorney but that might constitute negligent homicide. (?)kentb said:I would be more concerned about how my insurance company might respond to a claim if they thought that I had not maintained my airplane correctly.
Kent
George.. the 50% life is built into the "expiration date" on the cells, and is a lot longer than 2 years. ACK quotes 95% remaining after two years...gmcjetpilot said:Annual Duracell "D" bat changes = good idea
The FAR's are clear (as mud) but the folks who say change the Duracell D's at 50% of their shelf-life are correct. I use to think it was annual and that's not corrects. All this assumes you know the mfg and exp date to calculate 50%.
What if the the exp date is only 16 months out? Does that mean you only get 8 months out of it? I recall Duracell D's have a typ shelf life of 2 years, so the 50% shelf life is NOT an advantage, thus go on 1 year or expiration date, what ever is shorter. I think the Duracell "Ultra" is approved as well, so may be that's 6 year shelf? Than in theory I guess you could get 3 years out of it. Check the package.
That a 121.5 MHZ is next to useless in actually getting you rescued then spending the money on replacing batteries is a waste of money.
I plane to keep the duracells in there as long as possible and take my PLB with me on trips that take me away from civilisation.
if the engine quits, PLB gets activated...step one. Everything else is secondary apart from keeping the sunny side up.
When 406 units get more reasonably priced I will upgrade and then pay more attention to battery life.
Frank
Replacement of the battery pack is nearly $300. Has anyone just replaced the battery cells? They are just D Cell size Lithium batteries with solder tabs.
I'm sure someone will debate me on this but before you do please cite regulatory references backing up any claims. Since the airplane is experimental one can experiment with ELT batteries. There are no TSO requirements for any parts in an aircraft certified in the experimental amateur built category.
I have discovered in the last few years that Duracell batteries seem to leak at a much higher rate than other brands. This timing seems to relate to the shift to China manufacturing.
I no longer use Duracells. (Personal choice)
I’m not a lawyer, but I know that in legal jargon your question revolves around ‘strict liability’. e.g., you have a contract with the insurance company. Usually that contract requires you to maintain and inspect your airplane in accordance with the FARs. You have an accident that has nothing to do with the ELT battery, but after the accident it’s noted that the battery is beyond its expiration date. Can the insurance company deny coverage because you violated the contract? In some states, yes. This is called strict liability. But in other states, no. They require the expired battery to be relevant to the accident.If true, the battery being unairworthy could be cited by the insurance company as grounds to deny coverage in the even of a claim? I'm not a lawyer. Does that make sense?
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Please read §91.207.
ELTs and Transponders must meet TSO for Experimental Amateur-Built Aircraft.
Same for the PLBs - I have one where the battery replacement cost is over half way to the price of a new unit.... This discussion is again relevant for the higher prices, assuming that the cells can be located at a reasonable price, legality not withstanding.
Please read §91.207.
ELTs and Transponders must meet TSO for Experimental Amateur-Built Aircraft.
I put Duracells in my ELT and so far no one has shown up from the FAA to see if it works.
... I always say nuthin' happens until after the accident.
This raises a related question... uAvionix' TailBeaconX is a Mode S transponder that fits all in one unit. There is no external antenna connector on it. So how does an avionix shop validate that it meets transmit power requirements? Or anything else that would normally be done by plugging the test equipment into the antenna port?If you replace the authorized ELT batteries with Duracell batteries, how do you prove the ELT still operates within the required standards? Same with a transponder, GPS, etc. If you build your own transponder, how do you prove it operates within the required standards?
There is transponder test equipment available that is calibrated based on placing it's receiver antenna a specified distance from the transponder antenna. All of the parameters required for a 14 cfr 91.413 testThis raises a related question... uAvionix' TailBeaconX is a Mode S transponder that fits all in one unit. There is no external antenna connector on it. So how does an avionix shop validate that it meets transmit power requirements? Or anything else that would normally be done by plugging the test equipment into the antenna port?