Old EPIRB battery

Discussion in 'General Electronics Chat' started by axeman22, Oct 24, 2012.

  1. axeman22

    Thread Starter Active Member

    Jun 8, 2009
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    hey guys...

    I have an OLD EPIRB.. a KTi RB3 ( http://www.trailjournals.com/images/gear/tjgear_7052_030708_30870.jpg )

    it has a battery pack in it which consists of two x 3V Lithium Sub C cells in series wiring. On the negative of cell one there is a a .22 Ohm 10% resistor going to the negative lead of the connector, on the positive of cell two there is also a .22 Ohm 10% resistor then off the the positive in the connector.

    I'm trying to understand why these .22 Ohm R's would be there... any ideas..?

    could it be a cheap voltage reg if the current draw is a known quantity ..?

    why two x .22 Ohm - you could just put one x .44Ohm R as it is a series circuit ..?

    aside from this.. I am thinking of making up a lead to power this from the car or motorbike.. 12Volts in.. could I just use a LM7806 for example ..?
     
  2. JMW

    Member

    Nov 21, 2011
    88
    8
    Triggering an EPIRB, even accidentally can result in a substantial fine. That being said, these are repairable. There are at least 2 levels, batteries can be replaced by a qualified shop, otherwise it must go to a depot or possibly the factory. I've never found a schematic anywhere.
    The early ones transmitted on VHF Marine 15 156.775FM + Aircraft 121.xx + frequency that will reach a LEO satellite. Newer versions also send a digital ID
     
  3. axeman22

    Thread Starter Active Member

    Jun 8, 2009
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    Hi JMW - thanks for the reply however it bares no relevance at all to my question.

    I'm fully aware of the implications of triggering one. I'm not looking to go to a shop, I will do it myself. I'm not looking at all for anything related to the newer 406Mhz COSPAS/SARSAT ones - just this old style 121.5/243 Mhz one.

    This really is just an electronics question - it matters not that we're talking about an EPIRB.

    anyone else have any ideas..?
     
  4. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Why would you take a emergency device and hook it to a car or motorcycle?

    Cars put out a huge amount of electrical noise, and I'll bet they are nothing compared to a motorcycle. And electronics connected to a car needs to be specifically designed for that purpose.

    Do yourself and the coast guard a favor, drill a hole through the think and throw it in the trash.
     
  5. axeman22

    Thread Starter Active Member

    Jun 8, 2009
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    I'm in Australia guys.. no coast guard here.

    lets forget it's an EPIRB.. and forget it's going on a bike.. lets just think of it as a 12Volt source (plain old Lead Acid battery) ..

    if I need to use it, the motorbike/car/whatever will not be running - so it's just a pure simple 12Vdc source.

    I have done my research with this device - given that I have a spot messenger also.. this will be perfect.
     
  6. nkosinathizvimba

    New Member

    Aug 24, 2012
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    When old battery shipping your EPIRB for battery replacement, please gently remove the antenna by unscrewing at the base and rubber band or tape it to the body of the EPIRB.
     
  7. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    The resistors are present for the built in charge control circuitry of the Lithium battery. It is used to get a voltage FOR EACH CELL in the pack. The batteries cannot be allowed to become unbalanced while charging or in discharge. Serious problems can occur with lithium batteries. safety circuits are included in these packs for a very good reason.

    Personally, I hate them and will do almost anything to avoid using them. (There are lithium types that are not nearly so dangerous)
     
  8. axeman22

    Thread Starter Active Member

    Jun 8, 2009
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    There are no charging on these batteries at all..

    Can someone delete this thread - clearly, no one on here has any idea or ability to understand the actual question :-(


     
  9. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Nice attitude!

    :)

    Instead of giving the chemistry of the battery you have, you complain about the answers you get. Clarity in questioning gives one access to illuminating answers.

    100 x 100 dpi picture links, and no schematic gives one answers commensurate with that level of information.


    Now let's hear more from you. Please!
     
    Last edited: Oct 27, 2012
  10. bertus

    Administrator

    Apr 5, 2008
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  11. debe

    Well-Known Member

    Sep 21, 2010
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    184
    I would suspect the 2 resistors are there to act as fuses if there was a short in the unit. As lithium batterys are capable of quite large currents & over heating. Why not just replace the batterys? they do have a very long life.
     
  12. axeman22

    Thread Starter Active Member

    Jun 8, 2009
    53
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    Far out.. Is it really that hard to understand the actual question I asked...really, I'm assuming that are smart and intellectual people on here, with a solid understanding of electronics. There are many boards where people just post absolute shxt.. Because they want to get their number of posts status up.. Is this the case here.? Seems so..

    Is it because its full of Americans, and you're defended by your own desire to listen to yourself..?

    The Internet links from bertus,,, useless. Yes I search the net. This is what forums are all about, like a coffee club..at a coffee club you ask questions, share ideas.. You don't spend early morning searching for answers on the net then just seeking ratification over coffee...

    Just to clarify,
    - I'm not searching for replacement batteries.
    - I don't need a lecture on my use case and or the coastguard etc.
    - I don't need a lecture on how to dispose lithium batteries properly etc...or where to buy new ones etc.
    - the circuit does never recharge the batteries so the resistors have nothing to do with charging, balancing etc

    So..excuse my anger, but, as a last try...if there is anyone on this board, who possesses deep within their soul, the ability and intellect to understand the original question, and has a solid understanding of circuits and component placement rationale(probably an electronics engineer) then please post..away. Previous posters on this thread, I'm clearly not referring to you.

    Said with a smile..but, sheesh guys...are you just winding me up, or genuinly stupid..! :)
     
  13. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Wow you are going to get a lot of help around here with that attitude. :rolleyes:

    How do you insult someone "with a smile"?


    And you do realize that there are people from all over the world both asking and answering questions on this forum. Some trying to answer your questions might very well be from your own country (debe is from your country) so you just insulted them too. Good job.
     
  14. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    if they do not comprise a portion of a charging circuit

    if they do not belong to any other component or portions of a circuit that you are not aware of, or have not told us about.

    if you do not need any instructions on how to use that type of battery

    Current limiting is all they are capable of. too much current and they 'smoke'.

    Contact the manufacturer for further details of the design engineers line of reasoning for including them.
     
  15. axeman22

    Thread Starter Active Member

    Jun 8, 2009
    53
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    Thanks kermit...

    I was thinking perhaps that...but the fact that the is a resistor on each leg miffed me. If I was the engineer I would just put one, of the right value on one leg, less parts , simpler, cheaper.. ?

    Thoughts in why they'd use two...surely it can't be as simple as ..well we had a draw full... :) :)
     
  16. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Actually it can be that simple.

    .44 is not a standard value, but I believe .22 is.

    :)
     
  17. axeman22

    Thread Starter Active Member

    Jun 8, 2009
    53
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    You're totally making sense.. Thought I thought the circuit would limit the current, ie it'd only use what it needed, hence being limiting units own sense.?

    It does transmit fairly high power...5watts I believe..so perhaps they built it, then kept playing with the resistor value to ring it back to 5watts..all that is required, and lengthen battery life..perhaps..?

    But then the voltage drop over then would affect to voltage available to the circuit..but, I guess the circuit could also just be a lower voltage one, 3volts etc..so plenty of room to move, or by varying the input voltage, as it is a transmitter circuit, this could effectively reduce the power also..?

    Perhaps I should just call the engineers..! :)

    Thanks kermit for injecting some solid value to my thread, greatly appreciated.
     
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