Battery worktime

Discussion in 'General Electronics Chat' started by Fatalfreak, Mar 25, 2011.

  1. Fatalfreak

    Thread Starter New Member

    Mar 25, 2011
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    Hi!I have a problem - my mp4 player's original battery died, and i tried to replace it, i took Nokia BL5C battery and soldered it to circuit, but unfortunately it last about 1 hour, meanwhile the volume is way to high! Earlier I listened music at 21-25 of 32, but now 13/32 is loud. Maybee someone has any ideas?I think i should reduce the current somehow, but how. P.S sorry for my english :p
     
  2. PackratKing

    Well-Known Member

    Jul 13, 2008
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    What is the specified voltage of your old /and/ different battery ? If much higher, that will explain the extra volume.........

    the unit itself, draws what current it needs from its normal OEM battery, based on volume set, and frequency playing. higher voltage drives it harder than it wants to be driven.
     
    Last edited: Mar 26, 2011
  3. SgtWookie

    Expert

    Jul 17, 2007
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    The Nokia BL5C battery appears to be rated for 3.7v.
    If the original was rated for 2.4v-3v, that would explain the difference in volume.
    You will most likely shorten the life of your MP4 player by using a battery voltage that is greater than what it was designed for.

    You should obtain the same type battery as the original for a replacement.
     
  4. Fatalfreak

    Thread Starter New Member

    Mar 25, 2011
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    I dont know, it was totally screwed, thats the main thing :/ I supose it was about 3-4 V , so I replaced it with 3,7 Nokia's. Ok I can agree with you, but if the voltage is to high, how may I reduce it?Some kind of connecting rezistor to battery?
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Why don't you use the manufacturer name and model number of the MP4 player to find a users' manual or users' guide online? It should tell you what the recommended replacement battery is.
     
  6. Fatalfreak

    Thread Starter New Member

    Mar 25, 2011
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    Because this is mp4 from China, well I am not so stupid as you think, If I could I would done it long time ago. That is why I seek for help here. DOES anyone know how to get aproximatly 2 V from 3,7 V battery, BECAUSE I don't know where to get 2V one.
     
  7. Audioguru

    New Member

    Dec 20, 2007
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    If you add a resistor in series with the battery then the voltage at the MP4 player will vary all over the place as its current changes with the music. The 3.7V battery is 4.2V when fully charged and the MP4 circuitry might be blown up by it when the music plays softly (because the current will be lower then there is less voltage dropped across the resistor).
     
  8. Fatalfreak

    Thread Starter New Member

    Mar 25, 2011
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    So no chance to get the necessary voltage safely? :/
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    Sorry if I seemed to be giving you a hard time; I was just trying to be helpful.

    I suggest the first thing you try to do is to figure out approximately what voltage your mp4 player actually requires. You could start by trying two "AA", "C", or "D" alkaline batteries in series to get about a 3v supply for your player. If it still seems louder than it was with your original battery, try a pair of NiCD or NiMH "AA", "C" or "D" batteries; which would output around 2.4v in series.

    It could be even easier to figure out if you had an adjustable low-voltage power supply, but I don't know if you have such a thing available.
     
  10. Audioguru

    New Member

    Dec 20, 2007
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    You and we don't even know what the battery voltage is supposed to be.
    You guessed 2V which is a big heavy lead-acid battery which is doubtful.
    It might be two 1.5V alkaline cells making 3.0V.
    It might be one 3V lithium coin cell.
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    You could also try using a diode (or two) in series with your 3.7v battery.
    A 1N400x series diode will drop around 0.7v to 0.8v with 10mA to 100mA current flow through it, so one diode would bring the voltage down to around 3.0v-3.1v from 3.7v.
     
  12. Fatalfreak

    Thread Starter New Member

    Mar 25, 2011
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    SgtWookie, don't apologise, It's ok ;) Ok if i figure out the voltage, how could i use a 3,7V battery?I still want to use it somehow, because AA's don't fit in player :D Ah and I haven't seen any 2-3 V lithium ones in stores.
     
  13. SgtWookie

    Expert

    Jul 17, 2007
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    Try using the 1N400x diode in series with the battery.
    Schottky diodes, like a 1N5817, would give you more "steps" as their forward voltage is considerably less than the 1N400x series diodes.

    Is there anything left of the original battery? Perhaps you could get the overall dimensions; LxWxH or diameter, and then figure out how many cells were in it. That way you might find the biggest battery that would fit in the space.
     
  14. Audioguru

    New Member

    Dec 20, 2007
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    A rechargeable lithium battery cell is 3.0V when dead and is 4.2V when fully charged. They are said to be "3.6V or 3.7V".

    We need to know which type of battery the MP4 player uses, the part number of its battery and find out if it is rechargeable. Where is the charging circuit?
     
  15. Fatalfreak

    Thread Starter New Member

    Mar 25, 2011
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    Oh idea with diodes sounds good :) I appreciate your help.
     
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