Battery question

Discussion in 'General Electronics Chat' started by Terp, Jun 23, 2008.

  1. Terp

    Thread Starter Active Member

    Jun 6, 2008
    32
    1
    Hi:

    I have a quick question on the concept of mAh of batteries -- to maker sure I understand it. The following website says that the CMDX-10 camera (in the link) http://www.rf-links.com/whats_new.htm draws 50mA at 6V. All that means is, if I were to power the camera with a 6V battery, it would draw 50mA current, right? Now, if I wanted to have the camera running for 1 hour, I would need a battery capacity of 50mAh, is that correct?

    I am considering this camera to be placed on my ornithopter.

    Thank you for your time.
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    Here is a page with all kinds of information on batteries.
    http://www.educypedia.be/electronics/componentbattery.htm

    If your camera uses 50 mA and runs 1 hour it consumes 50 mAh.
    An accu of 50 mAh will run low on that, you should use some overcapacity as the voltage will drop at the end.

    Greetings,
    Bertus
     
  3. Terp

    Thread Starter Active Member

    Jun 6, 2008
    32
    1
    When two batteries are connected in series, is the total capacity of the combo the sum of the capacities of each battery? So, if I use two 3V batteries each with 30mAh capacity, is the combo the same as a 6V battery with 60mAh?

    Thank-you for educypedia..........that site is great.
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Not quite. The two 3V batteries in series would provide 6V at 30mAh. The same two 3V batteries in parallel would provide 3V at 60mAh.

    Amps times Volts equals Watts. Watts times time equals energy. The batteries can supply as much energy as they contain, but no more than that.
     
  5. Ratch

    New Member

    Mar 20, 2007
    1,068
    3
    Terp,

    No, in a series connection, the same current will be present in both batteries, so the amp-hour rating will be the same as if each battery were in a separate circuit.

    In a parallel circuit, the amp-hour rating of the battery pack doubles because each battery ideally shares the current to be supplied. Ratch



    By the way, a 6 volt battery is simply several batteries in series and packaged together. A cell of the same type has a particular voltage determined by its chemical reaction, and that cannot be changed no matter how big or small you make the cell. An automotive battery is 6 lead-acid cells connected in series to make 12 volts. Ratch
     
  6. Terp

    Thread Starter Active Member

    Jun 6, 2008
    32
    1
    So in both cases (series and parallel), the energy would be double the value compared to when only 1 3V cell would be used to power the load. In series case, the net voltage would double, the current being the same as would be with 1 3V cell powering the load. In parallel case, the current would double (net voltage being 3V).
     
  7. Terp

    Thread Starter Active Member

    Jun 6, 2008
    32
    1
    Like a 7.4 volts lipo pack is two 3.7V lipo cells in series; also, 11.1 V lipo is 3 3.7V lipo cells in series.
     
  8. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    You are talking about very small battery cells. Look at their datasheet on a site like www.energizer.com. Little button battery cells have their mAh rated at a current of nearly nothing. A CR2012 3V coin cell has a capacity rating of 58mah when its current is only 0.1mA. Its capacity at 50mA might be for only a few seconds.
     
  9. Ratch

    New Member

    Mar 20, 2007
    1,068
    3
    Terp,

    Yes, two equal batteries contain twice the energy of one battery.

    Assuming the load does not change, in a two battery series arrangement, the voltage would double, the current would double, the energy would be expended 4 times faster than a single battery. The battery pack would last one-half as long.

    Assuming the load does not change, in a two battery parallel arrangement, if the batteries are balanced and share the load equally, each battery need only supply one-half the current, so the battery pack would last twice as long. Ratch
     
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