Lithium battery enegy

Discussion in 'The Projects Forum' started by meththas, Mar 16, 2012.

  1. meththas

    Thread Starter New Member

    Feb 26, 2010
    16
    0
    Hi All,

    I am trying to decide between two voltages of a battery that gives the same Ah output. The first is 14.8V and other a 11.1V battery both giving 4.4Ah (Lithium).

    If I use a lower voltage how will that affect the energy and cycle life of the battery?

    Currently I expect the 14.8V 4.4Ah battery to cycle through ~200 cycles of my instrument. I was told I can use a lower voltage without much affect on this number... but I don't know why. Can anyone confirm and explain this to me please.

    Thank you in advance.
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,151
    3,058
    The higher voltage has more power, since power is voltage x current. But your load may not benefit if it has a linear voltage regulator inside it, which simply burns off excess voltage as heat. So, more info is needed to answer the question.
     
  3. ishaan3731

    Member

    Jun 23, 2011
    43
    1
    please define the problem in a precise manner ie. what kind of circuit you are using that supply for.... and other important information etc. It all depends from application to application ....... Just for eg when making a robot.... u need 12 volts for the motor ....but the actual requirments to get maximum rpm from motor is the availibilty of current of around 1A.......even if ur operating the motor at 9V's....... So alll depends on ur application!!!!!
     
  4. wmodavis

    Well-Known Member

    Oct 23, 2010
    737
    150
    The battery's energy or power is, as wayneh says, equal to voltage times current and is in no way dependent on "what kind of circuit you are using". That simply has nothing to do with your question. It does NOT depend on your application!

    14.4 x 4.4 = 65.12 watt-hours of energy
    11.1 x 4.4 = 48.84 watt-hours of energy
    65.12 - 48.84 = 16.28 watt-hours more energy in the 14.4 volt battery.

    Of course that assumes a fully charged battery capable of its full rated capacity.
     
  5. meththas

    Thread Starter New Member

    Feb 26, 2010
    16
    0
    Thanks for all the replies.

    For all those asking about the application,

    the battery will be supplying 2 different voltage rails 5V and 3.3V that has a mirocontroller, sensor and a LCD connected to it. 5V will take around 200mA as will the 3.3V.

    The instrument will be powered up for around 60seconds at a time while it takes some readings, analyses and displays.

    I am using switch modes to bring the voltage down to the level required.

    Using the 14.8V seems a bit wasteful to me as I do not need it to be that high. Hence why I wouldnt mind to move to the 11.1V battery.
     
  6. #12

    Expert

    Nov 30, 2010
    16,341
    6,824
    The 14.8 V supply "wastefulness" is almost eliminated by using a switchmode controller. The best thing about switchmode controllers is that they waste very little energy as heat...unlike a linear regulator. I wouldn't change from 14.8 to 11.1V if it only cost a single dollar, as long as a switchmode controller was in charge.
     
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