About battery supplying

Discussion in 'The Projects Forum' started by Lightfire, Apr 3, 2011.

  1. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
    21
    Hello,

    Okay. Here is the specification of my materials.

    Load: Two bulb 5 watts/12 volts (consuming 0.4166667 amperes) x 2 0.8333334 amperes
    Power Source: 12 volt lead-acid battery (12V/12AH) (Full Charged)

    Okay, as I said earlier I have a two bulb rated as 5 watts/12 volts so total all these two bulbs are consuming 0.8333334 amperes.

    I have a battery rated as 12 volts/12 amperes per hour (as I said earlier) so it can operate the two bulbs approximately 14.399999 hours. Isn't it?
    For safety reasons, I should only run the two bulbs approximately 7.1999995 hours (50% of 14.399999 hours).

    So, yes it can run. But may I ask if the two bulbs will stay just fine? I mean the bright of the two bulbs are just the same like what its brightness at the first.

    Also, the brightness of each two bulb are the same from each other?

    I hope, I am correct. If not, please correct me.

    Thank you.

    Postscript: What is the average mAh of a AA/1.5 battery?

    Thanks so much!!!
     
    Last edited: Apr 3, 2011
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    You are rapidly approaching the point where you will need to draw schematics. :D

    If the light bulbs are in parallel with each other, and they are the same kind of bulbs it will work. However, if one is new and the other old they may not look exactly the same.

    I have pulled bulbs from my car that were completely silvered inside, because the metal from the filament had evaporated off and coated the inside of the glass. These were very dim bulbs.

    As for a AA battery, google is your friend.

    http://en.wikipedia.org/wiki/AA_battery

    As it turns out, so is Wikipedia! :D
     
  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,795
    950
    "I have a battery rated as 12 volts/12 amperes per hour (as I said earlier) so it can operate the two bulbs approximately 14.399999 hours. Isn't it?
    For safety reasons, I should only run the two bulbs approximately 7.1999995 hours (50% of 14.399999 hours)."


    12 amps for one hour = 12Ah

    6 amps for two hours = 12Ah

    1 amp for twelve hours = 12 Ah

    Using it for 50% of its rated capacity is a good way to utilize it.

    Using it for only 30 or 40 percent of its capacity is the proper way to design for MAX. battery lifespan. With 50% and deeper discharges you will not get maximum lifespan, but will get maximum power per cycle from the battery.


    Small sealed batteries are either very good or very bad-depending on the manufacturer who made them. If you look for the cheapest you can find. you will get what you paid for. :)
     
  4. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    A 12Ah lead-acid battery is rated at a 20 hour rate which is 0.6A for 20 hours. It might provide 1A for 10 hours, 2A for 4 hours and 4A for 1.5 hours. It might not provide 12A for more than a couple of minutes.
     
  5. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
    21
    Yeah, I know that. :)
     
  6. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
    21
    Actually my battery was rated as 10-hr AH 12.

    I mean the 10-hr of my battery was 12.
     
  7. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
    21
    I am really bad at drawing. So, is there any programs that will help you draw a schematic? :p thank on what you have said to me. :p
     
  8. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Kermit's calculations are not accurate.

    I posted a graph showing a 12AH battery with different loads and time to discharge in one of your other threads. At that time, you were only talking about one 5W bulb as a load. Seems to me that 14 hours was the time for that load.

    However, you are now doubling the load, which will reduce the run time by more than half.

    What you need to understand is that the battery has an internal resistance. It's a fairly small resistance, but as the load increases, it makes more of a difference; power dissipation in the battery increases, so less power is available for the load.
     
  9. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
    21
    OK. :)

    Thanks!!!!
     
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