Need 12VDC Battery for my project

Discussion in 'The Projects Forum' started by mpcotuong, Apr 12, 2011.

  1. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    Hi All,

    I have a project using 12VDC for run the Motor and would like to use the batterry instead wall adapter. Do you know any batterry of 12VDC 1 or 2 A?

    Thanks,
    Kevin
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,770
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    And how long do you need this battery to run for?
     
  3. russpatterson

    Member

    Feb 1, 2010
    351
    16
    You need to figure out how long you want it to run at a given current output (as pointed out above). However you can get a good price for 12V SLA's here: http://www.allelectronics.com/make-...atteries-Rechargeable/Sealed-Lead-Acid/1.html

    These are not the best batteries you can buy, but I've had good luck with them as long as you don't overcharge or over-discharge (lower than 10V). Once that happens they become large capacitors. I assume that quality control is low so performance from battery to battery may differ. At any rate make sure that you're not going to let the battery discharge to less than 10V, 12V would be better for the life of the battery. Don't charge it more than 13.8-14 volts.

    What's the motor do? How are you going to charge the battery?
     
  4. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    I need batterry long at least a month for my project. Do you know any battery can run up to a month?

    Thanks,

    Kevin
     
  5. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,792
    945
    Think of the battery AMP HOURS as money and the Battery is the Bank.

    Your motor will use 1 or 2 amps(money) every hour.

    How much money must the bank have to keep your motor running for ONE MONTH?

    You will need many LARGE batteries in parallel to run the motor for one month. Then you will need a very large generator(several Kilowatts) to recharge them in a reasonable amount of time.
     
  6. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    Thanks, for your input. Do you have model battery for recommend?

    Kevin
     
  7. gerty

    AAC Fanatic!

    Aug 30, 2007
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    Is this going to run continously for a month?
    Is it going to cycle on/off at all, if so , how long is it going to be on?
     
  8. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    Yes, Gerty. I need to connect my circuit to battery all the time. The Motor will run 20 second a time and 20 time a day. Can any battery long to a moth?

    Thanks,
    kevin
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    Motors draw considerably more current than they are rated for when they are first starting up; perhaps 7 to 10 times as much current. As they get up to speed, the current draw reduces.

    What is your motor for? A bilge pump on a boat, maybe?
     
  10. mpcotuong

    Thread Starter Member

    Aug 26, 2010
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    The 12DC motor to lift the object of two pound.

    Thanks,
    Kevin
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    OK, so you have about 6 minutes and 40 seconds' worth of run time per day, maybe 1/10th of that at stall current - however much that turns out to be - so for a 30-day month, about 200 minutes of operation, or 3-1/3 hours of operation, of a 2A load.

    I'll suggest that you need a battery of around 10 to 12AH rating. SLA (sealed lead-acid), VRLA (Valve Regulated Lead-Acid), AGM (Absorbent Glass Mat) are types of batteries that you can use.

    The greater the AH rating of your battery, the longer it will last in use. If you allow the battery to become discharged more than about 1/3 maximum, its' service life will decrease. If you discharge it more than 50%, its' life will be much shorter. If you discharge it completely, it will have a VERY short service life.
     
  12. mpcotuong

    Thread Starter Member

    Aug 26, 2010
    170
    0
    Hi SgtWookie

    Is the 10 to 12AH mean AMP? Will it too much or over current of my circuit? Will battery dischagre once it connect all the time to the circuit?


    Thnaks,

    Kevin
     
  13. Adjuster

    Well-Known Member

    Dec 26, 2010
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    The current actually drawn, and how this varies with time will depend on your circuit. Connecting a battery with a big Ah rating does not force a big current to flow, although larger capacity batteries will be able to deliver higher currents for longer if the circuit demands them.

    The Ah (Ampere hour) rating of a battery tells you approximately the Amps times hours you can expect to get out of a fully-charged battery until it needs recharging. The Ah rating really only applies at some specified rate of discharge, so a battery of 40Ah capacity at a 10 hour rate could be expected to supply 4A for 10 hours. Generally the capacity is less for higher current drain, so for instance if you tried to draw 8A from the same battery, it would not last as long as 5 hours, but at 2A it could last a bit more than 20 hours.
     
  14. mpcotuong

    Thread Starter Member

    Aug 26, 2010
    170
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    Hi Adjuster,

    Thanks, for your explain. It mean I need high AH will last longer right?

    Do you have any model fro recomendation?

    Kevin
     
  15. mpcotuong

    Thread Starter Member

    Aug 26, 2010
    170
    0
    How Do I know that the battery will need charge and the circuit stop working? Do I need some logic to mention that baterry need re charge before it out power?

    Thanks,
    Kevin
     
  16. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Check it with a meter, 12.3V should be about 75% discharged.
     
  17. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Yes.

    Roughly 10 to 12AH or larger SLA, VRLA, or AGM battery.

    Since we do not know where in the world you are (you have not put your Location in your profile) it would be pointless for us to suggest an exact model, as you may not be able to buy it where you are.
     
  18. mpcotuong

    Thread Starter Member

    Aug 26, 2010
    170
    0
    What is logic circuit to display LED to tell the Battery need to recharge?

    I am in california

    Thanks,

    Kevin
     
  19. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    A simple-low current battery monitor can be made from a V ref. & a comparator, bottom one, with a red LED as indicator. Battery drain should be about 500μA. With an input of 12.2V, adjust 10k pot so that LED just turns on.
     
  20. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    In the other part of the circuit, where does the input signal, pin 3 of LM393, come from? And is it a positive going sig. or neg, & how wide is it?
     
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