what would happen if?

Discussion in 'The Projects Forum' started by andy73, Jul 20, 2008.

  1. andy73

    Thread Starter Member

    Sep 26, 2007
    10
    0
    hi all,

    im still getting my head round electronics and i have a question that i imagine is really simple but i just cant work it out.

    if i have two battey packs, the first (A) is 10.83v @ 6.6a and the second (B) is 43.3v @ 3.3a

    my question is what would happen is i connect both pos ends together and then both neg terminals?

    would i get 43.3v @ 6.6a, or would it just go bang!!

    i havent done this yet and wanted to ask someone with more experiance of this first, the idea of batteries going bang is not good

    cheers and sorry for the stupid question

    Andy73
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,652
    2,348
    Hello,

    When you connect the 43.3 Volt battery parallel to the 10.83 Volt battery,
    there will be a very large current flowing from the 43 volt battery to the 10 Volt battery
    that is only restricted by the internal resistance of the batteries.
    This will probably blow both batteries.

    Greetings,
    Bertus
     
  3. andy73

    Thread Starter Member

    Sep 26, 2007
    10
    0
    cheers Bertus,

    i though that somthing would go bang, i will make sure i dont do it...

    cheers
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,652
    2,348
    Hello,

    During the proces the batteries will get very hot and probably blow apart with hot pieces.
    This can be a little bit different depending on the type of batteries.

    Greetings,
    Bertus
     
  5. andy73

    Thread Starter Member

    Sep 26, 2007
    10
    0
    could i stop the current flow with a few diodes?
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    What is it that you're actually trying to do, Andy?
     
  7. bertus

    Administrator

    Apr 5, 2008
    15,652
    2,348
  8. andy73

    Thread Starter Member

    Sep 26, 2007
    10
    0
    hi SgtWookie,

    im making a model boat but i have 2 different batteries as discribed, and i want to put in a bigger motor. the new motor needs 36v @ 6a to run at top performance, i just wanted to see if i could get away with the batteries i have or should i just buy 3 x 12v @ 6ah bats and conect them in series?

    if i do the 3 bat way i will have to extend the hull a little, so i thought i would see if i could just conect the two i have together and run the motor.

    cheers
     
  9. andy73

    Thread Starter Member

    Sep 26, 2007
    10
    0
    cheers for the links Bertus
     
  10. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    You will need the three 12V batteries in series. Either that or use some form of voltage regulation and the single 43.3V battery. The 10V battery should be stored away for some other project in the future.
     
  11. andy73

    Thread Starter Member

    Sep 26, 2007
    10
    0
    cool ok cheers for the info, just thought id see if it was possible
     
  12. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Even with a regulator, the 43v battery can only supply 3.3A, and your motor requires 6A @ 36V.

    I agree with the recommendation that you will need to go with three 12V batteries.
     
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