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Thread: How to make an external battery pack?

  1. #21
    Member eawtan's Avatar
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    Default Re: How to make an external battery pack?

    Quote Originally Posted by Max 2.8
    So as long as the thing I do up supplies a 2.5A thing, It should work for the rest of my gadget lah.

    I think I give up.....just get the 4 AA thing solder some wires and jack can already lah.
    Yes... if u fix up with just 4 AA pack to the connecter, be careful of the polarity (+ and -).

  2. #22
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    Default Re: How to make an external battery pack?

    ok...thanks! see you again for the next ir shoot

  3. #23

    Default Re: How to make an external battery pack?

    Quote Originally Posted by eawtan
    OK, I try to put it simply.
    There is a commonly used chip part number - 7805. (Avaliable at simlim tower)
    Input requirement is 7.2V to around 15V, output of this chip is a nice constant 5V output.
    Issues - this chip can only give a max of 1A at 5V (if your equipment requires more than 1A current, then this chip will shutdown) . When input drops to below 7.2V it may still working. Due to the conversion, some power is wasted.

    Can understand ?
    What eawtan means is this 7805 regulator chip in the pic below. You need a 8 battery pack to provide about 9.6V to the chip and it will provide a regulated output of 5V.




    From http://www.tkk.fi/Misc/Electronics/circuits/psu_5v.html

    Do remember to add 2 capacitors to prevent voltage spikes.

    Alternatively you can get a variable voltage regulator circuit like this.....
    http://www.futurekit.com/detail.php?id=118

    Its available in the yellow packs of circuits at the shops at Sim Lim tower or SLS basement. You need to solder it though.

    EngHong

    O.T.
    eawtan, are u an elect engineer?

  4. #24
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    Default Re: How to make an external battery pack?

    So I just get this thing from SIm Lim TOwer, solder them together and input with 8 pcs of 1.2V AA batteries(Sanyo) and the output will be 5V?

    Ok...if my X-drive last 2.5hrs with its built-in battery, how long will this thing of your works?

  5. #25

    Default Re: How to make an external battery pack?

    That depends on your device and your batteries. The circuit only regulates the voltage. It takes some current but not alot. Its your x-drive(load) which sucks the current from your batteries and when your current on your batts runs low, your device stops working.

    So you have to compare with the mAh of battery of your x-drive and that of your rechargable AAs.

  6. #26
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    Default Re: How to make an external battery pack?

    wah cheem again...

    How much A does 8 Sanyo2300nimh batteries have?

    the x drive battery says 3.7v 1800mah. but the input hole says 5v 2.5A?

    ?????
    Last edited by TrailsofLife; 18th October 2005 at 05:37 PM.

  7. #27
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    Default Re: How to make an external battery pack?

    actually, do you add up the total of the batteries'mAH? I mean, 1 2300nimh battery is min 1.2V 2100mAh according to the battery, if I put 8 together, is it 9.6V 16800mAh?

  8. #28

    Default Re: How to make an external battery pack?

    Quote Originally Posted by Max 2.8
    wah cheem again...

    How much A does 8 Sanyo2300nimh batteries have?

    the x drive battery says 3.7v 1800mah. but the input hole says 5v 2.5A?

    ?????
    The input hole is for your AC adaptor which should give a 5V 2.5A output to your x-drive. But your battery is a 3.7v 1800mAh battery.

    actually, do you add up the total of the batteries'mAH? I mean, 1 2300nimh battery is min 1.2V 2100mAh according to the battery, if I put 8 together, is it 9.6V 16800mAh?
    Cannot count like that cos your AA batteries is in series so its still 2100mAH.

    Its counted using power. power(W) = current(I) x voltage(v) so for 8sanyo batteries = 9.6v x 2100mAh = 20.16W

    For your x-drive battery, its 3.7v x 1800mAH = 6.66 W

    Meaning theoratically your battery pack should last at least 3 times your x-drive battery. But this is only simple maths. In reality, there are many more factors comming in which results in you getting less, so take it that at least 2x longer. Best way to know, try it out.

    EngHong

  9. #29
    Member eawtan's Avatar
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    Default Re: How to make an external battery pack?

    Quote Originally Posted by Max 2.8
    actually, do you add up the total of the batteries'mAH? I mean, 1 2300nimh battery is min 1.2V 2100mAh according to the battery, if I put 8 together, is it 9.6V 16800mAh?
    Nope. Voltage increase, but mah remains. A simply calc,
    original - 3.7 V 1800mAh gives ~6.66Wh (?)
    with 8x 2300mAh gives ~22Wh
    so you should get ~3.5X longer life.

  10. #30
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    Default Re: How to make an external battery pack?

    So its quite alright...meaning I get almost 10 hrs more lah....

    Am I right to say I get that board you show me, attach a 8X battery case to the input...It should give me 8-10hrs of battery supply?

    This is interesting....where you buy the board and those little stuff? How much?
    Last edited by TrailsofLife; 18th October 2005 at 07:00 PM.

  11. #31
    Senior Member afbug's Avatar
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    Default Re: How to make an external battery pack?

    OT a bit. Sorry to hijack.

    BTW is there a way to protect wires? eg a earphone wire. Something like a cable sleeve? How do i go about doing it? Any idea?

  12. #32
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    Default Re: How to make an external battery pack?

    Protect earphones wires? neccessary meh?

  13. #33
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    Default Re: How to make an external battery pack?

    Quote Originally Posted by afbug
    OT a bit. Sorry to hijack.

    BTW is there a way to protect wires? eg a earphone wire. Something like a cable sleeve? How do i go about doing it? Any idea?
    Not sure why you want to do this but you can buy cable sleeves in Sim Lim tower I think. If I remember you thread your wires through them (they look like black rubebr tubes and come in different diameters) and when heated (previously used soldering iron for this), they shrink and wrap their contents.

    The thing is you must be able to pass the wires through them in the first place. With the earphone buds on one side and jack on the other it may/may not be possible.

    Or use electrical tape lor :P

  14. #34
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    Default Re: How to make an external battery pack?

    Hi Eng Hong

    Just wondering the futurekit thing can provide variable V with 3A which is better than the one you show me that is only 5V with 1A?

    If I need 2.5A that means the board you have is not enough, right? It will not power up my device that need 2.5A, right?

  15. #35
    Senior Member afbug's Avatar
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    Default Re: How to make an external battery pack?

    Quote Originally Posted by Max 2.8
    Protect earphones wires? neccessary meh?
    Its actually for an antenna. The diameter is approx the size of a earphone wire.

    Quote Originally Posted by wantunn
    Not sure why you want to do this but you can buy cable sleeves in Sim Lim tower I think. If I remember you thread your wires through them (they look like black rubebr tubes and come in different diameters) and when heated (previously used soldering iron for this), they shrink and wrap their contents.

    The thing is you must be able to pass the wires through them in the first place. With the earphone buds on one side and jack on the other it may/may not be possible.

    Or use electrical tape lor :P
    Must i use a soldering iron? I never use one before. Hair dryer ok?

  16. #36
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    Default Re: How to make an external battery pack?

    Orh.......ok....

  17. #37

    Default Re: How to make an external battery pack?

    Quote Originally Posted by afbug
    Must i use a soldering iron? I never use one before. Hair dryer ok?
    Can....

  18. #38

    Default Re: How to make an external battery pack?

    Quote Originally Posted by Max 2.8
    Hi Eng Hong

    Just wondering the futurekit thing can provide variable V with 3A which is better than the one you show me that is only 5V with 1A?

    Erm did i show you one with 5V 1A?

    Quote Originally Posted by Max 2.8
    If I need 2.5A that means the board you have is not enough, right? It will not power up my device that need 2.5A, right?

    Not necessary, it may powerup but it may die real fast. These circuits are built with latency of sometimes up to 25% so depending on the components.

    Just read the 7805's datasheet. Its max output current only 0.5A so maybe you need to buy a readymade circuit, thses circuits make use of OP-Amps to amplify the current output. The circuit diagrams can actually be found online but its a headache to read.

    If you are still not sure, you can go to some of the shops at Sim Lim tower. Some of the shop owners do do circuits for people, just let them know whta you need and bring along what you have.

    Eng Hong

  19. #39
    Member eawtan's Avatar
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    Default Re: How to make an external battery pack?

    Quote Originally Posted by enghong17
    Erm did i show you one with 5V 1A?




    Not necessary, it may powerup but it may die real fast. These circuits are built with latency of sometimes up to 25% so depending on the components.

    Just read the 7805's datasheet. Its max output current only 0.5A so maybe you need to buy a readymade circuit, thses circuits make use of OP-Amps to amplify the current output. The circuit diagrams can actually be found online but its a headache to read.

    If you are still not sure, you can go to some of the shops at Sim Lim tower. Some of the shop owners do do circuits for people, just let them know whta you need and bring along what you have.

    Eng Hong
    7805 has many variants, the standard is 1A, 78M05 is 0.5A, there is also a 78H05 that can supply 5A and a 78T05 for 3A.

  20. #40

    Default Re: How to make an external battery pack?

    Quote Originally Posted by Max 2.8
    So I just get this thing from SIm Lim TOwer, solder them together and input with 8 pcs of 1.2V AA batteries(Sanyo) and the output will be 5V?

    Ok...if my X-drive last 2.5hrs with its built-in battery, how long will this thing of your works?
    1 thing the guys here forgot to tell you... this setup will be HOT
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