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Thread: How to make an external battery pack?

  1. #1
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    Default How to make an external battery pack?

    Hi all who know curcuit board stuff!

    I used to use rechargeables AA batts for my hot shoe flash, eversince I bought some second hand Quantum batt packs, these rechargeable AAs were just sitting in my drawers.

    So I was thinking of using these AA batts as an external battery for my portable storage, mp3 player or maybe even media player.

    Just wondering if all you electronic engineering experts know how to make an small circuit board to regulate a 5V out of maybe 8 Sanyo 2500mAH batteries? Or even better a variety of voltage out of a few sets of batteries like the one East gear is selling?

    Just an idea...
    Max 2.8

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    Default Re: How to make an external battery pack?

    5/1.2 = 4 pcs... dunno if you can get that to work anot... anyway, some devices are voltage sensitive... might spoil if u over its allowed voltage...

    normally lower no problem, but some devices may treat it as low battery, cos normally when batteries are depleted, the current also drop...
    Logging Off. "You have 2,631 messages stored, of a total 400 allowed." don't PM me.

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    Default Re: How to make an external battery pack?

    Someone told me that too....to use 4 pcs=4.8V, should work lah...But I more ambitious lah, if can make a circuit board to regulate a constant voltage out of 8 or more 1.2V AA rechargeables, then this battery pack can last very long....right?

    If only I study electronic engineering....ai yah...regret bo tak chey already ah....

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    Default Re: How to make an external battery pack?

    Quote Originally Posted by Max 2.8
    Hi all who know curcuit board stuff!

    I used to use rechargeables AA batts for my hot shoe flash, eversince I bought some second hand Quantum batt packs, these rechargeable AAs were just sitting in my drawers.

    So I was thinking of using these AA batts as an external battery for my portable storage, mp3 player or maybe even media player.

    Just wondering if all you electronic engineering experts know how to make an small circuit board to regulate a 5V out of maybe 8 Sanyo 2500mAH batteries? Or even better a variety of voltage out of a few sets of batteries like the one East gear is selling?

    Just an idea...
    Max 2.8
    For 5V regulated output the typical will be a 7805 TO-220 (http://www.national.com/pf/LM/LM78M05.html). The problem with the 7805 is that the input voltage has to be >7.2V and is quite inefficient.
    One issue is the current drive, typical 7805 can only drive max of 1A, the 78M05 (in the link provided) is rated max 0.5A.

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    Default Re: How to make an external battery pack?

    Quote Originally Posted by eawtan
    For 5V regulated output the typical will be a 7805 TO-220 (http://www.national.com/pf/LM/LM78M05.html). The problem with the 7805 is that the input voltage has to be >7.2V and is quite inefficient.
    One issue is the current drive, typical 7805 can only drive max of 1A, the 78M05 (in the link provided) is rated max 0.5A.

    Oi Mr Tan,

    Lu Gong Si Mi? Dun understand leh....

    Anyway, if all these worked out, it will benefit alot of us here since most of us have Sanyo AA rechargeables. MAybe if we can meet up and make this thing out together...
    Last edited by TrailsofLife; 18th October 2005 at 04:08 PM.

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    Default Re: How to make an external battery pack?

    If u just want to power yr mp3 or portable photo storage, u can try this.
    Go to Sim Lim Tower (not Sim Lim Square) top floor, there are some electronics shops selling gadgets for students. Buy :
    1. plastic battery holder that can hold 4 AA battery (these normally white or black colour, come with electrical contact)
    2. some wires
    3. mini socket that fit yr mps or portable plug
    4. soldering iron and solder

    1pc of AA alkanie is 1.5V, 1pc of rechargeable is 1.2V, most electronic gadget eg mp3 can use 4xAA rechargable (4.8V).

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    Default Re: How to make an external battery pack?

    Can put more better, right? Astin.

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    Default Re: How to make an external battery pack?

    Quote Originally Posted by Max 2.8
    Oi Mr Tan,

    Lu Gong Si Mi? Dun understand leh....

    Anyway, if all these worked out, it will benefit alot of us here since most of us have Sanyo AA rechargeables. MAybe if we can meet up and make this thing out together...
    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 ?

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    Default Re: How to make an external battery pack?

    Quote Originally Posted by Max 2.8
    Can put more better, right? Astin.
    U dont need more, u need to know yr gadget what minimum voltage it requires. Look at the gadget spec, it is either on the bottom a sticker or in the manual, it will say operating voltage xx(V)-yy(V). Just add up the AA battery (1.2V each) to be more than the minimum then ok already.

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    Default Re: How to make an external battery pack?

    Orh...understand.....so there's no way to work around it? How did East Gear's ultimate battery pack work?

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    Default Re: How to make an external battery pack?

    The reason for 5V is because my iriver mp3 player, X-drive Super(can watch movie!), and Digimate plusII all have the 5V input socket.

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    Default Re: How to make an external battery pack?

    Also this A thing, how does it work? I have 4 sets of 2300Nimh batteries, how many A is that? X-drive Super have a label saying 5V 2500mAh is it the same A? iRiver & Digimate never label anything....

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    Default Re: How to make an external battery pack?

    Quote Originally Posted by Max 2.8
    Orh...understand.....so there's no way to work around it? How did East Gear's ultimate battery pack work?
    There are chips that have a "variable output voltage", that can be "tuned" by the user to get whatever voltage output is required.
    Another way is having various voltage regulators (eg 3V, 5V, 9V) avaliable on a large socket, then depending on the "cable" used, the "correct" voltage line will be connected.

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    Default Re: How to make an external battery pack?

    Wah...too Cheem liao....

    Mr Tan, you know how to make and where to get the little stuff? Teach me leh....

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    Default Re: How to make an external battery pack?

    Quote Originally Posted by Max 2.8
    Also this A thing, how does it work? I have 4 sets of 2300Nimh batteries, how many A is that? X-drive Super have a label saying 5V 2500mAh is it the same A? iRiver & Digimate never label anything....
    Most equipment don't label the required current (A thing), but may be indicated on the AC power supply, eg output 5V 2A.

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    Default Re: How to make an external battery pack?


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    Default Re: How to make an external battery pack?

    ok...just check my iriver is 5V 2A, X-drive super is 5V 2.5A and Digimate is 5V 0.8A.... Can they all use the same input?

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    Default Re: How to make an external battery pack?

    Quote Originally Posted by Max 2.8
    ok...just check my iriver is 5V 2A, X-drive super is 5V 2.5A and Digimate is 5V 0.8A.... Can they all use the same input?
    Yes, but your power source/converter must be able to supply 2.5A .

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    Default Re: How to make an external battery pack?


  20. #20
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    Default Re: How to make an external battery pack?

    Quote Originally Posted by eawtan
    Yes, but your power source/converter must be able to supply 2.5A .

    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.

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