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12v Battery pack using AA

Discussion in 'Night Vision Optics and Illumination' started by d900man, Mar 24, 2014.

  1. d900man

    d900man Engaging Member

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    After blowing my 12v battery last night I have decided to build my own using AA batteries.

    I know I need 8 x 1.5 AA batteries to give me 12v but my problem lies with how long it will last.

    The batteries I plan to use are 2200mah and will be powering a bullet camera and also a 4.3" screen.

    Would I be asking so much to get about 3 hours out of it?

    Any help muchly appreciated.
     
  2. SteveO

    SteveO Top Poster

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    How did you blow the battery Ben? :confused: Overcharge?
     
  3. NickHammond121

    NickHammond121 Engaging Member

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    and don't forget that rechargable AAs are only 1.2v not 1.5v so you'd need 10 for the 12v total
     
    Last edited: Mar 25, 2014
  4. d900man

    d900man Engaging Member

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    Yeah. Plugged the wrong charger in lol
     
  5. genisis22

    genisis22 Engaging Member

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    hi, as a thought for you, I use 3x14500 bats that are the same size as AA, but are 3.7 v 2200mah rechargeable protected cells, they are in a AA battery box with lid and switch on underside of unit, they are backed up by a 3/32 volt dc/dc voltage booster set to 12.5 volts [bats give 12.1 full charge] as the volts in bats drop the booster takes up the slack back up to 12.5v [ cam and screen units normally 12 v +- 10% so well within limit] this allows the bats to give power right down to the protected shut down without over discharge, for me works very well and is tiny and light weight
    couple of pics to show set up, a sparer set of three are carried just in case but havent had thee need to change them,
    [​IMG]
    [​IMG][​IMG]
     
  6. snapperspike

    snapperspike Engaging Member

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    Be interested in the details of the dc-dc booster please.
     
  7. d900man

    d900man Engaging Member

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    Any details of the voltage booster you could supply would be great.
     
    Last edited by a moderator: Mar 25, 2014
  8. genisis22

    genisis22 Engaging Member

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    hi chaps this is the one I use, which is variable output via little brass screw on top of blue box Needs soldering power in + - Then read output with multi metre untill desired v out is achieved, then solder in as usual
    http://www.ebay.co.uk/itm/LM2577-DC..._Measurement_Equipment_ET&hash=item1e7bd17faf, it is a very fine multi turn pot so it takes quite a lot of screwing, the theory behind this is that with a contant 12.5 volt the current draw is less, without reg ,as the voltage drops ,this is compensated for by more current,ie amps so batterys flatten in a ever increasing rate, it has been said on forum that set up,s will run on lower than 12v maybe as low as 8/10v, there is no free lunch the lower the volts below optimum the more current is used to replace it,
    PS, no heat sink was used as the volt changes are not huge
     
    Last edited: Mar 25, 2014
  9. audiguypaul

    audiguypaul Donator

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    Ive just made a pack from 3 x Panasonic 18650's 3400mah and a series holder from ebay, total about £30. Left it switched on and ran my camera and screen for over 12 hours. Ebay numbers 181311071822 and 281199951833.

    atb Paul

    View attachment 92994
     
    Last edited: Mar 25, 2014
  10. terry1001

    terry1001 Major Poster

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    The 18650 cells are about double the capacity of the 14500 type, if you want to double it again the 26650 cells run at over 5000mah but they are starting to get a bit chunky! With these you only need 3 cells to get a nominal 12 volts but with AA you will need 10 which will take longer to charge unless you've got several chargers for them.
    Suitable RC model battery packs can be bought quite cheaply but do need a dedicated balance charger but even these aren't too expensive, the Hobby King UK warehouse has a good choice. These packs have different connectors (which fit the chargers) and for the output you would need to make up an adapter to connect to the cctv type power leads.
     
  11. Alex.mc

    Alex.mc Busy Member

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  12. merjp

    merjp Active Member

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    Just a couple of notes. Any of the above model battery packs will do the job. The ones highlighted are 11.1v which indicates that they are basically three 18650's in series. There should be no problem in using three good quality 18650's in series of equal capacity. In series the voltage out will only be maintained at nominal 11.1 until the lowest capacity battery exhausts and then your voltage will drop to less than 7v even though the other two may still have some charge remaining. That is why i highlight getting batteries of good quality and equal capacity. That has or should have been done with the model battery packs.
    I wouldn't recommend using 10 Nickle Metal Hydride batteries it is a lot more bulky, weighty and may drop to lower nominal output voltage than LiIon pack as it discharges.
    Using the DC to DC converter will deliver a constant 12v regulated but the price you pay is efficiency. The regulator is about 80% efficient so around 20% of battery energy is lost as heat in the regulator. If you have over capacity then it is a good solution.
    The only additional comment is that some of the model battery packs and good quality 18650's will have over voltage and discharge protection. Worth paying for as some of the cheap Chinese rubbish does not.
     
  13. stoogey

    stoogey Engaging Member

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    added as side info... nicads need to be balenced too. three 18650's seem to be about the narm today, theres various cages about fort them, try a search on ebay for pcp protected battery cage 18650.. im the real world, 2700 or there abouts is actualy acheivable in the buying department for nicads, in the 18650 type lithiums about 3300 is all you get top end, no matter how big and fancey surefire write 6 amp or 15amp..SURE FIRES ARE 1 AMP REFURBS.... if you actualy wat 4 amp cells, try soshine 4200mah 26650 cells..tried and tested. adding in series adds the volts, adding in parallel adds the capacities, but......after two cells in parallel you get less for three less for four etc, as in 2 amp cell plus 2 amp cell..pritty much a 4 amp pack. add three you get 5 amp not 6, varies from cell type to cell manufacturer. cells thyat are unbalenced can run for some time, and dont always exspode sooner or later..not always lol, most stop workingthough prematuraly because one cell is so far out it gets buggered up by the the other cells.(then after a bit it go bang..not always though.)

    edit...capacity wise as a guestimate fore use, 1 amp capacity 800 mah use will get 1 hour, sort of less thaan a third more than a 1/4 less than stated on the label (or real figure on the hobby charger).

    e.g. 3300 batteries often come in at 3000mah for 1 brand consistantly, or 2700mah nicads come in at 2400's as do the 2400's the 2500's the 2000mah 'pers lol, i.e. theyre all thame for some brands.. its pain sussing whoswe is what.

    a note to making the packs DONT heat the cells up pre soldering...fffff nicads have vent holes, when they get hot they vent audabley, alas each venting although stopping it exspoiding in the case does shorten its life span, say 800 rechargeres fot 1/25'th C charge cycles 400 recharges for fast charge 5 amp.

    back to the soldering, run the solder off a 70 watt or more ire iron, pretin the wires and use flux, fasten the pack in shape before you start and wire is just as good (6 amp stuff helps hold its pack shape).

    reflo solders? dunno tbh, i bet theres some for it some where, but the second a nicad pack kicks out power they get hot (as in cant hold them hot, within their perameters though) i cant help thinking the reflo stuff may well just drip off..

    not soldered any lithiums...theyre twitchy enough as it is lol, the bang is equivilent to about 3 shot gun catridges going off with no barrel arrond them, nicads, touch wood i havent had any go bang yet.

    rechargge nicads from flat, the memery affect will and does kill a pack much sooner than later, metal hydrides have a few advantages but dont like too hi a release, and as hardy as advertised they dunarf suffer being to flat, e.g. 3 times over flat they die verses years later the nicad finaly dies after all that abuse lol.
     
    Last edited: Apr 4, 2014

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