Finishing off small batteries

JetMech
JetMech Solar Expert Posts: 71 ✭✭✭✭
in Energy Use & Conservation #1
I suppose this is Energy Use...perhaps Conservation...but I wasn't sure where to put this since it is sorta off topic...

We have several gadgets in our house that are battery powered, most of which I use NiMH rechargables, but some things just seem to work a lot better or longer with regular alkaline batteries. However, some of those batteries need to get replaced before they are completely "dead". I am trying to think of a productive way to polish off the last bit of juice before throwing them out. I was thinking about a small fan, like a computer fan, and maybe help move some of the hot air out from behind the fridge. I know it wouldn't be a big help, but it least tomething useful could be accomplished. Only problem is I can only find 12vdc fans which would mean I would need 8 AAAs at a time. I would prefer to do 2 at a time on a 3vdc fan but I can't seem to find any of those. Any other practical ideas?
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #2
    Re: Finishing off small batteries

    Get a cheap digital camera. That will kill off some juice in a hurry.
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  • Slappy
    Slappy Solar Expert Posts: 251 ✭✭✭✭✭✭
    #3
    Re: Finishing off small batteries

    the 12v computer fans "muffin fan" will run on alot lower voltage, but it will turn slowely, but as for any other ideas? try a L.E.D. for a bathroom night light?
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  • JetMech
    JetMech Solar Expert Posts: 71 ✭✭✭✭
    #4
    Re: Finishing off small batteries

    Some of these are from digital cameras that still have power in them but not enough to keep it powered up.

    The LED is a good idea. I'll also give one of my spare muffin fans a try and see how they do. I didn't know they could run on lower voltage.

    Thanks.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #5
    Re: Finishing off small batteries

    12V brushless muffin fans need about 6V to start up.

    2 batteries in series, with a limit resistor, will run a LED for a night light several days.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #6
    Re: Finishing off small batteries

    You might want to give this a shot:

    http://en.wikipedia.org/wiki/Recharging_alkaline_batteries


    Afroman has been there and done that:

    http://www.afrotechmods.com/reallycheap/batteries/batts.htm
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #7
    Re: Finishing off small batteries

    be careful as sometimes they can rupture hard and fast enough to be classified as an explosion and in trying this, be sure it is not going to do harm to people or property should it explode. even smaller charge rates may prevent this and i don't believe it will take very much of a charge compared to its original capacity. even if you successfully get a small charge into an alkaline, do not think this can be done for thousands or even hundreds of cycles as this is not the case. if you do this 10 times consider it a success.
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  • Slappy
    Slappy Solar Expert Posts: 251 ✭✭✭✭✭✭
    #8
    Re: Finishing off small batteries

    I didn't know they could run on lower voltage. Dc motors can run on lower voltage, Example, my computer fans are hook to the 5v line of the power supply so they are quiet but still move the hot air out of the case. I have 2 12v radiator fans hooked in series so it sees it as 6v, runs at half the speed and quiet, it cools the house(window mounted). Also got a 144v dc motor that runs strong on 12v. (for my EV), wew thats going to be on long project. Yes but DC motors can run fine on less voltage but does not like higher voltage. But what is cool though is a 12v radiator fan hooked to 36v and watch it fly like a space ship!
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  • blackswan555
    blackswan555 Solar Expert Posts: 246 ✭✭
    #9
    Re: Finishing off small batteries
    We have several gadgets in our house that are battery powered, most of which I use NiMH rechargables, but some things just seem to work a lot better or longer with regular alkaline batteries
    .

    Most rechargeable`s are 1.2v not 1.5v like a standard AA etc, Thats why they are poor in high power/voltage sensitive applications EG Digi cameras

    Have a good one
    Tim
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #10
    Re: Finishing off small batteries

    the problem isn't the rechargeable batteries, but the fact they designed the cameras for the higher voltage of the throw-away primary batteries. fully recharged nicds or nimhs appear to be like drained alkaline batteries to the cameras with upwards of around a .6v difference between the 2 types when 2 batteries are in series.
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  • JetMech
    JetMech Solar Expert Posts: 71 ✭✭✭✭
    #11
    Re: Finishing off small batteries

    Yep, that is where my batteries seem to run out the fastest...makes sense now. The LED is a good idea, that should use every last bit of the battery. Maybe I can find a schematic to allow a single led to come on only when it is dark.
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  • blackswan555
    blackswan555 Solar Expert Posts: 246 ✭✭
    #12
    Re: Finishing off small batteries
    blackswan555 wrote: »
    .
    Most rechargeable`s are 1.2v not 1.5v like a standard AA etc, Thats why they are poor in high power/voltage sensitive applications EG Digi cameras
    Tim

    To add , I always wondered why they are 1.2 v , I put it down to if they made reasonable re-chargeable`s, The market for "normal" 1.5v`s would dry up ? Any one know the correct reason, I can not see it is a size problem ?

    Have a good one
    Tim
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  • _OS_
    _OS_ Solar Expert Posts: 207 ✭✭✭
    #13
    Re: Finishing off small batteries

    I have a lot of small digital temperature sensors with display around the house that I use for this purpose. When an AAA battery in a remote control or something is "dead" I keep it for later and use it in one of the temperature sensors where they last many months and sometimes years.

    Ole
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  • _OS_
    _OS_ Solar Expert Posts: 207 ✭✭✭
    #14
    Re: Finishing off small batteries
    blackswan555 wrote: »
    To add , I always wondered why they are 1.2 v , I put it down to if they made reasonable re-chargeable`s, The market for "normal" 1.5v`s would dry up ? Any one know the correct reason, I can not see it is a size problem ?

    Have a good one
    Tim

    The reason the voltage is 1.2V (NiMH), 1.25V (NiCad) and 1.5V (alkaline) is cell chemistry and cannot be changed.

    Ole
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #15
    Re: Finishing off small batteries

    And Hg "buttons" are something like 1.35V and LA about 2.12V.
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