Making a battery powered device run on 110v

Discussion in 'General Electronics Chat' started by Gdrumm, Feb 20, 2011.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    684
    36
    I have a few devices that I would like to run on household current, but they are battery powered devices.

    Example: I have a battery powered Air Compressor with weak batteries. They cost too much to replace for what the unit is worth.

    When I have it hooked up, and it is charging, it won't start up. It will only start after I charge it for awhile, and unplug the charger from the wall, etc.

    Is there a way I can wire this up to run off of the 110, when the charger is plugged in?

    Same question for Battery Powered drills, etc.

    Thanks,
    Gary
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    What size and kind are the batteries? Lots of power tools use NiCD batteries. Some might use sealed lead-acid batteries, some LiPo or other type.

    If the batteries are heavily discharged, the chargers' power will be going towards charging the batteries. Chargers are typically current limited, so there isn't power left to run the tool at the same time. Even after the batteries are charged, the charger probably won't add much "oomph" to the tool.

    The charger isn't designed to power the tool, it's designed to charge the batteries.

    Same answer for Battery Powered drills, etc.

    You would need to construct completely new power supplies designed to supply the current the tool requires to work efficiently, instead of charging batteries at a controlled rate.
     
  3. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    684
    36
    Would it be complicated to design such a power supply?
     
  4. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    684
    36
    Back on this topic, it's a slow day...
    I tore apart the old lead acid battery powered air compressor,pulled out the batteries, topped them off with distilled water, put it all back together and charged them overnight. So, it runs slow, but batteries aren't taking a charge very good.

    It's a 12 volt 24 amp device, and I'm using a universal charger, with multiple voltage outputs, set for 12 volts. I believe it is 422 ma.

    So, re-reading Sgt. Wookie's reply, might I be able to rig up a power supply that delivers 12 volts, with 24 amps?

    Better yet, I have a Waveteck Model 110 Function Generator that someone threw away, could I play with that and obtain a variety of outputs to run old battery powered power tools, or this compressor?

    Thanks,
    Gary
     
  5. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    You can get a 12V / 30Amp (13.8V, actually) SMPS power supply for around $100, one of those would replace the batteries, but then you are at a point where you could buy a more efficient 120V air compressor that plugs into the mains to start with.
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Show a picture of the batteries if you can...
     
  7. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,887
    1,016
    Or you can buy one of those battery operated compressors for around $30. You can get a nice plug in model from Harbor Freight or Sears for atround $60 assuming you are from the U.S.
     
  8. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    684
    36
    My camera has a dead battery (just kidding, it's at work).
    Anyway, they look like a batteries from an electric scooter.
    They are Chinese made Dayo 6FM7 batteries I believe.

    My moto is "spend no money"..., so I'm just tinkering with stuff.

    Could an old computer power supply be made into a device from which I could power up some old scrap battery powered drills, this compressor, and other such things?

    I read on a hack site, where a guy devised a way to run his digital camera off of a power supply, with the wires attatched to wooden dowels (the size of AA batteries) used in the battery compartment.

    I believe a lot of guys would consider buying such a device as I'm wanting to make, If it had set of adapters, and a selector switch..., they could power all the battery powered tools they have that don't work anymore, due to dead batteries. Replacement batteries cost almost as much as a new tool in most cases. I just hate to see good tools thrown away.

    Gary
     
  9. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,887
    1,016
    It seems awfully inconvenient to me. It is bad enough to have to worry about a power cord with power tools. Now you want to drag around a power supply?
     
  10. K7GUH

    Member

    Jan 28, 2011
    191
    23
    I recently purchased a recycled 12 volt 42 amp SMPS for $60. It works well, and was defiinitely worth the price. An old computer supply might work for your purpose, but you would have to know in advance if it's capable of 24 amps output. If the old ATX supply is hefty enough, try it and see, but be careful, you can fry things without much effort. A good check would be an automotive headlight. If the supply runs that without any blue smoke, it will probably run your power tool.
     
  11. AcousticBruce

    Active Member

    Nov 17, 2008
    58
    0

    He said spend no money and tinker. I'm not sure he cares about convenience.

    I cant see why a computer power supply would not work. And as far as I know computer power supplies are SMPS. These are EASY to get for free. My power supply does 45A on one 12v rail. Or so it says....


    Now I guess convenience would matter if your looking at inventing something useful for others to buy.
     
  12. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    The 45A@12V is correct if it is a newer power supply. Lots of boards are going to less current at 5V and 3.3V, and using 12V in for CPU, another two or four 12V inputs for video card, etc. Each part of the board then has a switching supply, so the CPU gets 1.2V@100Amps, Graphics gets 2.5V@90 Amps, etc. Similar concept of high voltage AC transmission lines, at 12V, normal gauge wires can carry the current needed if it is stepped down at point of use.

    My latest Power Supply is rated for 125 Amps on the 12V rail, but it's driving two higher end nVidia GPU cards (each takes two PCI-E 2x12V 6 pin power jacks). When playing a game, the computer is a nice space heater.
     
Loading...