Power adapter for cordless tool

Discussion in 'The Projects Forum' started by Ripperoo, May 23, 2014.

  1. Ripperoo

    Thread Starter New Member

    May 23, 2014
    Hi Guys

    I'm new here and this is my first post, so not sure if this is the correct place to put this, but here goes.

    I have a lot of 18v power tools (approx 20) from the same manufacturer which all take the same 18v NiCd battery (NiMh and Li-Ion versions also available).

    However, I would like to be able to run these power tools via either:

    • Modified Battery, Containing 240v/18v Transformer.
    • Mains powered 18v transformer
    I know this kinda defeats the object of the tool being 'cordless', but there is reasons for wanting to do this.

    Although you cannot beat the portability of cordless power tools, there has been occasions when I have needed to use several tools at once in close proximity to mains power.

    During these times I would've preferred to use 'corded tools' to eliminate 'battery change/charging', but cannot justify having both corded and cordless of the same type of tool.

    The best of both worlds would be a kind of 'Hybrid', if that's the correct terminology, which can be used cordless when needed, but which can also be used via the mains supply when mains is available near the work area.

    When I originally thought about this a few years back, I naively thought it was an original idea, but I have since found out that many others have appoached this subject with varying degrees of success.

    I also discovered that DeWalt had done something similar for their 24v drills, but it never caught on.

    Some folk have even created their own 'transformer/adapter/device' from various parts, so it can be done.

    There's two ways I see to acheive this and these are as follows:

    • Transplant a 240v mains powered transformer into an empty battery, which outputs 18v to power the drill, jigsaw etc.

    • Have a 240v mains powered transformer, sited close to power outlet, with 18v power via cable to an empty 'modified' battery (for the electrical connection).
    Very simple, idea, but with many major benefits from what I can see:

    • Abilty to use mains power when in the proximity of mains socket.
    • Longer useage times for those with limited number of batteries.
    • Extended battery lifespan due to batteries only being charged when 'Going Remote'.
    • Less Battery Changes' if working near mains power.
    • Less batteries required by user, so keeping the end user cost low.
    • Less batteries produced by manufacturer, which would be better for the environment..
    • More envirnmentally friendly (less dead batteries going to landfill).

    There's probably many other good plus points, but these are the ones I could think of right now.

    What I would like to know is whether this is a viable project.

    Transformer In The Battery Compartment:
    Is such a transformer available that will fit into an empty battery?
    Will the transformer be susceptible to overheating using this method?

    I prefer the other method as it would mean for a lighter tool due to the transformer being 'remote'.

    Going by the findings of other people who have done similar, it would appear that the 18v tools (reciprocatiing saw, circular saw, jigsaw, hammer drill) require in the region of 8-10 amps when under load.

    Maybe someone more qualified could advise otherwise as I've also seen 30 amps mentioned.

    Another solution may be to use an industrial 240v/24v transformer (purple power plugs), such as the one below:

    VA: 400
    Input vac: 230v
    Input Current: 1.74a
    Output vac: 24v
    Output Current: 16a

    Would 24v be too much?

    Then it would be just a case of making up a cable with 24v plug on one end an a 'modified' battery pack on the other.

    Cheers guys.
    Last edited: May 23, 2014
  2. wayneh


    Sep 9, 2010
    Hmmm... A laptop power supply brick puts out ~19V and I was thinking one might be an easy-to-find and inexpensive solution for you. But 10A would be 200W and that's larger than most (I've not seen one >150W). 30A is a different beast altogether.

    But anyway you are looking for a switch mode power supply (SMPS) with the right voltage and a current rating that covers any usage you might have. The laptop ones already have over-current and thermal protection built in, and I think you would want those features.
  3. MrChips


    Oct 2, 2009
    24V might be too much for a 18V tool.
    I would aim for 18-20VDC output.
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
    take an old dead battery back and take out the insides. connect wires to the connetions and use it to power your drills and stuff.
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
  6. inwo

    Well-Known Member

    Nov 7, 2013
    I don't believe a transformer will work. You will need a DC supply to make the PWM speed control work.

    A ten amp 12volt transformer into an unregulated supply should be be a good place to start.

    Drill should be fine with a large voltage dip under load.

    Moderate load is about 10 amps on 18volt dewalt. 50 amps locked rotor on battery pack.

    The 10 amp transformer will handle intermittent high current.

    I'd be tempted to try 18v unfiltered dc for better regulation. I'm not sure I want to risk one of my dewalt trigger switches though.:D

    I'll try a search for a switch schematic.
  7. inwo

    Well-Known Member

    Nov 7, 2013
  8. crutschow


    Mar 14, 2008
    This might be of interest.
  9. MaxHeadRoom


    Jul 18, 2013
    I think someone beat you to it!

    I am pretty sure I can get a large enough Toriodal TFMR into my battery case, add a bridge an a electrolytic and I will post result if it works out.
  10. Ripperoo

    Thread Starter New Member

    May 23, 2014
    Thanks for the answer Wayneh

    During my searches around the internet, laptop power supplies have been used, but the output power is not that great. Especially with the more demanding tools.

    There is a guy who constructed one using a 'Meanwell 350w DC PSU' (15-18 volts) which can be seen on the INSTUCTABLES website.

    I may have a go at this if I cannot find a 'Ready Made' solution.
  11. Ripperoo

    Thread Starter New Member

    May 23, 2014
  12. wayneh


    Sep 9, 2010
    There may be more options if you look for high current capacity at a 12V nominal voltage. That linked story noted that 18V battery voltage sags quite a lot under load, so a 12V supply that doesn't sag would be not all that different. To verify this you could try your tools with a 12V car battery and see how they perform.

    I could be wrong, but I suspect there are more options at 12V.
  13. Ripperoo

    Thread Starter New Member

    May 23, 2014
    Any sugggestions?

    I did watch a video where a guy had built a 12v car battery box and managed to get most of his stuff working to some degree, except for the heavy load stuff such as 18v mitre saw and the like.

    He was using a 12v > 18v car laptop adapter though to get the full 18v:
    18v Power Tools From Car Battery
  14. Ripperoo

    Thread Starter New Member

    May 23, 2014
    What about this?

    The eFuel 30A Power Supply (£80.00)
    Your eFUEL switching DC Power Supply is designed to use household AC power source to power equipments that required DC power. The eFUEL converts standard household power 100-240V AC to 12-18V DC power and can supply up to 30 amperes of continuous power.


    • Two DC power outputs, up to 30a
    • Output voltage adjustable 12-18V
    • Large LCD indicates voltage and current amperes output
    • Two USB ports, 5 volts, 1000mA
    • Smart cooling fan
    • Over temperature protection
    • Overload protection
    • Short circuit protection

    Or, better still this:

    eFuel 1200W (15-30v) 50a Power Supply



    • 1 x DC power output, up to 50a
    • 3 x 10a Outputs (On/Off)
      Output voltage adjustable 15-30V
    • Large LCD Display
    • Two USB ports, 5 volts, 2100mA
    • Smart cooling fan
    • Over current protection
    • over voltage protection
    • overload protection
    • Over temperature protection.
      Short-circuit protection (on output)

    There is also a 'eFuel 1200W (15-24v) 60a Power Supply', but I can't find the specs on the website.
  15. Johann

    AAC Fanatic!

    Nov 27, 2006
    Looks good! I suggest you use 2 x "ANDERSON" DC plugs instead of the one illustrated in the video. Available from dealers in camping equipment or electrical wholesalers. Good connection and will allow you to at least use wire that is capable of carrying the required amps. The guy in the video did not show what happens when you do some real work with your cordless tools using that thin wire and small DC plug on the end!
  16. Ripperoo

    Thread Starter New Member

    May 23, 2014
    If you mean the ones below, then I did actually consider those.

    But I think I will end up using industrial 24v 16a connectors (violet) that we have in the UK (not sure about elsewhere) as shown below:

    I would probably opt for the 3 pin version though, but couldn't find a decent photo.

    I'll also be using much thicker cable between the power supply to the 'converted battery @ 3x1.0mm² x 3metres long (similar to the cable on your averge IEC TV power cable)

    That way, if anyone was to 'accidentally' plug in a device with a compatible connector, the voltage would be less than the equipment plugged in.

    I hope that makes sense! LOL
    Last edited: May 25, 2014