USB Charger From Makita Batteries




Having the power go out a few times this year for over a day or more at a time left me without a way to charge portable electronics, iphone etc. Besides running out to the truck (to use the 12v port) in the middle of a storm I wanted to see if I could use the batteries from my power tools to charge them. Having 12v adapters for use in vehicle's I came up with a way to connect a cigarette lighter socket to my Makita batteries.

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Step 1: Holder for Cigarette Lighter Type Power Socket

I was initially going to fabricate the holder for the 12v port, then I remembered I had a burnt out impact driver I was saving for parts. I lucked out and the 12v port fit in side the handle. Unfortunately the power socket that I have will ended up sitting well above the top of where I plan on cutting the housing but that won't be a problem.

Step 2: Cutting the Housing

I was pondering wether to wire a step down circuit from 18v to 12v but seeing that the adapters will take 12 - 24 volts I decided just to add a fused link.
I Started by cutting the top of the housing off just above where the trigger was.

Step 3: Fusable Link

I used 2 Blue Female blade connectors with the plastic removed  and automotive blade fuse (10a) for the fused link

Step 4: Wiring the Power Socket

I started by soldering 2  wires, longer than I needed  to the + and  - of the cigarette lighter type power socket and checked conductivity . I used 12g automotive wire ..... well because that's what I had.
Then found place on the Housing where I could put the fuse and cut a slot.

Step 5: Making Fuse Holder

To make the fuse holder I needed  to secure the female blade connectors to the Housing. I had some Modeling Plastic, that melts in hot water and hardens at room temperature which made for a fast setting application. Other material like epoxy, bondo, Surgu could be used.
I greased the blades of the fuse and put the female blade connector on the fuse, placed the fuse in the slot I cut out in the housing and applied the plastic to the inside. Once the plastic harden I removed the fuse and now have  an inline fuse holder. After I did this I realized I should have soldered the wires to female blade connectors first................ oh well I made work.

Step 6: Finish the Wiring

Now I laid out the power socket  to get the wire length to connect to the fuse holder and the Battery Terminal, cut the wires to size the neg. inline to the fuse then soldering yellow female blade connectors (plastic removed) to the ends to connect to the Battery Terminal. Check Conductivity 

Step 7: Filling in the Top Gap

The power socket that I had ended up sitting well above the top of the housing so I used Water Putty to fill in the top and to secure the power socket to the housing. First I sprayed white lithium grease on the empty side of the housing as a mould release, stuffed plastic wrap under the power socket to stop the Water Putty from filling the inside up. Assembled the housing together and used masking tape to make a mould around the top, mixed the Water Putty and poured in the top and let sit fer a day to set.

Step 8: Shape Top and Finish

Removed tape then gently separated the housing and removed the stuffed plastic wrap. Rechecked the wiring and reassembled housing so I could shape and sand top. Masked the housing and the top of the power socket and used some rubberized truck Bed spray I had to cover the Water Putty area, let dry.

Step 9:

Slid a battery on checked the power and inserted the USB adapter. Now I have a portable power socket to use with the batteries that already have.

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    10 Discussions


    6 years ago on Introduction

    Brilliant ! I was actually just about considering buying the milwaukee 12v "box" only because it comes with a 12v cigarette socket. Thank god that I stumpled upon your article today. I will emediately start copying your (much much better) idea :)

    Casper Christensen, Denmark


    7 years ago on Introduction

    Thank You! I hope to have one of these soon for myself. :P


    7 years ago on Introduction

    what's that "truck bed spray" you used?

    i've been looking for a decent spray-on stuff like that and there are many products, with varying reviews.

    i just need a tough, textured finish for my projects. any recommendations ?

    2 replies

    Reply 7 years ago on Introduction

    Iv'ed used duplicolor, EZ Liner and RUST-OLEUM Truck Bed Coatings. All seem to hold up good as long as you prep your surface right. Prime bare metal, scuff up painted surfaces remove greese and dust etc.
    RUST-OLEUM has a nice any angle spay tip which is good fer those awkward jobs.


    Reply 7 years ago on Introduction

    thanks for the swift and helpful reply, will really help me out with putting a great finish on some of my projects :)