Hack 2 Devices for a Cheap Portable USB Charger and Ryobi Battery Charge Indicator




About: Mechanical Engineering student at the University of Texas-El Paso.

I would like to first apologies in advance if my instructions are not clear, as this is my first time posting an Intractable. After seeing a similar gadget that looked alike it required a lot more work without the added feature of having a battery indicator built in I decided to post mine. Please feel free to ask any questions especially if you have a hard time understanding my instructions.


Step 1: What You Will Need

Ryobi Model # P150 18-Volt One Plus Battery Fuel Gauge


GTMax Mini USB Car Charger Vehicle Power Adapter - Black for Apple iPhone 4 4G 16GB / 32GB 4th Generation


Soldiering supplies, A short peace of small wiring I used 20 gage wire.

Optional Supplies, Wire stripers, a wood burning kit with exactor blade tip for cutting the plastic case.

Step 2: Prepping the Battery Gage

(1.) Carefully remove the sticker so that you can reapply it at the end.

(2) Remove the 4 screws holding the unit together I used a 3.5 mm philips head screwdriver.

(3) After taking out the 4 screws the unit should come apart easily.

(4) You then can remove the circuit board and components buy lifting it straight out.

Step 3: Prepping the USB Charger

(1) Unscrew the 2 Philips screws on face of the unit one will be under the label.

(2) Remove the metal faceplate

(3) unscrew the end of the charger and remove the fuse and spring

(4) The circuit board should lift right out.

Step 4: Prepping the USB Charger Continued

(5) You should be able to lift the Metal flares on the Negative side right off.

(Optional) I removed the LED since I did not see a need to have it and I didn't want to have to redirect it or cut a small hole for it.

Step 5: Soldiering

Refer to Picture Notes

Step 6: Soldier the Power Leads

Above each post there are three points of contact with the circuit board that create a triangle it doesn't matter which of the three points you soldier your connection to so witch ever one looks easiest.

If you are looking at it with the center post closest to you then the left post is negative and right post is positive.

After making the connection I feed the wire down the already existing holes with the negative throw the top hole and the positive throw the bottom hole

Step 7: Marking Where to Cut

You won't to be as snug as possible without smashing the USB connection so that it will stay in place. I found that by plugging a USB cable into the plug you can prevent it from getting warped or bent since they tend to be fairly fragile.

You can always cut more away it's a little trickier to add it back

Step 8: Cutting the Case

I used a woodburning tool with an X-Acto blade to cut the plastic easily.

Depending on your usb car charger that you use you may need to cut the opening at an angle to accommodate for the short standoff distance from the circuit board to the lip of the USB plug I found that the plastic was thicker than the distance I had so I had to cut it at an angle to allow room for the circuit board to come closer to the opening allowing the USB metal flare to catch the plastic.

Step 9: Putting It All Together

It works grate and the battery gage works flawlessly!

It can be a little tricky to get the hole to tightly line up while not warping the plug I strongly suggest plugging a cable into it to ensure that nothing gets warped. It also gives you more control when positioning the plug since you having something to hold onto.

I am sorry I didn't take more pictures of me putting it together I got carried away with finishing and forgot I guess it's something you have to get use to when making instructions. If if will help anyone I can open if back up and take some pictures of it inside the case with one side off to give a better idea of how it fits in there



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    8 Discussions


    5 months ago on Introduction

    Thanks for the instructible. Mine works awesome. Really have to cut the plastic at an angle for the circuit board fit and for the USB flare to be flush to the plastic. Did an extra step by hot gluing in everything to lock everything in place. May also prevent the USB from backing in after so many uses. Extra precaution taken. Only drawback is, the battery tester does stay lit the whole time (so I know how much battery I got left) and need to get a 2A DC charger instead of my 1A. Thanks!


    3 years ago on Introduction

    This is Awesome! definitly better than those off the shelf portable USB power things.


    3 years ago on Introduction

    I made my with my flashlight. I added a RCA to my 10 watts LED flashlight. Made a CLA to RCA. I can charge different devices with different 12/24v chargers. I can also plug my laptop and many other uses. If I am out of power, I can plug it to my car.

    ryobi 1.jpgryobi 2.jpgRyobi 3.jpg

    4 years ago

    I just wanted to let you guys know that you should check your Home Depot to see if they still have their Ryobi 2 pack of 4ah batteries that where on sale for Christmas 99$ for the 2 pack because my Home Depot had their remaining packs on clearance 25$ for the 2 pack so less than 13$ a battery that's 87% off s


    4 years ago

    Looks good perrybear I'm sure your going to make good use of your batteries now!


    4 years ago on Introduction

    Great Instructable. I just finished the modification on my battery fuel gauge. I was able to squeeze in a USB charger with two ports, 2.1 ma and 1 ma. Everything works well thanks to your clear instructions.


    4 years ago

    This is an awesome idea. I'm surprised Ryobi doesn't make this itself.

    1 reply

    Reply 4 years ago on Introduction

    I was also surprised that they don't offer anything similar to this especially after seeing that DeWalt makes a usb charger for their batteries I just had to make something to utilize my 4ah batteries