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LIPO USB Charger – How to build

I have a lot of LIPO batteries in stock – most of them with the popular XT60 connector that I use on most of my drones.

The LIPO batteries are typicallly 2S, 3S or 4S – with a voltage level between 7-16 volt. But wouldn’t it be neat if you could charge your smartphone with the LIPOs on the airfield?
Of course the voltage of the large batteries had to be stepped down some how.

Sourcing the parts

My original plan was to build the circuit from scratch with some resistors and a 5 volt UBEC, like this project. There is quite a few projects on Instructables where a USB charge circuit is constructed.

But… while searching for a suitable UBEC on eBay with enough AMPS. I found something that completely changed and simplified the project – a Dual USB Output 6-24V To 5.2V 3A DC-DC Step Down Power Charger Module.

This little board takes a voltage input between 6 and 24V (LIPO > 2S to 6S) and outputs two standard USB 5V ports with a total output of 3A.

In order to make a working LIPO charger I just need two things – soldering a XT60 connector and some kind of enclosure for the charger.

3D printing the case for Portable LIPO USB charger

I considered designing a case on TinkerCad.com but then again why reinvent the wheel. Luckily someone already left a STL file on Thingiverse to print.

I printed the case with following settings in Cura 3D and with my Creality 3D CR-10:

  • Red PLA from Banggood.com
  • Layer height of 0.1 mm
  • 100% infill
  • Brim – could mostly likely also have printed with a simple skirt
  • Buildplate temperature = 70o
  • Initial layer printing temperature = 210o
  • Case for LIPO to double USB charger boardPrinting temperature = 200o

I accidentally selected Experimental Draft shield – which makes a thin wall surrounding the entire print. This was really not necessary and mostly for ABS prints. So I wasted a few grams and time printing the draft wall.

Download the STL file here.

 

Soldering and assembly

Welding the XT60 connector was pretty straight forward – usual Quadcopters require a least 16 AWG gauge wire. This project would not draw more than 3A so the wires should be more than 18-22 AWG.

I was thinking about adding a standard 12v DC socket also, since I would make the case more versatile. In the initial version I skipped this but might add it later.

The charger board has a little LED that lights up once it charges the smartphone. I drille a hole in the top plate above the LED and glued a piece of transparent plastic as a reflector of the light.

I glued the project together with standard high tension 2-component Epoxy glue.

The case was closed with 4mm M3 screws.

Testing the charger

I connected a 1200MAH 3S Turnigy battery and my Samsung S8.

It charged and was actually able to use the Fast Charge functionality of the Samsung. Project done.

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