|DIY lipo charger|
Of course the idea is not mine and the only thing I did is to layout the components in a way that is easier to solder them together without an actual PCB. The instructions and component list you can find in this web site and all credit goes to the author. This is the version 3 schematic with LED and variable charging current.
At first I had no idea how big this will be and ended up wasting some space on the perfboard but this is ok as I do need space for the heatsink. One thing that I did is to separate the charging current selector from the main board with the help of some header pins. This allows me to either insert just the right resistor in the female pins and make this more compact or use the add-on board for different batteries.
|Close up of the lipo charger|
|The 2 boards of the lipo charger separated|
As you can see the circuit is simple and every component is cheap. The most difficult part was sourcing the right trim potentiometer as I ended up buying 3 or 4 until I found the right one. I ended up doing 2 additional trips to the parts store because in the bin where all the 500 ohm pots were most of them where actually 50 ohm. When I went there the third time I grabbed my multimeter to make sure I will get the right one. Now that I have leftover parts (is there a case when you won't have leftovers?) I need to find another project to use them.
|"main" board of the lipo charger|
|back of the "main" board of hte lipo charger|
Don't mind the crooked heatsink it has a notch that prevents it from sitting flush with the LM317. I will replace it soon because I feel it is too small, the LM317 really gets a bit hot to the touch when charging a small 3.7V 200mA lipo battery. It works but to be on the safe side it needs to be bigger (this is 'merica bigger is better). If I use 9V as input then it does not get hot at all, that is a solution as well, just use a closer to the output current.
I am quite happy how this turned out as there are very few overlaps and this could actually be used for a PCB schematic.
|current selection board of lipo charger|
|back side of current selection board of lipo charger|
This is about it for this project, I found it very useful and hope it helps.
Good day to you sir!