I’ve been thinking about creating my own LiPo charger for a while now. Something that will allow me to charge a large array of LiPos in the field without it been fiddly or annoying.
Since I now know a bit about electronics, I set out to see what it would take to make a simple and modular single-cell LiPo charger. Something based around the MAX1555 or the MCP73831. I chose the Microchip one because I liked the fact that the datasheet had a recommended layout for the PCB tracks to improve the thermal properties.
For the daisy-chaining, I’m using these cool hermaphroditic connectors from TE. They handle up to 6A, so it should be good for a few chargers in one chain. And they’re only 79c!
For regulation, I’m using a Murata switching regulator to get from Xvolts (where X can be a car battery) to the 5V the lipo charger chip likes (thanks Kean for the suggestion!). They’re not terribly cheap, but they’re efficient and kinda small.
I’ve also put on one end a USB socket to allow charging of a single battery off USB. There a lot to be improved in that corner, and I don’t think it’ll be the primary usage, but in a pinch it could be very handy. Since USB only allows 100mA draw without negotiation, I’ve laid out an ATTINY there to act as a USB device that wants more power. There’s a lots of suggestions flying around, like, put a fuse there (Madox, Jaye), and they’re all good ideas, but I haven’t gotten around to implementing that yet.
All of this experimental, of course, but this is the fun part!
Download the EagleCAD files here: MCP7383_v1