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A project log for Simple Lithium-ion

complete all-in-one solution for using lithium-ion batteries on perfboard

Matthew James BellafaireMatthew James Bellafaire 12/21/2019 at 14:530 Comments

I've been on break for a good bit of time and as a result i've been putting some serious time into my projects. I've spent some time putting this project off since for the rev 3 I wanted to go with components I could source from digikey (which are significantly more expensive than LCSC). Either way this version of the project diverges pretty significantly from the previous 2 iterations.

The primary change made to this project is the use of an ATTiny25 on-board, this micro-controller comes in at about $0.43 which is pretty crazy considering the window comparator I was previously using (the MAX9065) costs close almost twice that. The ATTiny25 replaces the MAX9065, to handle battery voltage measurements the project will use an adapted version of my battery management library (https://github.com/Bellafaire/AVR-Battery-Monitor). The result of this is that the new board can handle over-voltage, under-voltage, and overcurrent protection. There is also an on-boar tactile switch which will be used to reset in an over-current condition or just to turn the board off. Here is the full schematic:

Overall I look forward to the flexibility that using a micro-controller for this project will lend me. Programming each and every board would normally not be ideal for production, but since I primarily intend to use these board (and this schematic) for my own personal projects it seems to fit my needs pretty well.

Other noteable new features added, the inductor has been upgraded, and the layout has been re-thought, the board can now handle up to 3A coming from the battery (meaning roughtly 2A on the output). There are also two indication LED's on board, one connected to the charge controller (MCP73832) and one connected to the micro, these will give some indiciation about what the board is doing at any given time (indicating fault, on/off, etc.).

Either way that's everything, see you in the next log!

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