Making things

jwatte's picture
I make things. At work, I make software -- and, being super busy, I don't have much time to blog about all the cool stuff we do to grow IMVU.
During my "copious" spare time, I do things that aren't software. Like hardware. Of course, hardware still needs software, but if I get frustrated with a mis-behaving microcontroller serial bus interrupt, I can always just wield a soldering iron and put something else together. Today, I put together a 12.8V 10 Ah battery pack with built-in charging controller and protection circuitry using less than $150 in parts! It was actually quite easy:
From parts:
picture of parts
To finished pack:
picture of assembled lifepo4 battery pack with protection circuit board
The circuit board is a charger controller and protection circuit. It makes sure the cells are charged to the same voltage once they start reaching the top. It also makes sure they are not over-charged, nor under-charged, and also has over-current and over-temperature cut-offs. Nominal voltage is 12.8V, fully charged is 15.8V and fully discharged is 8.8V.
The black and yellow wires are ATX CPU style power connectors, because they in turn are intended to power a picoPSU that plugs into a mini-ITX motherboard with a 30 GB SSD, a Core i5 2400, and 8 GB of RAM, running Linux. In fact, I'm sharing this photo from that very machine!
However, the picoPSU doesn't do enough switching control to deal with almost 16V of input power -- it cuts off at 14V, which was a bummer when I found that out. Instead, I apparently need an "M3-ATX" which is the "car power" version of the picoPSU (and twice the price.) That can allegedly go from 6V to 30V input, which is much wider than I need :-) Being a Maker, for a while I investigated building my own buck/boost switching controller to take anything 8-16V to an even 12V, but I decided to punt on that and pay for the M3-ATX from Amazon. I have a robot to make!