The idea for this project started with my desire to not damage a new LiPo battery pack I bought for my RC dune buggy. I have a balancing LiPo charger, so the pack should be fine when charging, but when I'm driving, the only indication I have that a cell is dead is when the car doesn't want to go anymore. That's too late!
I know there are fancy RC systems that have telemetry features built-in, but I'm running low cost Chinese gear. :) So first the idea was to adapt some of my #LiFePO4wered/9.6V development to just shut the power off when a cell falls below a threshold. That's fine for an RC car, not so fine for a plane or drone. :) To make this more generally appealing it would be nice to get a warning before the power is cut off. So I decided the easiest way to do this would be to get an alert on the phone in my pocket. BLE is the most obvious choice to accomplish that.
Then I started to think that if I was already monitoring the cell voltages, why not send them to the phone for data logging? Of course, I couldn't stop there and decided current measurements would be useful as well. And what better way to make it all turn on and shut down automatically than by adding an accelerometer... which I want to monitor as well, of course. :)
There are a bunch of unknowns in this project. Will I be able to reliably turn on and off the large battery currents I expect? Will I be able to reliably measure these large currents? How well will BLE operate near the powerful motors and the 2.4GHz RC system? Only one way to find out! :)