I'm building a music box based on a Raspberry Pi and a HifiBerry AMP2 amp. The amp unit takes 12-24V DC and supplies the Pi with 5V. I want to be able to power the amp/Pi by either a mains adapter (16V DC switching mains adapter), or LiFePO4 batteries built into the music box. I bought this cheap battery management module to experiment with:
The module has these connections: a 5-pin plug for monitoring/protection of the cells, a solder patch labelled C- (charging negative terminal?), a solder patch labelled P- (power out negative terminal?), and a solder patch labelled B- (battery negative terminal?).
The only usage documentation is a diagram on the unit indicating that B- should connect to the negative terminal of the first battery in the series and that P+ and C+ should connect to the positive terminal of the last battery.
So, first, am I right in thinking that this unit would normally charge from C- and C+ and that I should take power from P- and P+?
Second, will my proposed circuit below work as a power supply for my amp/pi, so that when the mains adapter is plugged in power will come from the adapter while allowing the batteries to charge, and when it's not charging the power will come from the batteries?
The terminal blocks in my diagram represent the connectors on the module, the two diodes are 10SQ050 10A 50V Schottky with a specified voltage drop of around 0.5V and J1 is the power connector from the 16v supply.
The reason I'm using the two diodes and supplying power from C- and C+ is so that current won't be flowing through the BMS while the box is connected to the mains. Considering that the BMS will hold the batteries at a constant 3.7V once charged I'm hoping I can just leave the thing plugged in to mains without harm. Is that right?