Recently I've got my hands on a pair of cheap APM Power Modules from eBay with integrated 5V BEC and current meter (90A max). Although they are APM designed and will not work stright away with STM32 flight controllers like Naze/CC3D/SPRacingF3 (or rather would work only once since they are 5V scaled and those flight controllers require max 3.3V input) I have an intention to make them work!
So far, I've concluded that:
- current measurement is done with Texas Instruments INA169 and 0.5Ohm shunt resistor
- analog current out is 5V scaled, so probably 90A current flow results in 5V on meter output
- voltage sensor output has 1/2 voltage divider. We can ignore it, most SMT32 flight controllers have voltage dividers (CC3D does not, but 1/2 is not enough in this case)
- It more less works with a 1/2 voltage divider between current sensor and flight controller. Requires some tweaking, but something is measured. Will require scaling!
- Integrated BEC works, and this is all I can tell about it I'm affraid