I previously asked asked an advice on power control of battery operated system.
The problem was to cutoff the battery when low to avoid overdisharge.
I have built the device according to Olin Lathrop's advice to add hysteresis to avoid oscillations. Unfortunately this does not work. The oscillations still appear in very unpredictable way.
Is there a way to add a control with stable hysteresis and preferably with reset button.
My current schematic is: stable voltage is compared with battery voltage at the comparator, when certain threshold is achieved the comparator switches and switches off the load via power mosfet, 200mV positive feedback from is added to input of comaparor to add hysteresys. It work perfectly fine in simulation software but still oscilates in real life.
The problem might be in capacitance of the load or whatever. I need a different approach, something that would latch and hold the OFF state.
Best Answer
This may not be enough. A discharged battery has higher internal resistance, the voltage drop can be much bigger than 200mV depending on load current and battery chemistry.
Some sort of latch is probably a good idea, but keep in ming that this circuit should consume as little current as possible - otherwise the battery might get damaged in under-voltage condition.