Has anyone made a circuit that disconnects a single cell lipo when it's voltage gets down to ~3.0V to prevent over-discharge? I'm trying to figure out the best way to do it for the following system (it's only a simple block diagram):
The system can be powered either from the USB port (also used for charging up the lipo) or from the single lipo cell.
The device could be sat unused for a long length of time, and it's possible that the micro in sleep mode eventually discharges the lipo down until it's internal low voltage protection trips. Now that's fine from a safety point of view, but now the battery can not ever be re-charged as the built in protection PCB has disconnected it from the wires connecting it to the circuit.
To try and prevent that I'd like to have an extra layer of protection and disconnect the battery from the circuit at 3.0/3.1V ish. Then there is just the voltage monitor circuit discharging the battery, which should mean the battery doesn't get discharged down to the actually batteries low voltage cut off protection too quickly.
Once in this state, and the battery is disconnected, I'd like it to latch in that state so if the voltage creeps back up with no load on it it doesn't re-connect.
Once the device is plugged into USB again, the circuit will power from USB and the uP will know the battery has been disconnected (battery voltage is monitored by an A2D at the input to the board), so it will reset the latch in the monitor circuit and re-connect the battery so the charger IC can re-charge the battery.
All this is to hopefully stop batteries being damaged when units are not used for a long time.
Has anyone done anything like this?
Thanks,
G