How to force the FS312F (DW01A-G) battery protection IC to automatically enable itself when reaching the overdischarge release voltage or above

Question

The IC successfully cuts off the battery when the voltage goes below 2.9V (2.4V with DW01-G), but it doesn't reactivate itself when it is reaching its overdischarge release voltage. I would like to add some logic which is monitoring the voltage level of the battery and reactivating the circuitry by enabling the discharge mosfet trhough the chip select pin.

Another problem which would be solved by such a solution is the necessity of plugging in a charger, when connecting a fully charged battery for the first time to the circuitry in order to make it running. You can find a note for this case in the datasheet:

I ended up with the following shematic, where the CS (chip select) pin is pulled to ground by a 3904 NPN transistor as soon as the MAX809S voltage detector (reset/supervisor/monitor) IC is getting triggered - means the reset pin is set to HIGH at 3.2V or above, which is the case with a fully chared battery. This should have the positve effect that the circuitry is directly working without the need of plugging in the charger after inserting a battery for the first time in order to make it running.

Updated due to comments:

Like mentioned in the comments this is not working because U1 and Q1 are controlling the path to BAT- and thus there is no correct voltage measuring possible.

Here is a new try: I replaced the 3904 NPN transistor with a N-Channel Mosfet to reduce the current draw and connected it directly to the Battery, while respecting the battery cell reverse connection protection (Q2):

Any concerns about this new one?

1. maybe it is still not the right way to do or
2. maybe I should add some resistors somewhere or
3. maybe it is still drawing too much current or
4. maybe it is even dangerous, because this is bypassing some important safety features?

Answer 1

From the datasheet the DW01A has "AUTO recovery" from standby mode. In other words the battery can be discharged again once it rises above the release voltage.

That's probably why the problem isn't commonly reported by people using those popular little TP4056 + DW01A boards as is.

FS312F has no auto recovery. The FS312MH does have auto recovery according to datasheet.

I know your question was basically to design a circuit that will short CS pin to ground when overdischarge is reached. This is beyond my capability but I had to answer the mystery about why this question seems a bit obscure. Probably not many have bothered to switch from the commonly used DW01A to FS312F thus running into this issue.

Answer 2

With N-Channel MOSFET Drain and Source between CS and VBAT- and also pull-down resistor between its Gate and VBAT-. You need a single pulse to turn on the Gate to short the pins.

One way to do that is with output of RC HPF with input from BAT pin. Make sure the ground of that HPF is BAT-. Adjust the value with trimmers so that the timing could turn on the gate properly.

The R in that HPF could also act as pull-down resistor. So in the end you just need 3 components to accomplish this, MOSFET, R and C.

It is stable because it's a single pulse right at the moment you insert the battery. If the battery is really below the overdischarge detection voltage then the IC still won't turn on the gate of that common-drain back-to-back MOSFET. So there won't be any oscillations.