TP4056 Li-ion charging and protection board

[santoshgurral]

Hi

I have a doubt regarding the TP4056 Li-ion charging and protection module. Attached the image of this board.
I see there are so many articles and videos on the internet regarding this board that it does not provide overcharge protection(never terminates charging) if a load of more than 100mA is connected to its OUT+ and OUT- terminals while charging. Why is this behavior? How to fix this issue?

As per the TP4056 CC-CV charging IC datasheet it states "The TP4056 automatically terminates the charge cycle when the charge current drops to 1/10th the programmed value after the final float voltage is reached" so if this IC can not terminate charging when the load is >100mA why does not the DW01A IC provide the over-charge protection? because as per DW01A IC datasheet it should. Please see the attached image.

Thanks
Santosh

[SiliconWizard]

This circuit alone is only meant as a battery charger, not as a complete load sharing solution.

As you got correctly (and as is the case with any charger IC that doesn't handle a specific load path), if you connect a load in parallel with the battery, the charger IC has no means of knowing when the charge is over, as it relies on the current falling below 1/10 of the charging current when the charger is in constant voltage mode (last part of the charging cycle.)

Some charger ICs have an additional internal time-out counter, meaning that if the current has not fallen below 1/10 of nominal charging current after a given amount of time, the charging will just stop. I don't know whether the TP4056 has this feature. If it does, it would just shut down the load automatically after a while if said load exceeds the threshold current.

Another issue with this setup is that if your load is not a constant current load, the charging current to the battery will effectively vary over time, which is not optimal either.

Just putting the load in parallel with the battery is a bad idea overall in general and should be done only with extra care. You should preferably add some kind of switch-over circuitry to power a load while charging.

[santoshgurral]

Ok
If TPS4056 IC does not terminate charging? How about DW01A IC why does not it protect from overcharging as it is present on this board?

Thanks
Santosh

[magic]

Normal charging process it to charge the cell up to 4.2V and maintain it at that voltage for a short time, the usual rule being until charging current decreases 10x. After termination of charging, cell voltage quickly falls down some tens of mV even under no load.

I'm not entirely sure but I think that continuing charging at 4.2V for longer time causes slow degradation of the cell. If a TP4056 charger is used with 100mA load connected to the cell, it will keep the cell at 4.2V forever.

DW01A only disconnects the cell if voltage exceeds 4.3V. TP4056 never outputs that kind of voltage.

[Peabody]

The DW01 protects against excessive charging voltage/current.  It does not limit the charging time so long as the charging voltage stays at 4.2V and current is greater than 100mA (or whatever value is determined by the charge current setting resistor).  But a LIPO supplied with 4.2V continuously will eventually swell up and possibly catch fire or explode.

What's needed is an added "load sharing" circuit which supplies the charger and the load separately so charging may properly proceed to shutdown.  The circuit consist of a P-channel mosfet, a diode, and a resistor.  Here's a datasheet that goes into it in detail.  Notice that the mosfet is oriented in an unusual way so the body diode protects the battery from the 5V supply.

http://ww1.microchip.com/downloads/en/AppNotes/01149c.pdf

And attached is a drawing showing such a circuit for a 5V Arduino powered by an 18650.

[santoshgurral]

Thanks @Peabody

So even the 2S or 3S BMS boards(see attached image) can not terminate the charging if the load is >1/10 of the charge current?

Thanks
Santosh

[santoshgurral]

as per the PDF, you shared @Peabody page5 Q1(PMOS) is off and no current flows from the battery to Load. But there is still a path from battery to load through MOSFETs body diode. Please see the attached image. so how is this taken care of? I mean, if there is a current flow through body diode and if that is more than 1/10 of charging current how will charging terminate?

Thanks
Santosh

[Peabody]

So even the 2S or 3S BMS boards(see attached image) can not terminate the charging if the load is >1/10 of the charge current?

I don't know anything about multi-S battery charging.  Maybe someone familiar with those modules can help.

[Peabody]

as per the PDF, you shared @Peabody page5 Q1(PMOS) is off and no current flows from the battery to Load. But there is still a path from battery to load through MOSFETs body diode. Please see the attached image. so how is this taken care of? I mean, if there is a current flow through body diode and if that is more than 1/10 of charging current how will charging terminate?

If USB is not supplying power, the mosfet will always be fully on, so the body diode is bypassed.

If USB *is* supplying power, the mosfet will be off, and the body diode will be reverse biased, so no current will flow through it.  If the charger is putting out 4.2V to the battery, the cathode side of the body diode would have to be less than about 3.6V before any current would flow from the battery to the load.  But the voltage there is about 4.4V (the 5V USB supply minus the .6V drop across the 1N4001).  So, as I say, the body diode is reverse biased.

So basically, the body diode is oriented to prevent the 4.4V from flowing back into the battery when USB is plugged in.  When USB is not plugged in, the mosfet is on and the body diode is bypassed, so it doesn't matter which direction it's pointing.