TP4056: Disconnect load while charging and avoid battery discharge below 3v

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danrover

Joined Jan 20, 2020
11
Hello everyone. I would be very grateful if you can help me with this circuit I am working on (sch.png).

It consists of a TP4056 charger connected to a 3.7v/3Ah Lithium Ion battery to supply a low battery level indicator and a load (a block of white leds and two fans), through a MT3608 Step Up to raise voltage from 3.7v to 9v.

As it is in the schematic below, I have a Logic Level P-Mosfet to disconnect the battery from the load while charging (Vin=5v). Also, a diode was added between Gate and Source to make Vg and Vs almost the same (Vgs=0) so the transistor is not polarized.

1) Because of this diode, the load is powered by Vin while charging the battery (Vin=5v, Vg=5v) as it is shown in Photo 2.
Is there any trick that I can do with that P-Mosfet or anything else to prevent the load from being powered?

2) While powering the load with the battery (3.7v). If I choose a Logic Level P Mosfet with Vth=-2.4v (considering: Vgs=0-(Vbat - 0.6v)), can I stop battery discharging at 3v to avoid reaching a lower voltage level and damage it?. By default, TP4056 cut-off discharge at 2.4v, but it is too low for a Li Ion battery.

Thank you so much!

Circuit based on:

https://www.best-microcontroller-projects.com/tp4056.html

https://nomadaselectronicos.wordpress.com/2015/05/22/fuentecargador-con-carga-compartida-load-sharing/

sch.pngPhoto 2.jpg
 
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