Maker Pro
Maker Pro

TP4056 Load output if possible to connect in series

DMTVK

Mar 2, 2022
8
Joined
Mar 2, 2022
Messages
8
Hello everyone,
I have a small project to do which is preparing something similar to an automatic emergency light.
I have purchased 2 TP4056 charging circuit boards with two 18650 batteries and a P channel Mosfet.
My load is a 6V LED board. any suggestions on how to do the connections?

I want to try and connect each TP4056 board separately to an 18650 battery ( for charging) with a common 5V input. then the outputs of each board to be connected in series to later lower the voltage to 6V using two resistors 10k and 24k.

Can you please confirm if my circuit will work that way or should I be using some other solution?
 

Harald Kapp

Moderator
Moderator
Nov 17, 2011
12,615
Joined
Nov 17, 2011
Messages
12,615
Can you please confirm if my circuit will work that way or should I be using some other solution?
I can confirm that this will not work. Input of the TP4056 and "-" of the battery are common. Thus your scheme will create a short circuit between one of the batteries.
to later lower the voltage to 6V using two resistors 10k and 24k.
This is a rather high impedance voltage divider. You will not be able to draw any useable current from this divider. As soon as you draw current, the output voltage will drop drastically.
should I be using some other solution?
Definitely. Use one TPS as charger for a single battery. Then use a step-up converter to create 6 V from the cell voltage. Such modules are readily available.
One note however: Make sure the step-up regulator is designed for Lithium cells with an undervoltage protection. To prevent deep-discharge of the battery the load needs to be disconnected from the battery once the voltage falls under a critical threshold.

You may be better off using a power bank module (example) which charges a battery and output 5 V. By tweaking a resistor such a module should be able to produce 6 V instead of 5 V, too. But make sure you remove the USB-A conector in this case to prevent accidentally applying 6 V to a standard USB-device which will tolerate only 5 V.
 

DMTVK

Mar 2, 2022
8
Joined
Mar 2, 2022
Messages
8
step-up regulator like the MT3608? I will try to get it but I was trying to make use of what I have.
Another question... might a diode prevent the short circuit issue if placed on the circuit input (5V) and load output (4.2V)?
 

DMTVK

Mar 2, 2022
8
Joined
Mar 2, 2022
Messages
8
Then use a step-up converter to create 6 V from the cell voltage. Such modules are readily available. One note however: Make sure the step-up regulator is designed for Lithium cells with an undervoltage protection. To prevent deep-discharge of the battery the load needs to be disconnected from the battery once the voltage falls under a critical threshold.

Hello again, I finished the project and thanks to you after suggesting the step up converter.

Everything worked out fine, but there are two things that I need to ask about.

1- The TP4056 charging module is making a buzzing sound. ( is it normal?, or something needs to be done to reduce any noise in the circuit)

2- When the AC input is cut out, the LED Board slowly lights up (takes almost 5-7 seconds to become fully bright). ( I have installed a p-channel Mosfet for this action).

Thanks again
 

Harald Kapp

Moderator
Moderator
Nov 17, 2011
12,615
Joined
Nov 17, 2011
Messages
12,615
1: Many switch mode regulators can make a buzzing sound. Afaik that happens when the switch frequency is in the audio range and the coils are not very tightly wound. You can try some superglue on the coil, this may reduce the buzzing.
2: Show us the circuit diagram. The verbal description is insufficient for understanding what may be going on.
 

DMTVK

Mar 2, 2022
8
Joined
Mar 2, 2022
Messages
8
I don't have an actual diagram that I followed but let me try and explain:

1- Load (LED Board) connected to the middle of the mosfet.
2- +ve source 6V (from the step up converter) connected to the right side of mosfet.
3- Left side connected to the +ve 5V output of the phone charger with a diode.

in brief:
I have a 5V phone charger connected to the TP4056 Charging Module ( which is connected to the Battery18650).
The TP4056 is also connected to the to the MT3608 step up converter.
The LED Board is connected to the -ve output of the converter (directly) and the +ve side to the middle terminal of the mosfet.
Then the right terminal (of the mosfet) is connected to the +ve output of the converter ( working at 6V)
Then finally the left terminal (of the mosfet) is connected to the +ve output of the 5V phone Charger.

I hope it is clear. If not not I can try and draw it.

Thanks!!
 

Harald Kapp

Moderator
Moderator
Nov 17, 2011
12,615
Joined
Nov 17, 2011
Messages
12,615
MOSFET:
- Type? NMOS, PMOS?
- Source, Drain, Gate? Please label the pins.

What is the intention of using the MOSFET?
Which purpose has the diode?
 

DMTVK

Mar 2, 2022
8
Joined
Mar 2, 2022
Messages
8
Type: P-channel Mosfet
Source: 6V from +ve terminal of Converter
Drain: LED Board
Gate: 5V from the +ve terminal of the phone charger

and the Diode was installed for safety reasons nothing more (I can just remove it).Automatic Emergency Light.jpg
 

Harald Kapp

Moderator
Moderator
Nov 17, 2011
12,615
Joined
Nov 17, 2011
Messages
12,615
It seems what you want to achieve is that the LED is turned on when AC power fails. To do that, you need to pull VSUBgsof the PMOSFET negative. Since teh source is at + 6V, this can be done by applying a gate voltage < 6 V. Pulling gate to GND (0 V= would be the obvious way here. Assuming Vgsth of the PMOSFET is > -6 V (e.g. -3 V logic level MOSFET).

the mosfet is being used as a switch.
No, it is not. At least not in your configuration. You do not provide a means to pull the gate low. Therefore the floating gate will drift slowly when no mains is present (or to be precise when no voltage from the AC adapter is present). The floating gate creates the non-switch action and slowly turn the LED on.
Add a resistor from the gate to GND, e.g. 1 kΩ to pull the gate to a defined low voltage level.

The diode is not required.
 
Top