TP4056 3V3 load share addon board

The cheap TP4056 Li-Ion charger boards need some upgrade

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I wanted to have a load sharing for my future battery operated project with the ability to charge the battery. There is a load of cheap TP4056 boards from China. None of them has the load sharing or voltage regulator on board so I made my own addon board.

Schematic was inspired by various schemes from internet forums (TODO links).


load sharing - when the Vcc is present the battery is charged and it is cut off from the load (by the Q1) while the load is powered from Vcc (via D1). When there is no Vcc the load is connected through the Q1 with the battery. Contacts LOAD are for "raw output" without the voltage regulator.

The advantage of MCP1252 is automatic buck/boost feature, it will maintain the regulated output voltage whether the input voltage is above or below the output voltage (2.1 to 5.0V input range) so it is ideal for the lithium battery voltage.

If you read the datasheet for the MCP1252-33X50I/MS there is clearly specified what type of MLCC capacitor should be used.

The PCB layout was heavily inspired by MCP1252 datasheet.

Output parameters are:

  • max. output current 120 mA
  • output voltage 3.3 V

There is also a MCP1253 which is identical to MCP1252 but has higher switching frequency (1MHz).

  • 1 × MCP125233X50IMS Power Management ICs / Switching Regulators and Controllers
  • 1 × FDN304P Discrete Semiconductors / Diode-Transistor Modules
  • 1 × SGL1-40-DIO Shottky diode
  • 2 × 100k 1206 resistor Electronic Components / Misc. Electronic Components
  • 3 × 10uF 1206 capacitor X7R capacitor

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  • Assembly

    Robert12/25/2016 at 15:13 0 comments

    First PCB was assembled few days ago. So far it looks like it is working but I still have to make some measurements to confirm it. I haven't tried it with the battery, only with variable voltage source.

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topher217 wrote 11/21/2018 at 08:19 point

Thanks for the walkthrough! I'm thinking of replicating the load sharing behavior but with some other voltage regulator and had a few questions for you.

What's the purpose of adding C1 and C2? In the MCP1252 datasheet they mention C_IN for filtering noise and ripple, but aren't such capacitors included in the TP4056 board already? I can't seem to find a schematic of the board but I see a few capacitors on there, and wondered if they are already equipped or not. If they are already on the TP4056 board, then is there some other reason you found in order to motivate them being there?

Also, shouldn't the transistor be a depletion type rather than the enhancement type shown? Otherwise the transistor would be normally off and turn ON when the VCC is applied, leading to both VCC and the battery connected to load. Don't you want the battery to power the load when VCC is OFF and VCC to power the load when ON?

  Are you sure? yes | no

ma wrote 01/19/2017 at 06:19 point

Can you help me understand how load sharing currently works? The TP4056 boards already allow a load to be connected along with a battery and have power in. Can you explain the difference with this board? And is it an extension of the TP4056 board or a replacement?


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Robert wrote 01/21/2017 at 15:40 point

When external voltage is connected to V+ and V- the battery is cut off the load circuit. Voltage regulator is powered from external voltage and battery is charger from external voltage without any load.

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deʃhipu wrote 01/06/2017 at 12:23 point

This looks super-useful, however, with 120mA you can't even power an ESP8266 with it, not to mention a display or a servo... What kind of projects do you have in mind for it?

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Robert wrote 01/06/2017 at 14:16 point

You are absolutely right with ESP8266 but I didn't even think about anything like that. I plan to use it with CO2 sensor (about 30 mA) and other low power sensors, some MCU (teensy or something simillar) and LCD. I should fit into 100 mA easily.

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ThantiK wrote 12/31/2016 at 17:25 point

Would something like this support solar charging as well?

  Are you sure? yes | no

Robert wrote 12/31/2016 at 18:04 point

It depends on what you expect. I have no experience in solar charging but if you google "TP4056 solar" you can find some projects using the TP4056 charging board. All I did on top of that is adding the load sharing (when the Vcc is present the battery is charged and it is cut off from the load while load is powered from Vcc) and voltage regulation using MCP1252.

  Are you sure? yes | no

chaz wrote 02/08/2017 at 11:05 point

I'm going to try this on a solar charged project. BTW the diode is obsolete and not available , I will find a sub.

  Are you sure? yes | no

Robert wrote 02/28/2017 at 23:36 point

@chaz that is good to hear let us know your results when you try it please. :)

I didn't know about the shottky. I am still able to buy it from my local (european) dealer.

  Are you sure? yes | no

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