Hi,

I am trying to understand this little USB-C module, for the charging & discharfing of small lithium batteries.

From what I am reading the TP4056 will take a power input through it's USB-C port, and use this to safely charge batteries connected across the terminals. However, if this 'charged array' of TP4056 + batteries is connected to another USB-C, this time to power the connected device, will the TP4056 do power delivery too?

If not, what is the suitable 'two-way' module, where the TP4056 is only one-way?

Also, I'm reading that the TP4056 cannot be attached to a battery(ies) of less-than 1000mAh size. Accepting that this is so, is there another board/module that might dseal with much smaller battery-arrays, in the 50-100mAh range? - again, with the 'two-way', charge-discharge function.

Lastly, I am not sure what sort of 'mains-power' device one would use to 'charge my hypothetical charger' safely, under what the USB-C standard allows - if I understand correctly, the 'PD' bit of the USB-C standard means that 'any' device with charging funtionality would be able to charge it, the inverter AC-to-DC and current control being upstream of this device charging... I hope this isn't too unclear (!),

Thanks, Damian

 

Welcome to AAC.

The TP4056 does not allow provide a facility for using the cell*, only for charging it. The TP4056 is an IC, not the module itself. To use the cell to provide power, you will either need a module that uses the TP4056 or a similar chip, and provides a boost converter to take the ~3.7V (4.2—~3.2V when discharged) cell output and boost it to 5V.

*Although it is very common to call a single cell a battery, there is an important distinction concerning the technicalities of using them, and particularly charging them. It is best to use "cell" for a single cell and "battery" for an electrically connected group of cells when having a discussion about charging and otherwise managing a single cell to avoid confusion. It turns out the name "battery" came from Ben Franklin who likened a group of cells to a battery of artillery in the way it multiplied the power.

The common 1A TP4056 module looks like this:

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The red circle indicates \( \mathsf{R_{PROG}} \), a resistor that determine charge current. It usually comes populated with a 1.2㏀ resistor but you can change it to get whatever current you want, according to this table which comes from the TP4056 datasheet:

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If you zoom in you will see the resistor is marked "122", this is the standard code for marking surface mount resistors and is easy to decode. The "12" are the significant digits and the "2" is the number of zeros—so "122" is 1200Ω, which is 1.2㏀.

The lower bound on cell capacity is driven by the charge current and the specifications provided by the manufacturer. The charge rate is generally 1C, where "C" is the capacity of the cell in ㎃h and the "1" is a multiplier. So if you had a 500㎃h cell, you could choose a value between 2㏀ and 3㏀ to get a good charge rate.

As far as PD, while I know of boards that can charge a cell and then provide power with an on-board boost converter to 5V or 9V or 12V depending on your needs, they don't have Type-C connectors (or any, for that matter.

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You could use one of these with a Type-C connector negotiate a 5V charging power from a PD compliant charger, but you can't have the cell providing power back out that same connector.

There are two pads marked "R1" on the underside of the PCB (left). They are for a pull-down resistor (56㏀)
to tell the charger you want 5V@1A. You don't have to use that much current but that will be available.​

You would have an input and an output. Type-C pigtails are readily available, and it could be connected to the Load terminals—but there would be no negotiation and that might cause some things not to work.

It would help a lot if you'd describe the application of this device because the details that accompany such a description will help a lot in providing practical advice. It will save a lot of random dead ends and questioning.