Searching for LiPo chargers, I came across this 1A Lithium Battery Charging Lipo charger embarks Module DIY Mini USB Port PK, for 99p, and I wondered how easy it would be to build a DIY LiPo charger.
TL;DR – Unfortunately, while this device is good for a single cell battery, it is of no use for multiple series cell batteries (2S, 3S, etc.), as the links at the bottom show.
Again Julian Ilett has a couple of great videos of youtube
Charging a Lithium 18650 Cell using the TP4056
and the improved New TP4056 Lithium Cell Charger Module with Battery Protection
A useful video, DIY: Lithium 18650 Cells Charger By Using TP4056 Modules, to build this five cell charger
However, none of the videos above address the issue of constructing a multi cell LiPo battery. The links below are to threads that approach the problem:
Using a TP4056 to charge a multiple cell (more than 1S) LiPo
This method is not viable. See this answer.
The disadvantage of your concept charger is that each unit will need floating supplies.
That is they cannot share a common ground.
This is not the best way to charge Lithium batteries in series, charging possible with 2 extra DC/DC isolated converters, which is ridiculous. If every cell at good condition they will charge to charger’s default charging cap (TP4056 tries to get 4.2v). But these cheap ICs not good at it, and you will end up un-balanced battery block, which will cause batteries quickly wear out. Not efficient, nor safe. Do NOT risk trying to do that. Simply get Lithium charger with balance.