Why does the TP4056 charger not start charging after being discharged?

Question

Batteries

Hi all! There is a classic scheme: TP4056 charger + DC-DC step up converter. A 10W solar panel is connected to the charger. The essence of the problem - when the plug-in device to the converter completely discharges the battery, then even connecting an external power supply to the charger does not lead to charging the battery. In theory, the battery should charge to 3V with a small current, and then the charge will start with a large current (about 1000 mA) and the discharge protection will turn off and the supply voltage will appear on the converter. But the battery does NOT charge up to 3V even after 10 hours, while the charge current does not rise above 80 mA. When the device that needs to be powered is disconnected from the converter, after a while the battery starts charging. But I need the discharge-charge cycles to occur automatically without breaking the circuit. What could be the problem? How to fix?

Answer 1

charging in the presence of a battery and its low charge charges with a small current to a certain level and only then gives a "full" current.
the converter turns on and keeps working below the level when the full current from charging is turned on. as a result, the converter lands the battery, charging sees that the battery is "dead" and reduces the current to the minimum value => everything turns off.
with this set of modules, this is no cancer and under no circumstances can be solved - the modules are excellent and this is precisely the problem.
The solution is to find a charger that does not know how to "trickle charge", look at the datasheets. either find a converter that itself is forcibly turned off at an input voltage of ~ 3.1-3.2 V. or blind an external shutdown circuit for a given threshold.