I am aware that a solar panel has a fixed IV curve, and the load resistance can move the operating point of the solar panel along the IV curve. If a solar panel was used to directly charge a battery without MPPT(I know this is bad practice cuz we need charge controllers, BMS and voltage regulators, but IF!), where would the operating point of the solar panel be? Here, would the internal resistance of the battery be the load resistance? But the internal resistance of battery are very low, in 0-100 milliohms (for example for phone batteries).
Would this mean that the circuit (battery and solar panel connected) would be like a short circuit? Then, would that mean that the voltage of the solar panel is close to 0V and current will be close to the short circuit current, resulting in almost 0 power? If that is the case, then wouldn't adding a 5V buck boost converter not help charging the battery since despite the voltage being 5V (if the input voltage is higher than minimum input voltage), the current will be so low?
If my way of thinking is correct, then how are there so many tutorials on solar chargers which state using an appropriate power solar panel, 5V buck boost converter and a USB port is enough for charging a phone?
Please correct me!