question

Every PWM regulator contains a inductor what is matched to the PWM frequency and what delays the current after Mosfet switches on. Its the basic task of any pwm regulator to switch off when the required charging current has been reached. Otherwhile it also wouldnt work with any solar panels for source.

The MPPT feature would be useless as the voltage of a source battery hardly drops with its load. Anyway it should work as well but MPPT is only useful for for low iluminated panels.

Probably we should ask our friend Johannes Boonstra to make a YT video “inside PWM“ like there is one with „Inside Multiplus“. Anyway I bought a BlueSolarPWM 48-30 to disasemble myself and see how the things work.

Instead of an inductor for current regulation I found many N-channel Hexfets and no inductor for the PV charge current. The regulator considers the PV module as a current source rather than a voltage source. As a current source is short circuit proof by design, it can be connected directly to the battery. The charge current starts and battery voltage increases. This is equivalent to the current what would go up e-curved inside a regulator design using inductors. To switch off, the Mosfets interrupt the battery connection and short circuit the solar panel. The battery voltage goes back e-curved like the currents in inductors do. PWM frequency and pulse width is not like expected in khz range for ferrite magnetics but determined very slow by the battery chemistry. Using a shunt, the uC is able to calculate the battery resistance and exact charge state.

For the reason that PV modules are considered as a current source what is switched off with a short circuit, all solar regulators seems to have a maximum allowed short circuit current in the data sheet. User should avoid connecting other sources than PV modules according to the manuals. Johannes Boonstra: Pls make a YT video to shed some light on this.