Convert PWM solar charge controller to MPTT Charge controller

[inductonator]

What's the difference PWM solar charge controller and MPTT charge controller apart from Firmware ?

Can I write custom firmware for PWM solar charge controller and convert it into MPTT?

Is there anything I need to lookout for ?

[Pineapple Dan]

The PWM one is likely very cheap and nasty and has no inductor or "real" buck converter. There are loads of designs for ""PWM"" charge controller and MPPT. Also a lot of charge controllers have nothing to do with MPPT but some guy in China figured he'd sell more if he wrote those letters on the casing