[GriffinRU]

Originally Posted by lutach

What I meant to say about the FETs is if they are old with high resistance, would it be better to go with a lower resistance one? Also, a bit off topic, but I keep forgeting to ask you. What is the advantage of adding more FETs to a controller? What needs to be changed? I'm having a hard time trying to figure this out. I've seen many 3-4 board ESC use the same FET driver as a single and double board one. I know there are drivers out there that can put out 3-8A, but what is actually needed to open a lot of FETs? I use a MOSFET Driver Calculator made by Microchip, but it only uses a few simple numbers that can be found on a FET datasheet. It doesn't give an option for multiple FETs though.

BrianG

Microchip calc good tool, but you need to use it multiple times to cover full duty cycle. More fets -> add total gate charge and capacitance, but be aware that fet's parameters are dependent on load. This tool helps to calculate driver for fixed circuits like DC-DC convertors. In addition to verify high side, in H-Bridge, you need to calculate bootstraps diode and caps parameters. As well as rated gate voltage and drives power supply requirements. Then to minimize ringing in mutifets applications you need to add series gate resistor and do the calc again.
In general it is not that bad once you get the entire picture, but can be complex to estimate working parameters across all temps, loads and fets.

P.S. More fets -> it’s like more micro switches which can split the task, but the most important task would be to keep them synchronized!!! And that can be lost quite easy, you've seen plenty of smoke...
It is like single strand in multi-strand wire...