Hi Timothee, when driving large current loads you want to do several things. The first is to minimise the Rds (on resistance) of the FETs, the FETs I suggested have a much lower Rds than the IRFZ44, so less heat produced when fully conducting.

The next thing you want to do is minimise the switching time, which is the time from non-conducting to fully conducting, and back again. This is the linear region and the FET has a much higher resistance when in this region, so more heat produced, albeit for a short time period. To minimise this transition time you need FETs with as low a gate capacitance as possible (gate capacitance slows transition time because the gate has to be charged and discharged each time the FET is switched) and you also need to be able to drive the gate with a decent current level to charge and discharge it rapidly (as someone else here mentioned).

So, a single FET with the appropriate specs will have a lower gate capacitance than multiple parallel less-capable FETs (most likely), but you need to check the specs sheets and go from there. A FET gate driver is a good idea, as someone else mentioned, but I've generally found at lower switching frequencies that it is less necessary as the FET will still spend most of its time fully on or fully off.

So, I would look at a beefier FET, one designed specifically for this sort of use, and if that doesn't solve it then add in a FET gate driver to speed up the switching.

Hi Boggart,

Wow such simple words yet so effective, thank you for summarizing it all, i feel like I KNOW how to drive mosfets now ! I'm do this asap and let you guys know how it went I would like to sincerely thank every single one of you for your patience and time this has helped me so much in understanding electronics. I'll see you guys around.

Timothee

 

Hello there,

Not sure if anyone mentioned this yet but, for circuits like this it is also typical to employ some sort of current limit. That's in case the output tries to draw more current than the circuit is was designed to be able to handle.
If your circuit is designed to handle 80 amps and it suddenly gets a load that looks like three times higher than that, something is going to blow out. If the circuit can current limit at 90 amps, it's going to work much better.
If the motor(s) can not start up at that 90 amps for some reason, then you need to design for a much higher current than 80 amps.

What are those 1N4004 diodes doing? I am not sure what the max switching frequency is, but if it is above about 400Hz you should use Schottky diodes or just some other high speed diodes. Regular rectifier diodes are made for frequencies like 60Hz. At higher frequencies they can really screw things up.

 

Hello there,

Not sure if anyone mentioned this yet but, for circuits like this it is also typical to employ some sort of current limit. That's in case the output tries to draw more current than the circuit is was designed to be able to handle.
If your circuit is designed to handle 80 amps and it suddenly gets a load that looks like three times higher than that, something is going to blow out. If the circuit can current limit at 90 amps, it's going to work much better.
If the motor(s) can not start up at that 90 amps for some reason, then you need to design for a much higher current than 80 amps.

What are those 1N4004 diodes doing? I am not sure what the max switching frequency is, but if it is above about 400Hz you should use Schottky diodes or just some other high speed diodes. Regular rectifier diodes are made for frequencies like 60Hz. At higher frequencies they can really screw things up.

Hi there Mr AI,

Yes someone mentioned it i think, but what kind of component or circuit is used to limit the current to a fixed amount ? Yes those 1N4004 are not suitable i will change them for shottky diodes ! Thanks a lot for the tips
Timothee

 

Hi there Mr AI,

Yes someone mentioned it i think, but what kind of component or circuit is used to limit the current to a fixed amount ? Yes those 1N4004 are not suitable i will change them for shottky diodes ! Thanks a lot for the tips
Timothee

Hi,

Well, you could look into a simple resistor shunt type current sensor to provide feedback to the control circuit, or look into magnetic based sensors like Hall Effect sensors to provide feedback. If a high current is detected, the control circuit cuts it back to a non-destructive level.
The type of control could be linear progressive, or fold-back where the current is decreased and kept like that until the current is detected as being much, much lower, which means someone has intervened and corrected the problem.

 

Sorry but your link doesnt work im curious to see what you sent me !

Yes, that listing is gone now. If you search ebay for 60A DC 10-50v 12V 24V 48V 3000W DC Motor Speed fan Control PWM HHO RC Controller you'll find what look like the same things.