Low-side MOSFET switching power dissipation

Using Arduino Motors, Mechanics, Power and CNC
1

Hi All,
I have a circuit in which I have an Arduino doing PWM control of a N-channel logic-level MOSFET in the negative side of a 12v battery charging circuit for a solar panel. ie. the MOSFET is between the Solar panel and the battery negative post. It is working all fine, but I had a question about current and heat dissipation.

I know that the current will be the same all around the series circuit (kirchoff's law) but does that mean that the potential difference between the ground of the solar panel and the negative terminal of the battery would be zero? And in which case, does that mean that power dissipation would be minimal?

If you look at the comments of this MOSFET breakout board you can see estimations of 4A being the max the PCB traces could take:

But if I used it on the negative, low-side of my circuit would it be able to take a higher current, e.g. 10A? I know the MOSFET itself would need to be specified to be able to take the current and deal with the power dissipation. I can find one that does and use an appropriate heatsink as well. But I'm not sure what the implications are on the PCB trace size.

Thanks

-Matt

2

but does that mean that the potential difference between the ground of the solar panel and the negative terminal of the battery would be zero?

No.
You look at the potential difference across the device. In this case the voltage between the drain and source.

But if I used it on the negative, low-side of my circuit would it be able to take a higher current, e.g. 10A?

No see above.