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I'm building a power distribution board (PDB) for my drone, which is powering 4 ESCs and an Arduino 33 BLE Sense Rev2.

I’m using a 3s LiPo battery which provides 12.6V at max charge. My ESCs are rated at 30A each, but the motors have a maximum draw of 12A each, and the Arduino won't pull more than 100 mA/0.1 A.

On the PDB, I'm including a battery management system (BMS), as I'm using a LiPo, and need to turn it off when one cell goes below 3.1 V (It gets damaged under 3 V, but just to be safe, I'm using 3.1 V). For this I'm using the balance connector (for individual access), the Arduino flight controller, and, most importantly, an IRLB4132 MOSFET, in a TO-220AB/TO-220-3 (They're synonymous). (Mouser link)

Given the 12.6 V and 60 A maximum electrical values (756 W), and ambient and maximum temperatures of 40 °C and 100 °C, respectively, how large would my heatsink need to be?

As a final note, I have 2 MOSFETS, so I could split the load.

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  • \$\begingroup\$ If you are using convection to cool the heatsink then you need to allow for natural air flow around heatsink. What does your enclosure look like? If your heatsink is on the outside of the enclosure, then it could be a burn hazard. \$\endgroup\$
    – Mattman944
    Commented Jun 9 at 0:12

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Your transistor has an Rds(on) of 3.5 mΩ at 10 V Vgs (adjust results for different Vgs), for a power dissipation of 12.6 W at an Ids of 60 A. To limit Tj to 100 C, the Rth(j-a) must be less than 4.76 C/W. Using the given values for Rth(j-c) and Rth(c-s), the heatsink itself must be less than 3.15 C/W. A little too low for the cheap stamped metal sinks, but this is very achievable, especially if you can get some airflow over the heatsink. Specific shapes will depend on your mounting constraints.

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  • \$\begingroup\$ I’m sorry, I forgot to mention, the PCB size is 80x80mm, but I only have 30x30x30 for the heatsink. This could double if I had 2 MOSFETS - 2 heatsinks of the same size. Do you think that it is a viable solution, having two 6.3C/W heatsinks \$\endgroup\$
    – YANNTASTIC5915
    Commented Jun 8 at 16:10
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    \$\begingroup\$ If you have two MOSFETs, the current through each is halved so the resistive losses drop by 75%. In that case, you would need two heatsinks that are lower than 11 C/W, which is probably doable in your size constraints. \$\endgroup\$
    – vir
    Commented Jun 8 at 16:32
  • \$\begingroup\$ Can you recommend a heatsink to me?? \$\endgroup\$
    – YANNTASTIC5915
    Commented Jun 8 at 19:23
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    \$\begingroup\$ I cannot; specific product recommendations are not allowed on this site but since you are already poking around on Mouser, I'll say that they should have several options. Edit: they do in fact have a few heatsinks that fit your thermal and space constraints. \$\endgroup\$
    – vir
    Commented Jun 8 at 19:28
  • \$\begingroup\$ Ok. Thank you vir! \$\endgroup\$
    – YANNTASTIC5915
    Commented Jun 9 at 8:29

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