I was just reading adding heatsinks to the top of the fets almost does nothing. According to Rew:
"Yes. Note that cooling the “top” of the fets (the side you can see without desoldering) is useless. I’ve found a datasheet that mentions 10x the thermal resistance to that side of the case than to the side that you’re planning on cooling. Note that the high-side-FET drains are all connected to “VMOT”. So you can easily solder all three of them to a big copper plate (connect to VMOT as well!) and a heatsink.
On the other side, the three drains are connected to the motor phases. So you’d need an L-shaped copper conductor and then an insulated heatsink on that. Consider: There is also the IRFP7530. The problem is that it is a lot bigger: TO247."
Also the temp sensors aren’t really on the fets just nearby and there’s really only one sensor for all the fets for now
I showed you real world tests hummie… I have one right now with a heatsink and one with out (both chakas). The one with the heat sink draws more amps than the one without the heatsink. They both get to about the same temperature, but the one with the heatsink cools quicker, and thus can pull more amps than the one without the heatsink.
Without heatsinks, I had heating issues with my carvons. With heatsinks, the heating issues went away. My real world tests show me that the heatsinks do have a positive effect of dissipating heat.
I haven’t done any tests and I never get too hot but I thought it was worth noting what the resident expert on vedder’s site said given so many people have problems.
i know they have a plastic case and it’s hard to really get to the source of the heat.
I think some people try to mask actual problems by adding heatsinks. I dont think it’s to say heatsinks are useless, but rather they’re not always the best way to solve a heat issue.
In my experience they can be pretty well contained but others have had problems and need to add heatsinks and get better airflow.
I’m not saying a heatsink on the top does nothing just bringing a point of view from someone who knows a lot and we could maybe further benefit from what he’s saying
This is something I have been intending to create once our mill is up an running. It will be interesting to see if it increases the capability of the VESC with a more direct connection to the base of the fets.
I think a low amp, high voltage system likely dose not need heatsinks if the motor/gearing is efficient. I needed them, because they way I was running my carvons was not efficient, I never got close to 85% of my no load speed, as that would be way too fast. With your motors even @Hummie, the heat sinks had a positive effect. You never had issues because you have good airflow i.e. they are duct tapped to the bottom of your board. But if you enclose them, they will get hot.
actually theyre pretty contained in bubble wrap and tape these days and cant be seen. wish my batteries were as well as they’re all dying from shrapnel again.
the no-load speed is constantly changing based on your throttle and what percent it sends to the motor of the battery voltage and if your motors are big enough and the load not too big they will be near it. the carvon are big and you probably were. I think more the reason carvon get the vesc hot is because theyre such high kv it takes more amps for them to create torque.
i think heat and electricity conductibility go pretty hand in hand except for some fancy pastes and silicones.
chaka is that dangerous is that why you dont want that? to touch? what on the board is dangerous to touch at 12s? Have you touched 12s!? I mean possibly shorted across something with 50v. had your body in circuit with that and you dont zing
