300A VESC in the works, feature suggestions wanted

[TechAUmNu]

Any preference on connector/wire size?

Thinking either 8mm or 10mm bullets on the board or short (<10cm) single 6AWG or dual 8AWG cable.

Was thinking it would be nice if they could bolt together in a stack and have a parallel bus bar that can run between them to cut down on cables. Then a single cable can connect them to the battery. (Or at least that is what I want for Triforce due to the limited space) This option would require to use bullets soldered to the pcb to be practical.

[overkill]

bullet connectors are handy or copper lugs like the big Kontronik ESCs:



They are slower to work with but very reliable.

[TechAUmNu]

That looks really nice! Only problem with lugs is they are relatively heavy for the surface area, and you then have quite a long connection since the lug has to protrude from the case.

[shakesc]

I do like the copper lugs

[Pinski1]

I mean: ESC +5V (+diode drop) -> diode -> external +5V. As found on some VESCs and Ragebridges.

[overkill]

I can't argue about the weight or size, but they are ultra reliable and can actually reduce surface area in other places if you do it right. Having the lugs laser cut to fit your PCB tracks means you can reduce their widths as the lugs are providing the current capacity from the FETs.

[TechAUmNu]

I am putting on laser cut copper plate a few mm thick for all the high current areas + 4oz copper on the pcb. Then the heatsink contacts with them through a thermal pad. Most of the heat will be dissipated through that. Which lets me put the FETs back to back and reduce the overall size of the board significantly.

[TechAUmNu]

Have now switched to some Fairchild fets instead and dropped the voltage to 80v. This lets me get significantly less power dissipation and hopefully higher currents. (psst They are also a LOT cheaper...)

http://www.mouser.co.uk/Search/Produ...-FDBL86361F085

Will be finishing up PCB this week and then getting a few made up for initial testing.

[overkill]

The specs on those new FETs look great and quantity prices of $4 and below are amazing for a high current FET - its looking very promising! Can you give us a hint on the likely PCB size yet?

[TechAUmNu]

Yeah they are pretty sweet.

I need to test out thermals first before i can settle on a board size, but it should end up roughly 60x100mm
Might be smaller if it can handle it.

[Ellis]

Looking forward to this. FWIW, despite loving compactness as much as anyone, I'd rather have a big ESC that can handle this kind of demand for real (my weapon motor peaks over 300a, though VESC-level efficiency should rein that in). 20% bigger but 20% better thermals is totally worth it at this point. I'm very bored with ESCs that just can't.

Let me know if you need a test system that will happily murder ESCs on demand!

[TechAUmNu]

Looking forward to this. FWIW, despite loving compactness as much as anyone, I'd rather have a big ESC that can handle this kind of demand for real (my weapon motor peaks over 300a, though VESC-level efficiency should rein that in). 20% bigger but 20% better thermals is totally worth it at this point. I'm very bored with ESCs that just can't.

Let me know if you need a test system that will happily murder ESCs on demand!

Ok I will make it a bit bigger then, would you object to a small fan to let me push it to the limit? Since these fets are also much much cheaper I could bump up to a 36 fet design again for a £45 increase in BOM cost to £150. That would handle 400A with a 100W dissipation on each phase. At 300A its 50W per phase.

[Ellis]

Actually, though I don't have direct experience, fans (assuming fairly standard computer-style fans) always seem to break in combat. They can't handle the shock forces. I'd be inclined to avoid them if possible. The nature of modern compact machines is such that they'd probably be smothered to the point of being ineffective anyway.

In terms of power, it depends on realism. If the 300a setup can truly do 300a, as in, pulling anything up to 300a in a 3 minute fight absolutely cannot kill it, then that's fine. That'd give a weapon 15kw to play with on 12s, which combined with efficient control is plenty for a top heavyweight.

The issue is that the vast majority of hobby level ESCs simply can't do what they claim, and that's infinitely frustrating and getting old very fast. So far it seems the only products on the market that truly, reliably do what they claim come from MGM. The top Kontroniks maybe too. So we don't need another 3-400a esc that will blow at 200a for a few seconds - do whatever you need to do to get beyond "hobby amp" ratings within reasonable cost and you'll be very popular!

[TechAUmNu]

OK in that case I will make sure it can 100% handle 300A with no issues. At the 16s maximum it would be 20kW which should be plenty for any of the motors I have seen.

I have 3 of the Fatboy V2 boards which are frankly a joke in comparison to what I have so far. However we didn't manage to blow them up... yet.

Once I have got this board layout finished and got some in and tested to make sure they don't instantly explode I will probably send one to you and Rory to test out.

[overkill]

I 100% agree with Ellis about fans - they always break no matter what their construction or price point. I have tried plenty of modifications but it hardly helps.