I have a factory stock EB236 controller board and also a spare board for it. I decided to build the spare board into a 36 FET IRFB4115 controller so to play around with. I also wanted to do the same buss bar mod to it that I did on my EB318 controller I got from Lyen which now takes up to 12kW and regularly handles 10kW of input when I ride on 30S2P or 30S3P LiPo charged to 125V.
So here are the pictures of my progress.
First up is the size comparison so you can see exactly how big this is.
On the top is a normal 18 FET controller
The next one down is a 24 FET controller
The last one is the 36 FET controller which uses the same case style as the 24 FET, but just longer to accommodate the extra FETs
Very bottom is the internals of the 36 FET controller with parts setup for 60V max. I have the heat sinks removed. The coil of wire is the silicone multi stranded 6 gauge wire that will be connecting this controller to the batteries. All phase outputs will be 8 gauge.
Next up is the construction of the buss bars for each bank of FETs. The construction of all 6 of these took about 4 hours. Had to take the #6 eyelets, cut off the plastic, then pull them apart so they were flat instead of round and tin them with solder and make sure I got the spacing as close as possible. Buss bar is sold 8 gauge copper grounding wire picked up from the hardware store for 93¢ per foot so I nabbed 10 ft of it along with 4 ft of 6 gauge... just in case I need to beef up a trace somewhere and go over board. I also have the FETs separated into groups of 6 matched by Miller Plateau resistance. I'm trying to keep them all as close as possible in each back so that they will current share better.
This is the buss bars heat shrinked to insulate them against shorts to the heat sink / spreader bar. FETs still groups waiting to be installed.
One side completed. Decided to use the nylon screws again because I've had such great luck with them on my 18 FET which is being abused regularly and they are holding up great. They have a continuous operating temperature of 188C. Only downside is that you can't crank down on them with as much force as metal screws, but that doesn't seem to be much of an issue in my EB318 using the same mod since I'm always monitoring the temperature.
For the insulators I decided to scrap the stock ones (not sure if they are Kapton or not, but they seem rather ragged, have thermal paste on them and I don't trust them) try some Wakefield 173-7-220P insulators which are rated at 0.33°C/W 12.6 W/m-K. Not sure how well they will work but wanted to give them a shot.
The fasteners are a #6 3/4" nylon screw with a #6 brass washer, the buss bar made from #6 eyelets, the FET, the Wakefield insulator, heat sink spreader bar, bronze lock washer and finally a #6 brass nut holding it all together. I went with brass and bronze fasteners to hopefully help increase the thermal mass on each FET's tab and allow it some more time before it heats up too much. Past experience with my 18 FET shows me my buss bars really help soak up some of the extra heat and they aren't even as good as this 8 gauge solid copper wire on this setup.
That's it for now. I should have the other side mounted up tomorrow and start construction on the board by adding the caps/transistors/etc to it. If this one works out well I'll cut down the factory board in the first pic, rebuild it for 150V use and put it into a custom black Hammond case with shorter alum buss bars mounted to the case much like the stock setup is. All assuming I have time and will to do it. Wanted to get this build going first for when I get my 13kV motor, next up is most likely one of my water cooled TO-247 power sections. Got plenty of controllers to play around with in the future
Greyborg Hub Motor, Lyen 18FET, Customized full suspension kids MTB. Top Speed 61 MPH
9C 8x8, 24S2P LiPo, Lyen 12 FET, Diamondback Recoil Comp. Top Speed 42 MPH