neptronix said:
lazarus2405 said:
I have to wonder, what on earth sort of controllers are you folks using to push >100a at >100v?
I'm at the limit of what my Kelly can provide at 90v absolute maximum, and I'd like to get educated on the next steps. 20kw... *whistles*
You need 4115 FETs and lots of them
.. 36 might do!
This motor would eat 4115's by the shovel full. It's heating up 36 irfb4110's so much that I had to install a blower to push fresh air through the controller, and it looks like I really need to add a 2nd blower as well as move the controller to the downtube so it gets full force air flow to the case. I'm seriously considering going to oil cooled. My controller needs it, not my motor. :wink:
I'm not interested in high voltage anyway. The bike does almost 60mph with 20s of sagging 20c lipos, so going just to 24s of less saggy nanotechs would put it past 70mph. That's too fast for me for 2 reasons:
1. I use WOT pretty much only during acceleration. Continuous would only be useful to me on the highway, and even then anything much above 50mph isn't pleasant due to the wind. Give me hard launches and relaxed cruising. I'll leave the high speed to you guys, but if you can't pass the 82mph pedal bike record, then you should be embarrassed to talk about being fast with a motor on your bike.
2. I tackle hills and mountains on most rides, and increasing top speed by adding voltage means the minimum speeds required to keep you motor and controller safe go up too. I have to slow down for curves going up steep hills already, so going up in voltage would put a lot more stress my system in the form of more heat, lower efficiency, and higher phase currents with very little gain in useful performance.
FWIW, I've settled on a phase/battery current relationship of 13:10 . Lower than that suppresses launch acceleration and top speed, though I don't understand why it affects top speed. Higher than that makes the bike unmanageable, and with my big load with much lower and more forward CG than typical along with a longer wheelbase I still have to work to keep the front wheel down. Sure I give up some thrust from a dead stop, but I don't care about the first 2 or 3 tire revolutions. The last thing I want to do is pull up to the front of traffic at a red light only to get flipped on my back when the light turns green.
John