Arlo1 wrote:Thanks for the links Dave. Its funny becsause one of the charts at the bottom shows 40% for comercial use as the max and I found 40-50% of the irfb4110 ratings is what I can get with my moded chineese controllers. So I have been close to what the chart sugests.
Many people blow up controllers because they run them at their absolute maximum ratings (me included at times). It's something I'm trying to get away from because I know it's a bad practice. Just because you can run your 12 FET IRFB4110 controller at 100V 100A doesn't mean it's the wisest thing to do. It may survive for a while, but a hot day, a voltage spike, a steep hill etc is all it takes to push it past it's breaking point.
My 18 FET controller with 4115s should be able to do 210A per bank of 3 FETs at 100C if it had none of the typical losses and went straight from the datasheet specs, but I know that's not realistic. That's why I've decided through temperature monitoring and experimenting to not exceed 105A battery amps / 130A phase amps and I normally only run it at 85A battery, 115A phase. Before anyone says it, yes I know the FETs only feel phase amps, I'm just listing both settings here since it's what most people are use to seeing on these controllers. With temperature monitoring I make sure I never exceed 80C either and I rarely ever see over 65C at 85A/115A unless climbing a steep hill at low throttle.
Even if my controller was built with IRFP4110 FETs and I kept the voltage around 82V, I still would not go more than about 10% past these settings because the reality is the TO-220 package is what causes the limit with it's small legs and poor thermal transfer characteristics.
It is possible to burst numbers higher than what I'm posting as many people have done, but if you want reliability you should size your controllers more appropriately and monitor them as well. Modding them to improve cooling / thermal transfer doesn't hurt either.
Someone here can correct me if I'm wrong or have observed something different, but I've noticed wheel size plays a big difference in what you can get away with when pushing the limits when using a hub motor. The smaller wheels allow you to accellerate more easily meaning you are demanding power from the controller for a shorter amount of time. Once up to speed and the amps fall off the controller has time to cool off again. You also need less phase amps to get you going.
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