Thanks for the advice Zombiess, I've considered upgrading to the 24fet controller... but I think i'm going to put on some more KM's before I pull the trigger on that one. Unless someone wants to buy a discounted 18-FET controller
In the video, I was pulling 125A... my controller wasn't warmer then 55c. Is it still possible to damage the FET's with out overheating it first? I think I'll bring it back down to 95Amps
What would the max discharge for my 20c batteries be? I'm afraid they might be the next weakest link in my build. 30S 2P....
I dreamed of ebikes last night... I can't wait to commute on this bad boy.
Was that 125A your constant battery current or just a peak? What are your phase amps set for? I can tell you from experience that if your case was 55C the internal temps were most likely over 100C and the FETs themselves were probably over 120C! That experience is the fact that I have temperature probes on my FETs and also monitoring the internal case temp.
Just remember that my controller is modded almost to the max with better electrical insulators that have better thermal transfer and also I feed and pull power from the tabs of the FETs using copper buss bars which also double as heat sinks. The only mod I have left to do to it is add some copper to the ground traces to see if it helps cool things down and maybe some cooling holes and a small fan. If you want to see what I did to my controller I have lots of pictures located here:
EB318 controller modshttp://dynamic.opticalanarchy.com:8080/zombie/bike/eb318mod/
And my current project, an EB236 36 FET IRFB4115 controllerhttp://dynamic.opticalanarchy.com:8080/zombie/bike/eb236mod/
Here is a brief rundown of what I've seen temp wise:
At 105A battery 125A phase I the FET's would stay in the 55-65C range and the internal case temp would be about 65C. The case itself was around 33C. This is all with the ambient temp around 15C. As soon as I stopped applying power the temps would drop quickly, FET temps would drop from 60 to 45C in about 1 min and the case temp from 60C to 50C in about 3 mins. My controller is exposed to the open air but has no ventilation. What you really need to worry about is how hot the internal temp of the case is getting to since there is no ventilation, that means the capacitors will be stressed from heat and their life will shorten. Also, running FETs over 80C will shorten their life span, continuous use over 100C the life span drops even faster.
I must admit, I'm surprised that it lived, maybe I'm under estimating what these are IRFB4115 18 FET controllers are truly capable of, but I can tell you, I hate blowing up good stuff because I got greedy. I've done it many times from ebike controllers (luckily just 1) to boosted car engines (a few). Once it gets warmer I doubt the controller will survive very long.
If I were you, I'd consider ventilating the controller at minimum, but I guarantee you are in the danger zone. If you climb a hill at part throttle on those settings you'll almost certainly kill it. To give you an idea how little the case temp tells you watch this video of my climbing some stupid steep hill. At the part where I stopped my FET temps were 88C and that was about 100ft before I stopped so I probably hit 90C!, the internal case temp was in the 60C range and out outside case temp was barely warm, probably 25-30C at most. That 88C temp on the FETs is what made me decide to stop. 40% throttle at 125V climbing a super steep hill creates a ton of heat fast.
If you want to continue and push it, please post regular updates about the controllers survival. I'm very curious to how far one of these can go but have been un willing to test one to destruction myself, then again at 125A phase, 105A battery my bike can power wheelie at 30mph if you aren't fully leaned over the bars so it's pretty sketchy to ride. I strongly suggest turning the block time down to 0.1S (you'll need hex edited software) and keeping the phase amps on the low side.
Your setup sure does look like it kicks serious ass, I just want to see it keep kicking ass.
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