Alan B wrote:Outstanding service from Zombiess! Really above and beyond.
More on Power Levels
I did some analysis of power in the ebikes.ca simulator. Justin has hubmotor dissipation set up for 500 watts. Let's assume for a moment that is correct. If you put in 4,500 watts and the motor can only dissipate 500 watts the efficiency must be at least 89%. The values I see are more like 87% max on the simulator, which corresponds very nearly to 4,000 watts input and 500 watts dissipated. So if these numbers are accurate, putting 4,000 watts into the motor puts it right near maximum dissipation. So I would interpret when they say 4,000 watts maximum, that it is under ideal conditions. It is not safe unless those conditions are met. Anytime you exceed that it better be for a very short time, and really you should be monitoring winding temperatures.
Efficiency drops with RPM as we know. From the simulator, 87% was at 500 rpm with 150kg mountain bike on 24" tires. I got 73% at 100 rpm with the same setup. These correspond to about 35 mph and 7 mph. So this means we can handle 4000 watts at 35 mph and only 1900 watts at 7 mph. At zero speed the maximum power is 500 watts, so it rises from there to 2kw at about 10 mph. Of course with a 29'er these numbers are all reduced a bunch. They are also steady-state, accelerating will lower efficiency quite a bit, so you can't do it too often or the heat will build up. Indeed, if you accelerate then cruise, you really should not cruise at 4000 watts since you need to allow some margin for recovery from the earlier acceleration.
To summarize, perhaps the 3000 watt value printed on the motor is a really good value to use for continuous running at good speed. Use the 4kw feature for "turbo speed" mode, and exceed 4kw only briefly as a "risky event". Derate it to 1500 watts at 10 mph and 400 watts at zero speed. Exceed these values only short-term.
Alan, you can't use the version in Justin's simulator, it's not close to reality until he updates it with the data I sent him. It's WAY to optimistic on efficiency, it says that at WOT on my bike I'd only draw 50A at 55mph on a mountain bike when the reality is in a full tuck I'm drawing about 60-65A at 57MPH at 100% throttle and that goes to about 75A if I sit up. Use the simulator links I posted in the 1st post of this thread if you want to simulate this motor, it's almost identical to what I get on my bike.
I just sent him a PM asking if he would update his simulator with the data points I sent that he asked me for.