Amps seem to dwindle off WOT, 18fet programmed wrong? (pics)

markw

10 W
Joined
Jun 9, 2014
Messages
90
Location
Portland, Maine
Hi there,

Testing my controller settings on my heavy vector bike / mxus 4t / 20s 25Ah LiPo battery. Programmed settings on my trace upgraded 18fet were at 64 battery amps / phase limits at 165. Predictably, my max battery amps real world were at ~82 peak... but by no means did they sustain that current output - it peaked at 82a but by no means sustained that output at all. I was disappointed to find that WOT on a 0% grade that I was only pushing ~40amps/40~mph.

I'm wondering if this is a programming shortfall? Perhaps my phase current limit is set too low to sustain high current output at WOT? Maybe it's something else, what do you guys think? Thanks in advance for your advise :)

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It is normal for current to fall off at WOT as the motor speed maxes out due to the voltage ceiling. Instead of accelerating, you are only holding a constant speed which takes much less energy to do. Same as in a car, it takes way more gas to accelerate to freeway speed than to hold a steady freeway speed. Try WOT uphill and the current should stay high. I think this is what you are describing at least. If so it is normal controller behavior.
 
If you are not slowing down once you reach top speed, then it is normal falling off of current as load decreases at top speed. You see, there is no more accelerating that needs to be done, only maintaining the speed you just accelerated to.
Holding the tire off the ground will not reveal any useful data, as no load and full load speeds vary per installation because of all the variables including tire pressure, weight, drag profile etc. That is misleading instruction, in my opinion. I run a 4t at 72v 5500w peak.
 
it's not misleading. a bike reasonably built and configured should be able to reach near no load speed at full speed and WOT. if not it's imho not geared correctly, too weak, too heavy, too whatever. and seeing no load speed gives you at least a number you know which can not be exceeded. so if no load speed is 50mph you can not expect the bike to go 55mph, and not 50mph. probably not even 45mph. you get the idea.
 
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