Today i repaird the defect 12F AOT290 controller.
There was a short between battery minus and the green phase (thus the low side Fet's), but the QUESTION is why this happened with only 48V battery and a small 9C DD hub motor?
From what i found out the reason could have been a poor heat transfer, melted insulation washers and a short over the bolts and heatsink.
check out the pics:
There was an aluminum chip near the bolt hole which led eventual to a gap and poorer heat transfer. This was behind the FET which died (on the far right where the green phase wire is soldered).
some of the insulation washers i removed (most of them also from the FET's in this area).
As you can see they probabaly got to hot and melted which led to a short through the bolts.
measuring Rds on with 10V on the Gate:
I purchased the AOT290 from digikey, and they all had about 2,56mOhm (+- a few percent which should be in tolerance).
first one:
second one:
the one i unsoldered from the controller had much higher resistance (but still within specs of <3,5mOhm). Note that it looks differnt:
on the left the one from digikey:
The meter is really accurate. The shunt of that controller is declared to have 2.00mOhm and this meter measured exactly the same.
As summery:
Vadim, or the producer of powervelocitiy controllers should absolutely do better quality control.
Aluminum chips leading to a gap between the heatsinks, messy attachment of the kapton tape, insulation washers which melt and causing a short, and loose BT modules flying around inside....
MAN, maybe i had bad luck or just got "monday" models, but in order to avoid these messy-flaws it would really not need much
regarding the FET's:
It is a fact that there are different batches around from the AOT290.
It makes a huge difference if you have ones with 3,4mOhm or 2,56mOhm in your controller. Latter means 25% less resistive losses or about
15% higher current!