Avanti Electric Bike Motor

Dissapoinment, dissapointment, dissapointment.

I was recently given an avanti ebike motor to have a 'play' with. The avanti is the only motor on the market that I susupected was truly limited to 200watts.
 

The person who gave me the motor was very disappointed in the motor as it did not have enough power to assist him to the degree he needed, so he gave to me to see if I could 'oomph' it up a bit. The idea is to use a different controller on a higher voltage with higher amps to see if it will perform better. I was really hoping the motor was designed as a high performance/high power motor but being used well below its capacity. But alas that appears not to be the case. So improving its performance may be problematic, will see how it goes.

I was really hoping that the avanti electric bike motor would be the same design as the csiro solar car motors, but alas the motor does not use the halbach magnet array and doesn't use litz wire, so it is in fact a very standard type of motor. It is an axial flux type motor which is a common motor structure ( eg fan motors in most cars use them ). So it looks like the efficiency of this motor is not going to be in the high efficiency ranges of the solar car motors. In fact if you look at the graph the company has supplied on its website and extrapolate back to the rpm of an ebike motor ( less than 300rpm ), from that graph the efficiency would be around 50%. I suspect the graph they have supplied on their website is not for the avanti motor but for another one of their motors ( it doesn't show the rpm range of an ebike motor but much higher motors, perhaps the motor they use in ceiling fans has been supplied on website). It also states on that graph that competitors motors are around 65%, in the case of ebikes, over 80% is very common with brushless motors. I think there is verylittle  technical information can be taken from the imtmotors website that relates to this ebike motor.
I was recently given an avanti ebike motor to have a 'play' with. The avanti is the only motor on the market that I know is truly limited to 200watts.
The motor was designed by In-Motion technologies ( a company associated with Northern Territory University, Darwin) (imtmotors.com).

Heres some tech info on the avanti ( imtmotor):

I tested the maximum amps supplied by controller. It reached 16amps. On a fully charged battery ( the motor runs off 12volts ) the power input max. would be P=V*I = 13.2v*16amp= 211.2watts  .  I have no idea what the efficiency of the motor is but lets assume its 90% then the maximum power output would be
211.2v * 0.9= 190.1watts       I think its unlikely the motor would be over 90% efficiency so it looks like it is actually a 200watt limited motor. The only motor I know of in Australia on ebikes that is actually within the legal power limit. ( by the way 200watts is a very very very low power limit for ebikes and in my view not practical at all for useful transport via ebikes. You really need about 900watts plus to be able to tackle decent hills with minimal effort, its just physics! australia is way behind other countries in the power limits for ebikes, in fact the limit is so low that it is acting as a deterent against the introduction of ebikes, with all the publicity about global warming you would think the powers that be might see fit to assist in the introduction of electric bikes rather than deter).

Heres how I opened the motor up:

First I took off the controller, required unsoldering the three thick phase wires, they was an awful lot of solder on there but was simple enough to take off with soldering iron.

Anyway I opened up the motor, quite a challenge to open it up. The allen key type screws are locktited in place, and the allen key hole is very small diameter, so it required quite a bit of technique to undo them without stripping the allen key holes. I managed to get the all out except one which i had to drill the head off. I had to use a very tight fitting allen key, knock it into the keyhole with a hammer, then using some socket set extensions push down with all my weight while turning anticlockwise. Will most likely replace these with hex head screws on re-assembly. Ok so thats problem one, hard to take motor apart, allen key holes under undersized for the job.

Only the six inner screws need to be taken out to dismantle the motor, the outer ring of screws holds the coils/stator onto the aluminium backing plate and have to be kept in place to open the motor completely.

To the get the coils/stator and backing plate to come out of the hub was also quite difficult, it required quite a bit of levering on the sides of the aluminium plate against the out hub casing, the outer hub casing is fortunately very good quality metal as it bent quite a bit during the procedure but didn't break. So sort of puller tool would make the job alot easier.

So once it was apart, very dissapointed to see very thick copper coils ( approx 5mm in diameter ) .......no Litz wire!! The coils look like that could take very high amps, similar to a car starter motor, maybe 100amps or more. They are very thick and a very low number of turns in the copper. Ebike motors that run on higher voltages usually have 6 or more strands of 0.9mm wire wound around a stator, so the likelihood of this motor running well on higher voltages I think are very limited.


The other big dissapoinment was to see just standard north/south magnets, no halbach array! So although this motor is a spin off from solar car motor design it doesn't appear to use the technology of solar car motors.............very suprising indeed. It uses a slotted stator which I have no idea if that is a new design or not, but there have been guys building their own wind generator motors (otherpower.com ) which are quite similar in principal.
You can also see my P3 motor page has the same type of axial flux magnet array used in it (avanti on left, my P3 motor on right below)

Avanti below



The coils also do not represent the structure of the csiro solar car motor very closely at all. So basically what I was hoping would be a csiro solar car type motor is in fact something completely different.........oh well.

anyway will do some experiments with overvolting and over amping the motor and see what happens. I'll replace the onboard controller with one of higher voltage and amp rating, most likely 48v 18amp to start with. If the motor will perform better it will also require some modifications to how the motor sits in the bike dropouts to handle the increase in torque/speed. I'm not sure what voltage the hall sensors run off and whether they are 60 or 120 degree spacing, should have measured that before I took motor apart........whoops.

I should say something positive about the motor: the controller looks quite sophisticated, and the amount of time and effort that has gone into developing this motor must have been huge. But if they had only made a high power/high torque motor like the csiro solar car motor and ran it way below its specs, would have really allowed the bank yard tinkerers to have something special to play with........oh well.

Sorry one more thing on negative side. The outer hub design unfortunately it looks likes the designers didn't know about the chinese made hub motors which have solved the problems of the outer hub design. So the spoke setup is not good at all, seems they have tried a retrofit measure to solve the spoke strength problems by puting some horizontal spoke tensioners in the design, but really would have been much better to just make the hub like common variety hub motors.

A few pics of controller for the boffins.
  

I still think the next motor to emerge from china will be something like the csiro motor, just a shame the avanti is not same as the csiro motor.

beware of spray ebike company: more info