mistercrash wrote:I read in here that someone had great success in bringing his hub motor temp way down just by sealing the end caps, drilling a small hole in one of the end caps near the axle and putting ATF inside the motor. I am thinking of doing the same thing to help cool down the motor better than just with air. This might help run this motor even with 72V.
There is some validity to this practice but it has a flaw. It is the viscous friction of the fluid. This friction wastes power used to turn the motor against the fluid. This is why automatic transmissions get hot. The cooling medium actually consumes large amounts of power power as it warms. During operation it mixes with air which reduces its cooling transfer ability. It heats up a little more. When it reaches the outer hub it transfers this heat which is seen as a higher temp than was seem with no coolant, however it is not a direct indication of how well the coolant is reducing the internal temperature. To know this you require an internal temp probe situated in the windings.
In our case (small diameter wheel) the motor turns at a much higher RPM than those in a bicycle running at the same road speed. Since our motors are, for the most part, larger in diameter than bicycle hubs the rim speed of the motor is also higher per RPM. This increases the sheer action working against the fluid and theoretically adds more heat per equivalent RPM. For the fluid to work its best theoretically the system should be 100% full. This adds more weight to the vehicle which requires more power to move it. It also increases the total sheer. A full hub would also consume more power as it warms up. Eventually it would stabilize somewhat but how long that would take is anyones guess.
Another factor that comes into play here is that one does not know what the actual temperature of the fluid is. If it goes over a certain temperature and mixes with oxygen its properties start changing. This may lead to erosion of the winding insulation.
Just trying to point out here that there is more happening inside the motor than one knows. I am not trying to start an argument. If it appears so, I apologize.
mistercrash wrote: I don't know about any shunt for my CA as I have the direct plug in model. The speed limit option of the CA, I read a bit about it in the instruction book but I'm not sure exactly how it works. I suspect that you have to access the setting and then change the values to reduce the speed and set it. I don't see how this can help when you want to quickly reduce your top speed on the fly. With the thumb switch, I flick it and it's done, the top speed is reduced to whatever I set it to in the controller. With the CA, from what I understand about it, I have to start pushing buttons many times to reset the top speed. If I figured this out correctly, it's not very convenient to do while riding.
Oooops, my bad on not noting the plugin version. As to the speed control, one would simply install a SPST switch in the wire that connects the CA to your throttle. You would program in the speed you want and play the switching limits (hysteresis) to smooth things out. With the switch in the one position the throttle signal is pulled down when the set speed is attained independent of where you are holding the throttle. Turn the switch off and the CA cannot draw the signal down, you have max speed. No need to constantly push buttons. As Ron Popeel on TV would say, "set it and forget it".
When the the CA speed limit is turned on it only limits the speed by throttling back the power at the configured speed. It allows full pack amperage to be used at anything under the limit allowing max torque for the hills. The speed switch limits the power across the board by limiting amperage. Another nice thing about using the CA speed setting is that you could adapt a multi position switch to allow limiting at different speed by using dropping resistors in the circuitry.
One thing just occurred to me.
Since you have the plug in CA does the CA speedo signal interface with the controller or does the controller use speed sense via the hall switches inside the motor? If it uses hall signal and a SW configured tire diameter to calculate road speed then it could well be doing the same function. If this is so then the CA is redundant for this function and I have been rambling on.
mistercrash wrote:The CA shows me that when riding I consistently use around 38 Wh/Km. I always am at WOT. So I figured I could have a range of 55 km with a 72V 30Ah battery.
Geez, I just came back from a 38k ride and ran only 20wh/km. My take here is that because of the make up of the internals of your motor you are having to use higher voltage to try and push more amperage through the windings for more power. The problem here is that the power is being converted to heat rather than torque to move the vehicle. To get a certain level of power with a given wire size you have to have a certain number of turns. The more turns the more magnetic field developed with X amount of current. The problem here is higher winding count introduces a higher back EMF as speed rises. All this stuff fights itself and many just keep upping the voltage trying to pump more current through. This just just raises temperatures. Without thermal protection for the motor a big controller can kill the motor because it has no idea what that temperature is. In a future upgrade I am going to tap into my thermal sensor inside the motor and mount a display to show temps. Another thing I am going to do is glass bead the motor housing and paint it flat black. Flat black can have up to 10 times the radiating affect as a white or polished surface. When you see anything used in racing that generates heat, it is never polished, chromed or painted white.
In regards to the battery pack, I too was stating my reasons for going the TS route not to argue the point. Again I apologize if I gave that impression. Yes my pack comes in at just under $1k and I ruined a few cells by going with the mainstream thinking. So my investment in cells alone comes in at the price of the scooter.
I don't need to tell you what a difference it makes to loose 70 pounds on these scooters.
Just telling you what the reasons are for what I did on my scooter. I would love the have 72V and 40Ah of those Winston cells, they just seem to be the best option for the large differences in temperatures we get up here in Canada, but I would need to build a bigger battery box to house them in my XPn. And they are expensive.
I did a 38K run last night. Went into the area the Arlo1 has his shop. 3 times I got tailed by the boys but never did get pulled over. Just did the limit on level ground and followed the rest of the rules. For the most part they look for a tailpipe and if it makes put-put sounds when it sits a stops.
Except for the locked pedals.
