Much More Powerful Pie Now!!!

[o00scorpion00o]

Actually I have a ping battery. I don't think the GM battery would have been able to supply some of the amps I've got from this Pie! 
@27 miles full throttle, I have not ran out of juice yet! 

I like the GM batteries switch and the fact you can mount it neatly on the rack, and the fact it's secure. But I really wanted a 20 amp.


Leslie, if I buy a 1kw kit, I expect a 1kw kit, if It was advertised as 750w then I might not have bought it in the first place. It's not good company policy to falsely sell a 1kw kit, just because most people might not hook up a cycle analyst and not notice the difference, doesn't make it right! And the same applies to the magic controller! They should advertise the kits as they are!


Ok I have made my point, enough said.

I am dying to take the bike to a near by mountain at just over 2650 feet, the last few km's are around 16% and would be a great test for the motor. It's about 22 miles away and too far to go there and back on the bike, I have no way to transport the bike, not in my car anyway! 

[Leslie]

Actually I have a ping battery. I don't think the GM battery would have been able to supply some of the amps I've got from this Pie! 
@27 miles full throttle, I have not ran out of juice yet! 

I like the GM batteries switch and the fact you can mount it neatly on the rack, and the fact it's secure. But I really wanted a 20 amp.


Leslie, if I buy a 1kw kit, I expect a 1kw kit, if It was advertised as 750w then I might not have bought it in the first place. It's not good company policy to falsely sell a 1kw kit, just because most people might not hook up a cycle analyst and not notice the difference, doesn't make it right! And the same applies to the magic controller! They should advertise the kits as they are!


Ok I have made my point, enough said.

I am dying to take the bike to a near by mountain at just over 2650 feet, the last few km's are around 16% and would be a great test for the motor. It's about 22 miles away and too far to go there and back on the bike, I have no way to transport the bike, not in my car anyway! 

But the battery is 50 volts right.  Thats usually what the starting voltage is.

And you said the new controller was doing 20 amps up a hill right?.

If you multiply the volts by the current you get the watts, 50v*20A =1000 watts.

Any way I said I was going to my own DC to DC converter switcher for this relay.

Still not as cheap as a single regulator and relay needed for the higher voltages.  I need the step downs as I want this to make my controller compatible from 24v to 90v hot.  I could get this controller doing 100v if I am carefull.  But another day maybe.

The controller I plan to hook this up to has its fet driver and logic own regulator and resistors set for 48v with no LVC. but has an another power bus that can power it.  I plan on using the switcher to feed all things 12v and below.  Including my light system.  So I will try getting the lm338 to limit to 50v and the switcher to do the rest down to 12v.

[o00scorpion00o]

Actually leslie the magic controller is supposed to be 30 amps. My battery is 52 volts x 30 amps = 1560 Watts.

I see your point in Gm trying to keep to the ratings of their 1kw motors, but they sell the magic controller with their 250, 350, 750 watt motors so, I don't believe that the 20 amp limit is imposed by Gm  to keep within the ratings of the motors, I think the limit is more in keeping with the temperature limits of the controller! The reason I think that might be the case is the fact that they sell a so called controller box with absolutely no ventilation and I bet the controllers were roasting.

Anyway, update time. I have lost cruise control, Wiring is fine and checked with a different cruise switch of the same type. Regen braking is much reduced and I believe this to be because the current is reduced by the software. No big deal. But I did like cruise!

I'm going to use this controller as it is as I want the power and it's working fine now with the mod, I will save up for a controller from ebikes.ca, I don't know if I'm allowed to post their site? I think I prefer the case style as they are easier to mount.

BTW leslie, would it not be easier to use lights with internal batteries? I don't ride far by night, as I would get killed with the standard of some of the roads here+ the crazy drivers! 

[o00scorpion00o]

Okay cruise works again, I guess the magic controller heard that I was talking bad about it! 

I went for a good long spin today and it's working good. It eats hills, I had great fun indeed.  The controller got really hot, but that's mainly because I was pulling 35 amps and going slow up those really steep bits in the woods, and it wasn't getting great air flow. I had not been up anything that steep before with the pie and had to peddle from stop on the steepest parts, but at least I know it will take me up the steepest of hills that is possible to go up on a bike! My old 1000w motor  completely stopped on most of the hills with lots of peddling, I had it limited to 20 amps though, max, It would have fried at 35 amps. It used to get hot enough, where as the pie stays luke warm no matter what!

[Leslie]

The Magic controller fets at 35 amps are producing 21 watts over each channel.

Each fet has a v drop of .6v an at 35 amps this equates to 21 watts inside the fet.

So we make it easy to understand I will show you a picture.

this is your thermal limit, you may need to test the temperature of the fet to make sure you don't execeed the temperature I have plotted.




Some more complex math I need to do with derating so I can tell you your limit current at your packs voltage.



The voltage drop can increase .8v with higher voltages and decrease to .5 at lower voltages so at 24v this can do 50 amps and still only make 25 watts inside the fet.


Some additional cooling may be required to elevate your performance at your set limits and if the above thermal limits are exceeded your controller will die.

[Leslie]

The temperature of the inside of the controller effects the derating.

So your fet may well be operating in normal parameters at first but as the temperature rises inside the controller so to does the fet.


This makes sense to why a fet can do 100 amps but your controller is limited to 50 amps.  Why cant the controller do 120 amps.

If you could keep the controller fets temperature down below 25 deg^oC then it could do 100 amps.  But this is not practical.

A good easy test is to put your nose in after a hard ride and if it doesnt smell right you maybe too late.

For now I suggest on warm days take your controller max amps down on warmer days until we learn more about what we are doing.

[Leslie]

V/I=R

48v/ your 35amps lets say about 25 continuous= 1.4 ohms cold and 1.92 ohms normalized resistance total.  I am not being generous as you should consider a little overhead.



Let assume the pack is as low as .08ohms The motor is .08 equals .16 could be higher and another reason to not be generous.

The fets on resistance is close enough to 1.24 colder and 1.76 ohms hot.



This tells me on this new graph your fets are doing 50^oc cold and getting close to about 125^oc hot at the junction in the controller box .

Yes facing the same load, 35A from your controller shows the fets are cooler than at 25 amps.    When you see the current say 10 amps on a hill this means your fets are getting hot. But of cause 35 amps will get your there. 



With out definitive details about your battery resistances and true current ratings at a voltage on load and what voltages are average after the shunt I can only guesstimate..


Now we look at the forward diode characteristics.

At 25 amps continuous by the looks may be above the 55^oc as the 175^oc is suggesting the diodes reaction to thermal runaway so for the picture and save me a heap of math we assume that the voltage drop on the fet diode is about .9v this equates to

25 amps * .9v = 22.5 watts on the fet.  At 35 amps its 31 watts.



If you look at this graph you have  25^o to nothing head room in your controller.  If you are ridding on cold days now you will be fine.

Where you live I believe it is going into winter but still maybe warmer.  If you lived where I do, Australia northernish, in summer your controller would prolly be toast.

[o00scorpion00o]

HI Leslie,

Send some Australian sunshine here please  It's wet today so I won't be out. 

The weather here in Ireland in summer will rarely go beyond 25-27 Celsius peak, Average is between 16-22 degrees Celsius, It's a very humid damp climate, with little sunshine. The weather is pretty much  dominated by the Atlantic ocean. And in winter usually keeps us mild, Though that seems to be getting colder now, last winter was the coldest in over 50 years!

Okay enough with the weather lol. I have thought of installing some kind of temperature activated fan? or I could eliminate the small controller case and mount the fet's on some decent kind of heatsink. I could cut a hole in my battery box and fix the heatsink to it. I may as well use the battery box as I have lots of space. I could also make it water tight no problem!

[Leslie]

LOL.

Ahh you reading all that techno bable.


To make life easier, On a fresh charged pack, when you go up your big hill do you notice a drop in current as you travel up it?  You may notice towards the end?

Edit:

Oh and you must look at the amps on the steep grade not speeding up out of it.

[o00scorpion00o]

LOL.

Ahh you reading all that techno bable.


To make life easier, On a fresh charged pack, when you go up your big hill do you notice a drop in current as you travel up it?  You may notice towards the end?

Of course I read it Leslie, lol. Not sure I understand it all though!   

I don't notice any loss of current at all under any conditions, however as I said before as the pie builds up speed the current draw reduces, and the controller can cool down as speed increases and current reduces. It doesn't take long even on steep hills to pick up speed. Now in the woods yesterday they were incredibly steep but short, and I could not go at full speed up to them. I usually was going really slow coming up to them as the wood trails are not safe for speed. If I was pulling a trailer with lots of weight, I would definitely use another cooling method or another controller, or riding up very steep mountains for lots of Km's at slow speed. I find it's better to keep the speed up at full throttle as it will use less current once going 12+ mph than going slower if that makes sense?

OH one thing I forgot to say, has anyone with a Magic Pie motor noticed the spokes make noise? It's surely not stealth that's for sure, but something that doesn't bother me as I have so much fun with this motor! It may bother some people as it might make people think there is something wrong!

[Leslie]

 I have to go now so I will answer the question both ways.

If you notice the amps drop as you are traveling up the hill then there is need for concern.

If the amps stay rock solid all the way up your magic controller is thumping the hills.

As you see that the resistance of the fet increases with high temps and this through a single fet will limit your current.

But if the current dips by even a few amps or more amps either add cooling or decrease your amps by half the dip in current.

So if you see 10 amps drop due to the heat, reduce your amps by 5 amps.

If you use cooling, eg heat sinks or air flow etc. Cool it so heat is not effecting you current draw.

Understanding me here?

[Leslie]

LOL.

Ahh you reading all that techno bable.


To make life easier, On a fresh charged pack, when you go up your big hill do you notice a drop in current as you travel up it?  You may notice towards the end?

I don't notice any loss of current at all under any conditions,

 

Well that solves that.  Other than a bad smell you may notice before you boil the controller and hot days you should be well in the clear.

Other controller sometimes have 12 to 18 fets and these will not limit current under high temperatures and melt the motor, where as the Magic controller has some concern with derating.

Efficiency wise it wont matter much having less fets as the watts wasted is the same when current is divided over the parallel fets.

They all drop voltage and this is the diode effect not real resistance like a resistor.

12 fets 18 fets blah blah as long as you keep the heat down off the fets efficiency is adequate.

[Leslie]

This is what I plan to do.

I want to make my HBS hub accept 90v.

I have some winding wire and enough to rewind a spare melted stator I have stripped bare.  I have failed to rewind it the first time due to the fact after very heavy loading I melted the insulator around the stator.

This is what happens when you truly overload a hub until its smokin.

A before and after shot.



I had to remove the stator insulator to rewind and this makes it hard to rewind and get the former paper to stop the stator from cutting into the wires.

I want to design a box with a large heat sink attracted to the controller from the outside into the inside.

[o00scorpion00o]

Leslie, I think you are crazier than I LOL. why don't you just go and buy a pie? 90 volts? why don't you convert an old motorbike? I would be too scared to go so fast. That would give you over 40 mph? Is that not too much stress for a motor like that?


I think it might be easier for me to install a large heatsink on my battery box. Just remove the board from the case and mount the board to the heatsink and put some kind of cover over it.

By the way leslie, how did you manage to cook that motor? 


I would be very interested to know how much power the pie could take. It never gets hot, only slightly warm.

[Leslie]

Leslie, I think you are crazier than I LOL. why don't you just go and buy a pie? 90 volts? why don't you convert an old motorbike? I would be too scared to go so fast. That would give you over 40 mph? Is that not too much stress for a motor like that?


I think it might be easier for me to install a large heatsink on my battery box. Just remove the board from the case and mount the board to the heatsink and put some kind of cover over it.

By the way leslie, how did you manage to cook that motor?  


I would be very interested to know how much power the pie could take. It never gets hot, only slightly warm.

Well if you reduce the current to the motor the winding can induce torque from the voltage, the coils are an inductor by nature.  I will never get the 20 amps of torque at that voltage but if I was to rewind the dead motor with a longer wire with more turns over each former (coil core) I will get plenty of torque and it may slow the motor down a bit.  I wont get much more than 1400 watts out of it.

So 1400W/90v = 15 amps.  15 amps is what I will limit it to via a shunt. With more winding and less current, the motor will be slower than a normal HBS hub at 90v but I may get 65+kph out of her on the flats.  And a lighter lithium pack will take a lot of the load off the motor.  THE AH will be better and more efficient.

Its like a low RPM high torque 220v motor.  It has longer thinner windings and winds out the voltage and converts it to Magnetic density and not so much magnetic intensity.

Magnetic density = amps = torque

Magnetic intensity = volts = speed.

These two can be interchangeable by way of how you wind the coils..

How the motor gots melted.

So!

Who killed the electric bike.

The Wife.  

My wife loves to shop.    





And note the 28kgs of SLA's strapped to the frame.

This was a 36v 750 watt HBS running at 48v 1000 watts.

The motor survived the above abuse OK, it was the next weeks or the week after shop that killed the electric bike.  LOL I would of done the same as we thought there was nothing going to stop this baby.

Poo it stunk and I had to hose it down it was so freaking hot.

It ran for a few days and the hall sensor blew out, so when I repaired I saw the melting and thought it wise to not use this motor anymore and try to rewind it.

honestly I would not attempt to push more current through the Pie.  You may find the current will pick up when you put more volts in and you may gain a little more torque but then again I do think you should enjoy your bike as it is and do stuff when a repair is needed..

This way if you mod when your bike is defunct you are not risking a working bike to try out for more performance.