Hi and thanks for the response. Yeah the bike currently weighs 240 pounds with my lithium pack (24s 8p). I wouldnt be doing the re-winding, I would take it to one of our people here and have them do it. Being that it is a 28 pole motor I am assuming has something to do with why it is so speed limited, but something doesnt make sense as the 72 volt Lead acid versions will do 50 kph, so I thought the increase in voltage would be more than what I am getting. An ebike dealer here thinks there is probably a board or something preventing more speed in the motor??..never heard of that one before!.flippy wrote: ↑Dec 29, 2017 5:49 amtop speed is dictated by voltage, nothing else. you already have the wattage you need for more speed.
you need to modify the existing pack or replace it with a higher voltage.
replacing the motor for one with a higher kv should be a last resort as motors like this are REALLY expensive.
i would not recommend rewinding a motor with zero experience.
might want to upgrade the controller to a 96v model.
Punx0r wrote: ↑Dec 29, 2017 11:46 amHow much more speed would you like?
A motor controller with flux weakening might get you there and let you keep your battery and motor as-is.
Alternatively, is this motor likely to be already configured in delta? If not, reconfiguring from star/wye would give a good increase in speed for the same voltage.
Yes the CA is telling me what the voltage and amps are. Bike is 240 pounds, and 400 pounds with me on it. The controller is a crystalyte 18 fet set for 80 amps but the most I have seen it pull was 70 and mostly 65. The battery is a 24s8p that is getting tired as I am over the max amp draw for this battery (Made it with the Panasonic NCR18650B cells which are only rated for 5.8 amps each. Resistance as measured by the CA is about .165 ohms. Max range at 50 kph was about 38 kmsx.l.r.8 wrote: ↑Dec 29, 2017 3:02 pmSomething sounds wrong, Is the CA verifing your voltage/Amps because I would expect the increase in voltage to be pushing closer to 60km/hr. Its a super heavy bike but so are a lot of DUI scooters and they are going 60km/hr for 50km with pretty much an upgraded controller and good battery reserves all around the 72v mark. I reduced my voltage to 65v and still see 45km/hr for 40km using hoverboard batteries. Sinking 7Kw into a hub should produce much better results.
Thanks for the reply..but "kills efficiency " isnt very helpful..on the Sabvoton controller, it has Flux weakening up to 150 A...but doesnt recommend beyond 50 A as it says it can de-stabilize the magnets..so if I were to say program the controller for 20 A and I get 20 KPH more speed what is the efficiency loss?..does it directly correlate to the amount in percentage of speed gained, or is there a formula??
Its funny ..I forgot that a guy called me and bought the same bike and asked me tomake a pack. I made a 20s 8p pack from Panasonic PF cells and when it was done,had 20% less resistance than my 24s pack and when we went for a ride together, even though I had better accelleration, the difference in top speed was only 5 kph!!...and that is with his stock controller and my crystalyte 18 fet beast.x.l.r.8 wrote: ↑Jan 01, 2018 4:07 pmI’m with the controller to. Your battery is 3 times better than mine and I get easily equal your performance. The motor will do 75 km/h with 72v so any of the proven controllers (Kelly, power velocity, sabvoton) would probably do what you want. All should plug up to your CA. I wouldn’t go charging the motor yet as it easily does what your after.
Thanks for the post...yeah so the article explains why the motor stops accellerating once the back emf eddies build up...so the sabvoton controller counters that which enables more speed...I am thinking that it wouldnt take much to increase speed 20-25 kph...
Yeah I know I am way over the amperage the cells can take but remember I am only drawing 65 amps for a couple of secs then it tapers off...it sags to about 83 volts from 99 volts from a stand still..and to about 87 volts when I am crusing at 30 kph and then apply full throttle...BUT consider this; Just for heck I detached one cell (after 330 cycles) and did a capacity test...that cell had only lost about 6 percent capacity!!...couldnt believe it so did one more and it was the same...almost never take the pack down to empty..ususally charge it back up at about 87 volts..icherouveim wrote: ↑Jan 01, 2018 3:17 pmHello,
There is something else you should consider. My first battery pack I had 3 years ago it was made by 18650B panasonic cells. They were very weak, the battery pack was sagging alot. Just to give you an example when the battery pack was fully charged each cell was sagging at 3.3V!! while I was drawing only 4amps per cell and you draw almost 9! This battery pack is going to die very soon.
So firstly you need a new stronger battery pack and if you still have the same low top speed then you can change controller and or modify-replace your motor.
I understand that, but they are 2 sides of the same coin...at 1 amp those cells came in at 3000 mah..and after 300 cycles at the same amperage discharge, they are around 2850 mah...resistance can be calculated and involves a known resistance and sag under that resistance..well we know the resistance and the capacity, and the sag is about the same (the whole pack through the cycle analyst which calculates this based on voltage/load and voltage sag), so considering I have not been kind to them, this is an excellent result. Doesnt matter to me as I am going to make another pack 24s 16p from Panasonic PF cells as they are the best bang for the buck, and this pack should be able to handle 80-100 amps peak very comfortably.