48V E-biker from OZ

[1WDAussie]

I am an ebike enthusiast from Australia. Am running a 1000w 48v BLDC setup on a DaBomb frame (CYCLONE). Hope to share knowledge with fellow ebikers around the world.

Have had 4 controllers now blow on me. The mosfets seem to continually go. Have sent back and problem seems to be the current set to high on the motor itself. Has been re-adjusted in Taiwan and will be coming back next week.

I fear it may have something to do with my gearing so some help with gear ratios would be fantastic. I have a 8spd nexus internal on the back. Anyone else with CYCLONE setups please contact me with any comments on what they have done.

THanks everyone,

Jon

 

[pylonflyer]

Hi, buy or borrow a clamp on style DC amp meter and check amps when riding. You only need to clamp over one wire in line between the battery and speed control.

 

[1WDAussie]

Thanks for your reply, my controller is 35A, is there an easy way to have some sort of 'cut-off protection' if too many amps is coming thru?

 

[terrence]

Hello 1WD Welcome to MB.c Glad your here. Im not a e-bike guy but someone should be able to help. Start a new thread if you dont get a good responce in your introduction. Enjoy, terrence.

 

[brisbane_boy]

hey mate
good to hav another aussie on here
Where are u from ?
Yer i dont hav a electric but iv heard the 1000w are crazy powerful
WELCOME

 

[1WDAussie]

I'm from Melbs bris boy. Do you guys have to register ya bike if its over a certain c.c??? Would love to have gone a petrol motor but riding on the trains is banned down here with an engine, and you have to register the bike as a motorbike unless its at some piddy c.c.

1000w elec does go well but really chews up the old juice

I realise this is more an intro thread so I'm starting a new thread today for help with things like gear ratios. If anyone can help, please check it out.

 

[duivendyk]

Controllers control the voltage applied to the motor,by varying the on/off ratio of a electronic switch (the MOS Fets.This controls the motor speed but not the current.In principle the controller could also be made to control the max. motor current,protecting the switch.But apparently yours does not.You need a 25/30Amp breaker,most of these use a bi-metal that carries the current, if it gets too hot it trips.So it should work on dc too (hopefully).when the thing trips you lose power but not your Mosfets.A motor can draw a lot of current on hills.Does the motor drive the bike via the hub or independently?.In the first case getting in a lower gear would help in keeping the current down.High voltage and low gearing would keep the current down and the motor rpm up,which is what you want,for max. power and lowest current.But only if you can run through your geared hub.

 

[1WDAussie]

Thanks Dui,

I dont have a hub motor, I'm using an independant brushless motor to a free-wheel crank, then off to my rear 8spd hub. I drop gear when I hear the motor starting to struggle. I have a feeling I am using the wrong sized gear on my back wheel. Would the bigger cog on the back help, or smaller to draw less current. I found my speed is as much as I need so dropping max speed is fine.
Does this breaker your talking about keep working after its tripped? Can you reset them or is it like a fuse where you have to replace it??? I have a 26" wheel and I remember when buying the kit they recommended them to go on a 24" maybe this is my prob???

 

[duivendyk]

Yes gearing lower allways helps.To get mathematical (not too hard) the basic motor equation is: V = IxR+ (back emf).
V is the voltage from the controller,I is the current, R the motor loss (represented by a resistor,mostly copper losses in the windings )and the back emf is the voltage generated by the armature rotating in the magnetic field.This voltage is proportional to the rotational speed of the motor.If the voltage drop IxR is small (an efficient motor).The motor speed is pretty much proportional to V.The motor torque is proportional to the current and the input (and the output) power are proportional to current and input voltage (as I said speed is proportional to voltage.So to keep the current down you have to run it at high voltage (high rpm) and relatively low current,that is with lower torque, but recoup that torque with lower gearing which you can afford to do since it is running at high speed.
The circuit breakers I was talking about are the type commonly used in the US in residence main panels,they are reset by hand and are springloaded,the bi-metal strip when it heats up due to the current trips the switch which has to be reset manually.I was theorizing that since the thing is heat operated it would not care wether there was dc or ac going through it.That is not entirely true,to open dc switch produces more of an arc than an ac switch because the voltage does not go through zero in a few milliseconds as with ac.But it would probably work OK at 48V .I don't know if these type of circuit breakers are used in Australia.Iwould imagine though that they are.In the UK they are very big on fuses, every thing in sight is fused,even power cords

 

[1WDAussie]

Thanks for putting some time in explaining Dui. I asked the seller about your suggestion and he agreed it would help. I recieved an email from 'cyclone' where the motor is being adjusted and controllers fixed, this is what he said (PACO):
"Keep the current under 40A.
45A~75A for less than 10 secs
you can get a 40A~50A dc breaker, or I can get from here cost is about 35USD"

I'll look here in Oz first but I might just pay that in the end. Sounds a little dear though.

The seller also included a smaller chain wheel for my free-wheel crank.
Before 14 tooth driver, then 36T& 44T at freewheel, and 18 at the rear. Now it will be 14 tooth, then 30T &44T, then 18 back wheel. RPM of motor is 3600.

Hopefully this fixes the problem. Get it all back end of next week.
Jon