Help me understand my new ebike

[MomentumUpstart]

Hi, I bought one of these ebikes, its an australian bike so you wont know it but it has a Samsung battery and a Bafang 500W rear hub motor.
http://www.reefbikes.com.au/products/Predator-Offroad-Electric-Bike.html

It is speed restricted to 35km/h and I want to remove it. I havent managed how to get access to the controller yet. What I can see is that there is one large gauge wire going to the axle of the rear hub motor and a small gauge wire going into the crank area. Is the crank area wire the speed sensor? I have attached pictures of both wires. The rest of the wires go up front to the lcd display, brakes, throttle and buttons. Therefore I think it is one of these 2 wires that is used for the speed restriction.

 

[trex]

try holding both + and - buttons down for 5 seconds to get to the settings.

 

[Deleted member 4366]

I doubt very much that it's restricted. 35km/h is the motor speed. The only way to make the motor go faster would be to replace the battery and controller with higher voltage ones, say 48v. Alternatively, you could replace the motor with a higher speed one. A code 10 BPM will get you up to about 40km/h at the expense of low-speed efficiency and torque. Torque would be higher at speeds over 30km/h because of the higher RPM limit.

 

[Nealh]

35kmh is a high cut off speed so yours isn't restricted, if it was it would be set to 25kmh. As Trex has said you will need to look in the lcd settings for any adjustment.
Wiring wise rear hub set will be motor phase and hall sensor if used and the small crank area one will probably be the rearwheel speed sensor or pas.

 

[Deleted member 4366]

The wire to the crank is for the torque sensor.

 

[MomentumUpstart]

So I pulled the controller out and cant see a brand or model number.

Then I saw the post to press + and - to go into settings. So I put everything back together and yup there is a max speed setting, I bumped it up to max which is 40km/h. That will keep me satisfied for a while at least.

Thanks trex!!

Its a specific "high power" "offroad only" "not legal bike". Riding with the wind I was hitting the 35km/h max throttle only! So its definitely not the motor maxing out at 35km/h. Will give it a good test tomorrow and report back.

 

[Deleted member 4366]

You can change the speed limit, but the motor might still max out before it reaches 40km/h. Please let us know how fast it goes now.

 

[MomentumUpstart]

I had a stretch of path last night that it was sitting on 37km/h with full motor assistance. I couldnt physically get the bike going any faster with the wide knobby tyres and a bit of a headwind. Hopefully I have better conditions soon to see if will keep providing assistance up the to the 40km/h max.

Its a Bafang 500W rear hub motor with a 36V Samsung battery. Looking at the site below it looks like 36V means higher max rpm but less torque getting there.
http://www.elifebike.com/peng/iview.asp?KeyID=dtpic-2012-5S-Q4CQ.2MJWP

I have ordered some nice thin 100psi slick tyres to go on too

 

[Deleted member 4366]

We know the speed of 500w Bafang rear motors. They have the speed code marked on them. It will have a number like 36v500w 26 (11), where 11 is the speed code. What are the markings on yours?

 

[MomentumUpstart]

Dammit, I forgot to check the speed code this morning. Did some more testing while cycling in and yeah anything above 35km/h is a lot harder work. I think the max rpm of the motor must be getting reached.

So if I change to smaller and thinner tyres, this will only make it worse correct? The diameter of the tyre will decrease so the max rpm of the motor will be reached at a lower speed! Thats not good

 

[Deleted member 4366]

With thinjer tyres, it's easier to hold on to your maximum speed, so, even if your top asdistance speed is 1 mph less, you'll have a higher cruising speed.

 

[MomentumUpstart]

Good point, do you think it would be only 1mph though? The bike came with 2.6" tyres, I have 2.1" now and I bought 1 1/8" tyres. So a huge difference

 

[trex]

at 15mph, air resistance counts for about 90% of the bike's power consumption, 10% to rolling resistance. The air resistance is proportional to the power 3 (cube) of the speed. Changing the tyres to thinner slick jets will add a very small amount to your average speed while reducing your safety.

 

[MomentumUpstart]

Speed code is 10

 

[Deleted member 4366]

As I said before, a code 10 will reach about 40km/h on the road in favourable conditions. You need about 20 amps at 36v for that, but the current will probably be below that from about 35 km/h because of the back EMF from the motor.

 

[MomentumUpstart]

That news about code 10 made me happy in the pants!!!

Anyway I can reduce the "back EMF from the motor"? Or bump up the amps?

 

[selrahc1992]

That news about code 10 made me happy in the pants!!!

Anyway I can reduce the "back EMF from the motor"? Or bump up the amps?

FWIW I have a code 10 in a very skinny 700c wheel (700 by 23) with almost the same diameter as a mountain bike tyre 26 wheel - the no load speed derestricted is 24 mph, on the level I get 22/23 mph or maybe 24/25 when conditions very favourable. On my bike anything faster becomes demanding and risky.

 

[MomentumUpstart]

at 15mph, air resistance counts for about 90% of the bike's power consumption, 10% to rolling resistance. The air resistance is proportional to the power 3 (cube) of the speed. Changing the tyres to thinner slick jets will add a very small amount to your average speed while reducing your safety.

Reducing safety with thinner smooth tyres on smooth ashpalt compared to knobby mt bike tyres?? I may be new to ebikes but im not new to bicycles.

 

[trex]

skidding on hills and emergency brakes.
people ride e-bikes at considerably higher speed than with normal bikes, even with good brakes, you still need the large contact area between tyre rubber and road surface to brake.
I think 1.75" tyres are a minimum.
Personally, I believe that hub motors reduce the braking efficiency in comparison to crank drives.

 

[selrahc1992]

skidding on hills and emergency brakes.
people ride e-bikes at considerably higher speed than with normal bikes, even with good brakes, you still need the large contact area between tyre rubber and road surface to brake.
I think 1.75" tyres are a minimum.
Personally, I believe that hub motors reduce the braking efficiency in comparison to crank drives.

yerrss...that would explain all those fat knobbly tyres on tour de France bikes. I have a city bike with fat marathon plus' - I've come off several times at relatively low speed, I have a high speed racer I regularly commute at 22 to 24 mph on on very skinny 700c 23 duranos, never any risk of skidding. I'd like to have some what you're smoking.