Force GT BPM build

Objective – Build an all mountain/trail E Bike

Criteria
Bike must be light, well balanced, have good suspension and handling, and plenty of torque.

Components.
1 x used Force GT (large)
1 x BPM geared motor with hall sensors (code 12)
1 x 24” rim
1 x Lyen Infineon 6 fet sensored controller
1 x Cycle Analyst V3 Beta
3 x 8AH 22.2v Lipo batteries (18s)

Outcome 8)
Weight – 24.00kg
Top speed - 53 kph
Range – 30 km (no pedalling , speeds 30 – 45 kph)
The bike has plenty of torque, on gradients it will wheel stand if you turn the throttle to fast. It gets up to speed very quickly, and is great off road.

Power Issue
When I first set it up, The controller was limited at 50A in error, because the shunt was modified. It was very twitchy to ride, wheel standing with the slightest touch of the throttle. I had the CA limited to 25A, but it still had the full 50A for the first second of throttle change. Once I corrected the settings in the controller, it now peaks at 34A and is great to ride.

I plan to paint the battery and controller box white.

Here are the build photos.

















Questions and comments welcome
Cruzxia

Nice work cruzxia. That bike lends itself well to the underslung battery box. Have you mounted the controller internally? I can imagine this bike would ride really well with this setup.

Yes the controller is mounted internally. I used the controllers original box, and added a 3mm right angle heat sync on the outside of the box, which is then bolted to the inside of the battery box, on the wind side of the casing.

I added a thermo couple to the controller, that is glued against the main fet mount alloy block.
The highest temperature I have seen is 57 Celsius. Because of the large heat sync area it is very slow to climb in temperature.
When I next dismantle the casing I will take some photos.

My original plan was to buy a Giant with the rear shock mounted out of the way and mount the batteries within the triangle. The Force GT came up for sale locally, and I couldn’t pass it up, so I revised plans. It is a great feeling package, the ride is very well balanced, and has plenty of acceleration.

I like the battery box too. Must be good for a low center of gravity,and looks quite bash-proof...

That is pretty much exactly what I would build for an urban assault vehicle.

Very nicely done.

Few updates on the bike.
I have revised the gearing now, It has a 46 tooth chain ring and the rear is 11-30 tooth. With the 24" wheel you can happily pedal along at 45kph, and in low it will go about 15kph, so I am very happy with the spread.

In terms of range, it is very efficient, I can easily manage 37-45 km with a bit of pedalling and traveling at speeds of around 35 kph
The batteries are 8ah but the usable capacity is 6.5ah, and the LVC is at 61v.

The battery box is made from 1.5mm alloy and is very strong. I still have not painted it, but it is on the to do list.

Looks excellent. I was building the same bike but had problems with the components on my bike so I went with a different one.

Enjoy the ride!

Tom

hows the bpm holding up at 18s? I have a 12 mile commute, and seems like high voltage is the way to go with a torquey wind.

Whats the top end of it? I was going to use a 26" wheel however.

The BPM is holding out well, I run 1800w on the CA, and it peaks on acceliration at around 2300w. I am using a sensored code 12, I opened it and it still looks like new inside. I have covered about 350km so far. Top speed is 53kmh, due to the wheel size and motor winde. In a 26" you will probibly pull 60, but it will increase the load on the motor.
The torque is great, it will hold 45 up hills.

Cruzxia

so if i was at the site, would i order the 48v kit in the 201 wind?

ill be running 18s aswell in a 26" wheel, so very torqey and 40 mph is perfecfttt

I would get a code 12 so if you order from BMSBATTERY order the 48v 328rpm motor, it should be a BPMII code 12. (No guarantee) But I ordered one about 4 weeks ago and it was a code 12

Here is a spread sheet with your wheel size (aprox) it will show you the difference between motors and speed.



If you let me know the wheel size I can re post the chart.