25mph new build.

erian · Oct 5, 2018

Hi to all.

I have a frame, a steel Surly LHT that i would like to turn into an electric build. I am looking for a hub motor that can achieve 35-40 km/h.

I have only one limitation, I would like it to be 36V. The reason is that I have 2 36V batteries (12 and 15AH with panasonic 18650PF cells) and I am able to switch from bike to bike, I would not want to get rid of perfectly good expensive batteries.

Do you have any 700C kit in mind? I do not really care about torque, more about speed, my whereabouts are pretty flat. I have only one 3% inclination on my 22miles route.

So far I have thought of using a Bafang BPM2 36V500W motor. It should be able to get me up to 35kmh.

Any other even faster *if possible suggestions?

motomech · Oct 5, 2018

Just because you will be using a 36 V pack, does not mean you necessarily have to use a 36 V motor. The 36V/500 is just the factory rating, a reference. A basic "rule of thumb" used here is, it's safe to use a hub motor up to 2 1/2 times the rating for short periods of time. In the case of the BPM II, up to 1000W(constant) to 1500W(short bursts).
At any rate, the simulator @ ebike CA;
http://www.ebikes.ca/tools/simulator.html?bopen=false&motor=MBPM&cont=C35&axis=kph&wheel=700c&hp=0&mass=60
shows it reaching a top speed(no pedal) of 36 Kph.
That is;
Mountain bike
36 V
700cc wheels.
mid-speed (260) v ersion

markz · Oct 5, 2018

If you have 36V battery then that is fine!
Long Haul Trucker is the LHT by Surly
If 35kph is your goal, then going with a dependable direct drive hub motor would be good.

We need more information though.
Do you want to have pedal assist or throttle only?
How much pedaling do you want to do?
Is it for commuting, pleasure or physical activity?

22 miles (32km) route with flat terrain and a 3% grade somewhere in your route.
Lets do some keyboard math because I am bored.
You need more battery then just 32km, so lets round it up to 50km. Shallower discharges = longer battery life!

http://www.ebikes.ca/learn/batteries.html
Motor Type Rough energy usage
Minimal Assist (using motor only on hills, slower ~30kph setup) 6-8 Wh/km
Typical Assist (~40 kph with pedaling, motor on all the time) 9-12 Wh/km
Power Hungry (either no pedaling, or hauling a load, or going really fast) 14-20 Wh/km

Lets use 15Kh/km x 50 = 750Wh
750Wh divided by 36V = 20Ah to go 50km on 36V

You got 12 and 15Ah. that is 37Ah. Obviously! :wink:
But are they new, newer, old? All affects distance!

Another scenerio, 36V x 15Ah = 540Wh divided by 15Wh/km = 36km your distance is 32km. And your 12Ah is 28.8km.

Remember to store your batteries at 37V, I hope you've been doing that!

Recap, when new your batteries could do...
36V 12Ah = 29km
36V 15Ah = 36km
No need to buy a new battery, obviously. But do your battery packs have a BMS in them?

I say install your 15Ah pack on the bike or however you want to do it. Take care of it.
This is what I'd do, depending on the size of the pack. Place both batteries in parallel and have one 36V pack of 27Ah. Place it in the triangle of the frame, this will net you 65km, and you would only use half of it, making for a shallow discharge of the pack which is better then going all the way down to the LVC of the pack of 30V or 31V. Something to consider also, is maybe charge the pack only to 40V, instead of 42V which is the max. Again, longevity of the pack, want it to last forever! Obviously, but it will degrade over time, number of discharges, charges, depth of discharge etc etc etc.

markz · Oct 5, 2018

Leafbike and Leafmotor have the direct drive motors which is a great motor, plus you can get it with a KT display for your handle bar, it can also have pedal assist or you can choose no to have it. It has the speed, distance, voltage and more! I'd compare the 1500W to the 1000W in terms of size and weight and if there is no difference then buy the 1500W motor, but get someone to lace it for you where you live with good quality spokes and a rim, both available at www.ebikes.ca in Vancouver Canada.

If you dont want the drag of the direct drive motor when no power is applied, feels like a flat tire then a geared motor is good.
Then I'd suggest buying from www.ebikes.ca something like the eZee motors.
www.em3ev.com is a good place to buy from also, english guy in China
Luna Cycle is alright with their flat rate shipping, located in California.
BMSBattery is alright, with their s/h prices high, but that is why their product prices are low! Located in China.
Gosh I need to copy and paste a list, thats a good start.

erian · Oct 5, 2018

markz said:
If you have 36V battery then that is fine!
Long Haul Trucker is the LHT by Surly
If 35kph is your goal, then going with a dependable direct drive hub motor would be good.

We need more information though.
Do you want to have pedal assist or throttle only?
How much pedaling do you want to do?
Is it for commuting, pleasure or physical activity?

22 miles (32km) route with flat terrain and a 3% grade somewhere in your route.
Lets do some keyboard math because I am bored.
You need more battery then just 32km, so lets round it up to 50km. Shallower discharges = longer battery life!

http://www.ebikes.ca/learn/batteries.html
Motor Type Rough energy usage
Minimal Assist (using motor only on hills, slower ~30kph setup) 6-8 Wh/km
Typical Assist (~40 kph with pedaling, motor on all the time) 9-12 Wh/km
Power Hungry (either no pedaling, or hauling a load, or going really fast) 14-20 Wh/km

Lets use 15Kh/km x 50 = 750Wh
750Wh divided by 36V = 20Ah to go 50km on 36V

You got 12 and 15Ah. that is 37Ah. Obviously! :wink:
But are they new, newer, old? All affects distance!

Another scenerio, 36V x 15Ah = 540Wh divided by 15Wh/km = 36km your distance is 32km. And your 12Ah is 28.8km.

Remember to store your batteries at 37V, I hope you've been doing that!

Recap, when new your batteries could do...
36V 12Ah = 29km
36V 15Ah = 36km
No need to buy a new battery, obviously. But do your battery packs have a BMS in them?

I say install your 15Ah pack on the bike or however you want to do it. Take care of it.
This is what I'd do, depending on the size of the pack. Place both batteries in parallel and have one 36V pack of 27Ah. Place it in the triangle of the frame, this will net you 65km, and you would only use half of it, making for a shallow discharge of the pack which is better then going all the way down to the LVC of the pack of 30V or 31V. Something to consider also, is maybe charge the pack only to 40V, instead of 42V which is the max. Again, longevity of the pack, want it to last forever! Obviously, but it will degrade over time, number of discharges, charges, depth of discharge etc etc etc.

thanks for the reply,

I care about PAS mainly. throttle is OK if it exists i wont say no, but I wont use it, my mentality here is that if i have to use throttle i might as well take the train. The target is to commute and exercise. Both. exercise is part of why i do this but the commute has to be fast within specific time no matter if my legs are lazy that day.

I weigh 90kg, 192cm, able to produce a consistent 2,5 w/kg almost indefinitely. the 3% is nothing on a good day, but my goal here is to commute, rain or shine, faster and the motor will be there to ADD to my legs, not the opposite. Right Now I have been doing the same commute with a 250w geared MXUS which is on an old AL frame bike in 1h 15mins more or less, with 1/4 of the 15Ah battery. Reason is the battery does not really add much, cause there is no need for high torque due to the flat commute?
I nderstand that the Surly will be heavier than the Aluminum GT Frame i use now but also with a stronger motor?

SlowCo · Oct 5, 2018

A throttle doesn't mean you have to stop pedaling... :roll:

It means you can add as much or as little assist as you feel necessary at that moment. :wink:

erian · Oct 5, 2018

SlowCo said:
A throttle doesn't mean you have to stop pedaling...
It means you can add as much or as little assist as you feel necessary at that moment. :wink:

heh noob here...never used it that way...

donn · Oct 5, 2018

Yeah, one way to think of it is as a grade adjuster. Hold the throttle at 15 mph, and voilá, it's like all the uphill grades have lost their power to slow you down, so you can just pedal along in whatever gear that would be (at 15 mph.) On a steep grade the power split might be 90% motor, on the flats maybe 100% pedal. I don't know how pedal assist works, but I know people like it, so they must get used to the weirdness, but the simplicity of a plain throttle system appeals to me.

Hwy89 · Oct 7, 2018

+1 for donn. I just use enough throttle to keep a steady resistance on the pedals and most of the time use the gears to control the speed. I do pedal all the time but have found this system best for steady long distance travel. Just back from a 600 mile camping trip riding a Surly Big Dummy loaded with 90 pounds of camping gear. Longest day 100 miles.

OneJohn · Oct 14, 2018

I'm using a 36V Q100CST in the 328RPM winding with a 36V battery. My typical use is at 250W electrical power, for 200W mechanical output. On level ground with no headwind, some decent pedaling gets me to 40km/h (25mph). The ebikes.ca simulator, says motor will go up to about 350W at 40km/h, which seems correct from my usage.

It won't do much for steep hills, and isn't suitable if you're not pedaling, but it sounds about right for your usage.

25mph new build.

erian

1 mW

motomech

10 MW

markz

100 TW

markz

100 TW

erian

1 mW

SlowCo

1 MW

erian

1 mW

donn

10 kW

Hwy89

10 kW

OneJohn

1 mW

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