Motor & Battery Combination.

Woosh

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May 19, 2012
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OK, I'm going to make a purchase over the next week or so. Before I go any further, I've leaned toward a Mid Drive system, but I'd like to hear about the pro's and con's of a rear hub drive. The lower prices suggest that maybe they have become a little obsolete, but I'm an absolute novice so any guidance will be appreciated.

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Pete
vfr400 made the case for hub drives. Let me make the case for mid drives.
1. there is not much difference in reliability and maintenance cost between the two types.
2. there are less variables in installing a mid drive compared to a hub drive. If you can remove the bottom bracket, then you are half way there with a mid drive.
3. the quality of a 48V TSDZ2 with or without throttle is difficult to match. It is lightweight, very quiet, has a wide torque range especially at low speed, best weight distribution and natural ride feel.
 

KirstinS

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Apr 5, 2011
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vfr400 made the case for hub drives. Let me make the case for mid drives.
1. there is not much difference in reliability and maintenance cost between the two types.
2. there are less variables in installing a mid drive compared to a hub drive. If you can remove the bottom bracket, then you are half way there with a mid drive.
3. the quality of a 48V TSDZ2 with or without throttle is difficult to match. It is lightweight, very quiet, has a wide torque range especially at low speed, best weight distribution and natural ride feel.
1. This is my experience too . But I'm not sure I can agree from anecdotal evidence from this site at any rate.

2. I totally agree.

3. Never tried one so cannot comment. I just dont want a torque sensor as I want to choose how lazy or dynamic I wish to be, crucially, whilst keeping same speed
 
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Woosh

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1. This is my experience too . But I'm not sure I can agree from anecdotal evidence from this site at any rate.
the main issue was with the 25A BBS02 - if you lose 30% yield when climbing a steep hill in the wrong gear, imagine how quickly the motor can overheat.
No such problem with the BBS01B ever since Bafang locked the maximum current draw to 15A.
3. Never tried one so cannot comment. I just dont want a torque sensor as I want to choose how lazy or dynamic I wish to be, crucially, whilst keeping same speed
you can get the TSDZ2T with throttle.

This said, I choose a hub drive any day for commuting.
 
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PeterPi

Finding my (electric) wheels
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Hi. I have looked closely at your climbs. On the second chart, coming back from the next village, you will be climbing approx 270 feet (130 -400 feet) over a distance of about .6 mile (3168 feet) which works out at a grade of over 8%.
Now, I personally have difficulties with such grades as it takes a few minutes of puffing and panting to assist my hub motor over such a grade. Then again, I am overweight (90kg) and heading for 64, but I am sure other people have no problems.
Slightly heavier and older. :)
 

Sturmey

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Slightly heavier and older. :)
The woosh website gives useful charts that (in my view) gives a good indication of what performance to expect where the rider is not able to contribute much power. Now taking into account that you can sometimes be facing a headwind as well as an over 8% climb, and you do not want to be climbing that hill at 3.5 mph (which overheats motor and controller), then I reckon a good choice would be the crank motor in that if it can propel a 75kg rider up a 15% hill, it should be well capable of dealing with a heavier rider on an 8-10% hill (TCM crank motor). However, I have had experience with 4 different hub motors so far but no experience of any cd motors.
http://wooshbikes.co.uk/?motorcharts
 
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PeterPi

Finding my (electric) wheels
Oct 1, 2019
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If you have 36v, you can solve that by going up to 48v, which will give you 33% more torque. If you have steep hills, want a hub-motor and aren't a club cyclist, 48v is mandatory. I find it really surprising that manufacturers have more or less standardised on 36v, when 48v costs the same, is more efficient and gives more power options.
Yes I can see that more volts is less amps for the same power. Less likelihood of losses cause by cabling and joints. Definitely a consideration. So many helpful posts, I'm glad I came here and I'm glad I asked.
 

Woosh

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However, I have had experience with 4 different hub motors so far but no experience of any cd motors.
A hub motor works effectively as a CD motor stuck on one of the middle gears.
 
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sjpt

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Sturmey

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Thanks, useful link I hadn't seen before. For much more varied charts see https://www.ebikes.ca/tools/simulator.html
The motor simulator is very good. For the purposes of comparison, I have compared a 95 kg 'not as fit' cyclist (50w legs)with a 75 kg fit cyclist (200w legs), both with bikes weighing 25kg and facing a 8% hill. The lighter fit cyclist will ascend at 20.4 kph (12.8 mph) and the not so fit heavier cyclist at 9.7kph (6.1 mph).
Notice also that the motor on the slower bike will consume 21.2 amps (although controller is 14 amps battery current max). This is due to 'flywheel/flyback current' and will heat up the motor and controller. So its really important to take the weight and fitness of the cyclist into account.


motor.jpg
 
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anotherkiwi

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Jan 26, 2015
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The motor simulator is very good. For the purposes of comparison, I have compared a 95 kg 'not as fit' cyclist (50w legs)with a 75 kg fit cyclist (200w legs), both with bikes weighing 25kg and facing a 8% hill. The lighter fit cyclist will ascend at 20.4 kph (12.8 mph) and the not so fit heavier cyclist at 9.7kph (6.1 mph).
Notice also that the motor on the slower bike will consume 21.2 amps (although controller is 14 amps battery current max). This is due to 'flywheel/flyback current' and will heat up the motor and controller. So its really important to take the weight and fitness of the cyclist into account.


View attachment 32377
If you had chosen a 26" wheel the fit guy would climb at the cut off - personal experience on a 9.4% average climb - 20 km/h on the gnarly bits up to 13%. And contrary to those who ride a hub motor badly it helps a lot to be in the correct gear.

I have a couple of spots on my commute which flirt with 16-17% and can't top 16 km/h there in the correct gear with my mid-motor. If I drop down a gear of course I go slower - 14 km/h ish - but both battery and motor thank me for thinking about their health.
 
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PeterPi

Finding my (electric) wheels
Oct 1, 2019
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PeterPi, do youself a favour and arrange a test ride (or two) with Halfords in Llansamlet.
Aye, I suppose a ride down to the Liberty and back might be a decent test.
Any of their bikes give you a feel for what a conversion is going to be like?
 

Hightechpete

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Jan 20, 2018
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Any of their bikes give you a feel for what a conversion is going to be like?
Don't know what they've got in the way of demos, tell them you can't decide between crank or hub drive, maybe they'll let you try both. I've never ridden a crank drive so I can't comment, all bikes ride diffently but there is not a huge difference between rear drive 250watt motors so it will give you a pretty good impression of what to expect.
 
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PeterPi

Finding my (electric) wheels
Oct 1, 2019
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I have a couple of photos here. Does this look like its compatible with most/any mid drive kit?Bike 1.jpgBike 2.jpg

Thanks
Pete
 

Nealh

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Looks good plenty of chain wheel clearance to rear stay.
The only thing you may find is the inside of the BB shell may need cleaning up (weld nibs removing or over any weld ) with a file or Dremel type tool.
 
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