Insat battery voltage sag

Dave.ah

Finding my (electric) wheels
Mar 14, 2018
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2
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Tha
legality aside, I would not recommend a geared hub for anything over 25mph. The Q128H has for example a gear reduction ratio of 13.2 to 1. When you hit 28mph on a 26" wheel, the RPM is 375RPM. Thus the rotor of the Q128H will spin at 13.2 * 375RPM = 4950 RPM. Your nylon gears won't last very long.
The BPM with a reduction ratio of 5:1 will fare a bit better, 1,875RPM but you are much better off sticking with your direct drive motor. Their ball bearings will last a lot longer.
Thanks for that information. I'm still learning when it comes to hub motors. My main concern is the voltage sag knackering my battery. But even when I set my CA to 25 amps I cruise at about 20mph which only pulls 9-10 amps on the flat. So I'm not pulling 25 amps continuously anyway. And at that speed the voltage only sags 1-2v.
 

Woosh

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Tha
Thanks for that information. I'm still learning when it comes to hub motors. My main concern is the voltage sag knackering my battery. But even when I set my CA to 25 amps I cruise at about 20mph which only pulls 9-10 amps on the flat. So I'm not pulling 25 amps continuously anyway. And at that speed the voltage only sags 1-2v.
the only thing you can do to prolong the life of your battery is to set the speed limiter to lower than it is at the moment. Speed is what kills the battery.
When a cell is specified 2C, pull 1C top. That will keep the battery long life.
Your 13S5P 48V 14.5AH battery with 29E is suitable for up to 25mph speed limited cruising. if you only want to cruise at 20mph, then replacing your DD motor with the Q128H or Bafang BPM is a very sensible solution
The main benefit of changing is lesser weight and no cogging, there is no saving in battery consumption at that speed with the Q128H or SWX02 or BPM. Over 20mph, the DD motors begin to shine.
 

Dave.ah

Finding my (electric) wheels
Mar 14, 2018
16
2
Cheshire
the only thing you can do to prolong the life of your battery is to set the speed limiter to lower than it is at the moment. Speed is what kills the battery.
When a cell is specified 2C, pull 1C top. That will keep the battery long life.
Your 13S5P 48V 14.5AH battery with 29E is suitable for up to 25mph speed limited cruising. if you only want to cruise at 20mph, then replacing your DD motor with the Q128H or Bafang BPM is a very sensible solution
The main benefit of changing is lesser weight and no cogging, there is no saving in battery consumption at that speed with the Q128H or SWX02 or BPM. Over 20mph, the DD motors begin to shine.
Thanks. My cells are PF but I understand your point. Maybe I should cruise at a higher speed? Although it does draw less amps at 20mph.
 

Woosh

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May 19, 2012
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My cells are PF but I understand your point.
PF (NCA nickel cobalt aluminium) and 29E (NCO nickel cobalt) are similar in performance but do not have the same chemistry. I think PF is more stable but has slightly higher internal resistance.

Maybe I should cruise at a higher speed? Although it does draw less amps at 20mph.
No. You need to use the speed limiter to stop the controller spiking thus protecting your battery.
 

Dave.ah

Finding my (electric) wheels
Mar 14, 2018
16
2
Cheshire
PF (NCA nickel cobalt aluminium) and 29E (NCO nickel cobalt) are similar in performance but do not have the same chemistry. I think PF is more stable but has slightly higher internal resistance.



No. You need to use the speed limiter to stop the controller spiking thus protecting your battery.
I use the cruise control function on my CA I think that will do the same thing?

I've been reading up on the bafang bpm. Where is the cheapest place to buy one? I bought my son a supposed 250w 36v geared kit, although it came with a 15 amp controller so more like 500w. I really like the torque from that, plus it roles just like a normal bicycle.
 

Woosh

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this research seems promising. It may lead to much longer life for our e-bike batteries.

quote:

A novel single-ion conducting polymer electrolyte (SIPE) based on ionic liquid (IL)-decorated PMMA nanoparticles dispersed in a propylene carbonate (PC) host is reported. This SIPE possesses a superior lithium-ion transference number (tLi+) of 0.96 with an enhanced ionic conductivity of 3.13 × 10−3 S cm−1 at room temperature and a wide electrochemical window up to ∼5.18 V. The enhanced ionic conductivity is ascribed to the unique brush-like structure of ionic liquid groups tethered to PMMA nanoparticles. Furthermore, the developed SIPE was found to be more efficient in suppressing lithium dendrite formation on a cycled lithium anode. As little as 11 wt% PMMA-IL-TFSI in a LiTFSI/PC host produces more than a ten-fold increase in the cell lifetime. On the other hand, this SIPE exhibits shear-thinning behavior which can be advantageously utilized in electrolyte processing. In addition, galvanostatic cycling measurements in Li/Li4Ti5O12 half cells using this SIPE exhibit excellent rate performance. Even at an extremely high charging rate of 875 mA g−1 (5C), the capacity is still around 100 mA h g−1, that is over 57% of the theoretical capacity (175 mA h g−1). These attributes enable the developed SIPE to be a promising candidate for high-performance lithium batteries.

end quote.
 
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Thanks again. Will the 328rpm version hit 28 mph without peddling? I'm just trying to get an idea of what its like. It looks like a 250w motor which I quite like the idea of.
28 mph is the max no-load speed at which it makes zero power. Max power comes at about 21 mph. It's then a straight line down to zero at 28 mph, so 50% power ar 24.5 mph. That's all with a 26" wheel and varies with the state of the battery.
 

Dave.ah

Finding my (electric) wheels
Mar 14, 2018
16
2
Cheshire
28 mph is the max no-load speed at which it makes zero power. Max power comes at about 21 mph. It's then a straight line down to zero at 28 mph, so 50% power ar 24.5 mph. That's all with a 26" wheel and varies with the state of the battery.
Thanks that gives me a very good idea what its like. My current hub has a no load speed of about 39mph. Are there any geared hubs that can pull about 25 mph at max power? Or would it be pointless and I should just stick to my current hub?
 

Nealh

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Aug 7, 2014
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My Yosepower 36v hub maxed out at about 23mph with my gearing in 700c wheel.
28pm on pedal power achieved by over volting with 48v @20a, rpm @36v 270/280rpm. Gearing ratio 5:1, how long the hub would last at this speed is unknown.
Size wise very similar to the Q128 hubs.
 
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You can change the speed of any hub-motor by changing the voltage. Maximum speed is directly proportional to battery voltage, so the same motor will spin twice as fast at 48v as it will at 24v. Wheel size also has a direct affect.

You're always trading speed for efficiency. Any motor becomes increasingly less efficient once it drops below 50% of its maximum speed, so your 40 mph motor is extremely wasteful when you give it full power at anything below 20 mph, which is probably where it spends most of its time.
 
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Woosh

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You're always trading speed for efficiency. Any motor becomes increasingly less efficient once it drops below 50% of its maximum speed, so your 40 mph motor is extremely wasteful when you give it full power at anything below 20 mph, which is probably where it spends most of its time.
DD motors are not all that bad.
It is at speed below 10mph that DD motors suck.

This is the performance chart for the DD motor I am evaluating at the moment:

 
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Dave.ah

Finding my (electric) wheels
Mar 14, 2018
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2
Cheshire
You can change the speed of any hub-motor by changing the voltage. Maximum speed is directly proportional to battery voltage, so the same motor will spin twice as fast at 48v as it will at 24v. Wheel size also has a direct affect.

You're always trading speed for efficiency. Any motor becomes increasingly less efficient once it drops below 50% of its maximum speed, so your 40 mph motor is extremely wasteful when you give it full power at anything below 20 mph, which is probably where it spends most of its time.
Right I see. I'm coming round to the idea of a top speed of 22 mph as that's were I spend most time anyway. The Q128 you recommend, does it come in a 48v version? Or is it a 36v that's fine to run at 48v?
 
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As I already said, Q128c is 48v 328 rpm. The 36v Q128H is supposed to be 201 rpm, which would make it approx 260 rpm at 48v, though it might be actually 260 rpm at 36v because the 201 rpm Q128C is actually 260 rpm. I have a fairly old 48v 201 rpm Q128H that maxes out at 19 mph on the road.
 
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Dave.ah

Finding my (electric) wheels
Mar 14, 2018
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2
Cheshire
As I already said, Q128c is 48v 328 rpm. The 36v Q128H is supposed to be 201 rpm, which would make it approx 260 rpm at 48v, though it might be actually 260 rpm at 36v because the 201 rpm Q128C is actually 260 rpm. I have a fairly old 48v 201 rpm Q128H that maxes out at 19 mph on the road.
Thanks. I had forgotten you'd already told me that, so much to take in. Will I still be able to use one of the hall sensor wires for the speedo on my CA with a geared motor?
 
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It has a separate speed sensor in the hub. You don't really need a CA with these motors. I'd chuck it and get a KT 20A controller to go with the motor. The LCD shows power, speed, voltage, distance, etc and a really nice control system.
 

Dave.ah

Finding my (electric) wheels
Mar 14, 2018
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2
Cheshire
It has a separate speed sensor in the hub. You don't really need a CA with these motors. I'd chuck it and get a KT 20A controller to go with the motor. The LCD shows power, speed, voltage, distance, etc and a really nice control system.
Chuck it? Haha I've only had the CA a few months and I love it. I went for a ride tonight and had the speed limited to 20 mph it was only using about 250 odd watts to keep it at that speed. I've never used the speed limiter on the CA before. Nice feature.
 
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Chuck it? Haha I've only had the CA a few months and I love it. I went for a ride tonight and had the speed limited to 20 mph it was only using about 250 odd watts to keep it at that speed. I've never used the speed limiter on the CA before. Nice feature.
You can set the speed limit in the KT controller's LCD. It uses current control for the PAS and you can set the power to 5 different levels, so you get power economy as well as speed economy. I have 3 CAs and haven't used any of them since 2012.
 

Dave.ah

Finding my (electric) wheels
Mar 14, 2018
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2
Cheshire
You can set the speed limit in the KT controller's LCD. It uses current control for the PAS and you can set the power to 5 different levels, so you get power economy as well as speed economy. I have 3 CAs and haven't used any of them since 2012.
I'll have to stick with the CA for the foreseeable. My wife would string me up by my gonads if I chucked the CA haha.
 

Woosh

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The Cycle Analyst has come on a long way in six years. Maybe you should check out some of the changes since you last used one.
masochist :)
what can it do more than a cheap KT LCD?