Lightweight/discrete Q128c commuter build on a road bike

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ModeratelyFastF   10 mW

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Lightweight/discrete Q128c commuter build on a road bike

Post by ModeratelyFastF » Mar 08 2018 7:10pm

Edit: A preview of where this build ended up:

Q100C motor
S12S BMSBattery controller
SLCD3 display
EM3EV 52V 721Wh battery

Image

Original post:

Hi all, I'm looking to build a reliable, lightweight, discrete commuter build. Ideally it would be full stealth: silent, motor so small most people would miss it, and small battery in a bag on the frame that isn't obviously a battery. Here are the constraints:

Desired max speed on level ground: 40-45km/h
Desired max range at what cruising speed: 32km (20mile) round trip commute (ie 16km each way). Would like to average 35km/hr.
Wheel size: 700c
Base bike: 12kg aluminium road bike with 135mm drop outs
Brake type: V-brakes
Rider weight: 80kg + 5kg bag = 85kg load
Riding style: I will be peddling - currently average 25kph/15mph over my commute (and about 32kph on the flat)
Terrain: mostly flat, some short hills under 15% grade
Budget: something reasonable!

I don't have any experience putting ebikes together (or for that matter regular bikes beyond basic maintenance) so I probably need some hand holding. Here is my plan so far:
My questions:
  1. I have a 10sp shimano cassette, can I just swap that onto the wheel from BMS?
  2. To install the PAS sensor do I need special tools?
  3. Will that motor work ok in 700c wheels, or is it going to overheat if I can't keep my average speed up? At present I average 25kph over the whole commute, and I'd hope to at least average 30kph with the motor.
  4. If I take the battery off can I ride it like a normal bike, or will the Q128c create a lot of friction/drag? If so I might get a second 10sp cassette so I can swap the whole wheel over if required.
  5. Is that battery ok, or is it overkill for my commute? If I could get by with a smaller battery I could hide in a bag that would be even better, but I understand that would involve getting a separate controller.
  6. Is there anything else I need to make this work?
Any help appreciated!
Last edited by ModeratelyFastF on Jun 21 2018 9:40pm, edited 2 times in total.

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by zro-1 » Mar 08 2018 8:20pm

You can take a look at my build thread for some ideas. I am using the slightly smaller Q100H, but I got a motor that was the wrong gearing so it's a little too fast, and not quite strong enough for what I wanted as my ideal setup. I think you can probably go with the slower 201 RPM model in a 700c wheel if you're going to have a 48V/20A system and still hit 40kph without too much issue. My faster 328 RPM motor at 48V/20A is hitting 45-48kph.

I'm going to be swapping out the already small Q100 for an even smaller Xiongda YTW-06 in a few weeks.
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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by markz » Mar 08 2018 10:01pm

Your goal is to force yourself to pedal, or hide the motor?

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by ModeratelyFastF » Mar 08 2018 10:28pm

zro-1 wrote:
Mar 08 2018 8:20pm
You can take a look at my build thread for some ideas. I am using the slightly smaller Q100H, but I got a motor that was the wrong gearing so it's a little too fast, and not quite strong enough for what I wanted as my ideal setup. I think you can probably go with the slower 201 RPM model in a 700c wheel if you're going to have a 48V/20A system and still hit 40kph without too much issue. My faster 328 RPM motor at 48V/20A is hitting 45-48kph.

I'm going to be swapping out the already small Q100 for an even smaller Xiongda YTW-06 in a few weeks.
Thanks mate, in fact I'd already read through your thread :) I liked your small battery, but was sorry to see you didn't like it mounted on the bike. I really want the battery on the bike for convenience, and although I'd love a smaller stealthy battery like you built, I haven't located anything that would work.

When you say it was too fast and not strong enough, did that mostly manifest as the motor struggling up hills? Or was it just getting too hot in general?

On the Xiongda motor, I've heard it's quite noisy. I really like the fact the Q128c is pretty quiet.
markz wrote:
Mar 08 2018 10:01pm
Your goal is to force yourself to pedal, or hide the motor?
My goal is to keep weight down, look/sound stealthy if possible (although my current battery choice isn't stealthy), and go faster than I can currently under my own steam. I would nearly always be doing some peddling, it's just that at the end of a 12hr night shift I've lost about half my power and need some help to keep my speed up!

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by dogman dan » Mar 09 2018 8:12am

One of the hard to understand things about e bikes is how much more speed effects drag. You'd think enough power to go 5 kph would be enough to go 5 kph faster if you already pedal fast.

But in fact, it takes 4 time more than that, or more. Pedaling briskly, you will still tend to pull 500-600 watts from your battery to cruise 32 kph. ( 20 mph) WTF? it only takes 400w to cruise 20 mph. Yes, on perfect flat ground, with no wind. Your commute will sometimes pull 300w, sometimes 900. And when its cold, your battery effectively shrinks in size. Cold day, uphill, into wind, now you are truly hozed. My route was downhill one way, up the way back. But if you have rolling hills, that will not affect range as much. But a ride home into wind will blow your battery budget. What really gets to sting is when the weather changes, and you get to ride into wind both ways.

So what I'm trying to say is you need about 1 ah per mile for that commute. Many days you will only use 2/3 of that, but later on as the battery ages it loses some of that original capacity too.

Everything in your plan is fine, but I think a battery 13-15 ah in size would work better, unless you can charge at work.

The motor won't resist much, but the weight of it and the battery will, so you may not pedal with the motor off as much as you think. You will get a nice coast and or easy pedaling downhill of course.

Another way to miser your battery, and run a smaller size is to stick to the speed you have now. Its utterly unbelievable how much you save riding just 18 mph instead of 20 mph. At 25kph/ 15 mph, you can easily do the ride with a 10 ah pack.

That's also more stealthy, when you ride like a racer on a commute, you don't look like a racer, you look like a fast e bike.

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by ModeratelyFastF » Mar 10 2018 1:48am

Thanks mate, I appreciate the thoughtful response, I hadn't really thought through the real world energy requirements. Charging at work would be problematic unfortunately, so I need to have a battery sized for a return trip.

I've seen a few comments around Endless Sphere that imply an active riding style could make my commute work with 11.5ah battery. For example, molybdenum was getting about a 50km range with an active riding style on a Q128c and a 11.45ah 48v battery. That was on the 201rpm motor though, and he felt he was putting more energy in than the motor a lot of the time.

Perhaps a Q128c at 201rpm would be enough. d8veh said this:
d8veh wrote:
Jul 05 2017 4:13am
I just recently converted my bike with a Q128C. I love it. It's powerful, smooth and silent. I'm using the 36v 201 rpm one at 48v with a 14 amp sine wave KT controller. I get a top speed on the road of about 38km/h with 26"wheels. I think the most suitable controllers,if you want more power, are the 17A and 20A sinewave ones you get from PSWpower.
I assume with a 20a controller I'd manage a top speed of at least 38km/h on a road bike frame?

Ultimately I probably wouldn't bother with the ebike if I can't increase my average speed from 25kph over the commute to at least 30kph - might as well just save my money, run a non-assisted bike, and get some more exercise!

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by zro-1 » Mar 10 2018 11:49am

ModeratelyFastF wrote:
Mar 08 2018 10:28pm
When you say it was too fast and not strong enough, did that mostly manifest as the motor struggling up hills? Or was it just getting too hot in general?
The motor hasn't gotten hot to the point that I was ever concerned about it. It only gets slightly warm right now. It's still pretty cool here in Atlanta, so I'm riding in 35-65º F temperatures. I'm not sure how much warmer it might get once temperatures reach 85-90º F. But I don't think it'll ever get hot enough for me to be worried about it. My issue is the torque and particularly the gearing.

I had ordered the slower geared motor but ended up receiving the fast 328 RPM model. This gearing in a 700c wheel makes starting on uphill slopes pretty tricky. On top of the gearing, the hall sensors in my motor are defective, so I need to run sensorless which causes there to be about a second delay before the motor starts. So when I'm getting going from a stop and headed uphill I really have to stand on the pedals to get rolling before the motor kicks in and helps (I'm on a single-speed, so if you have gears that may not matter).

At the other end of the spectrum, when I'm on a flat stretch, the motor gets the bike going too fast to pedal along with. I'm using a Phaserunner FOC controller. This type of controller will always gets to top speed regardless of how much throttle you give it. The throttle only determines how quickly you'll get up to top speed. So even when I just give it a 1/4 turn of the throttle it eventually gets going too fast to keep up with. I don't mind that behavior, but a slightly lower top speed would be ideal for me (without needing to lower the voltage into the motor).

I would probably be happy with the Q100 if I had functioning hall sensors and the lower gearing. Instead of ordering another motor though, I decided to give the YTW-06 a chance since it seems to be a more modern design and I could order it from the factory to fit a 120mm wide rear fork width. Also, with the bad luck I had with the motor I received from the seller, I don't really want to order from them again. That's just my experience though. Many people have this motor or the Q128 and love them.
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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by molybdenum » Mar 10 2018 3:17pm

ModeratelyFastF wrote:
Mar 10 2018 1:48am

I've seen a few comments around Endless Sphere that imply an active riding style could make my commute work with 11.5ah battery. For example, molybdenum was getting about a 50km range with an active riding style on a Q128c and a 11.45ah 48v battery. That was on the 201rpm motor though, and he felt he was putting more energy in than the motor a lot of the time.

Perhaps a Q128c at 201rpm would be enough.
I’ve been doing a daily commute of 30 km for the past two years on the Q128c (201RPM@36V) using a 48V 11.5 Ah battery, and I’ve never come close to running out of juice. For the worst case scenario: on cold days (-4C of 25F is cold for this part of the world) with a stiff headwind both directions and using metal studded tires, I have depleted my battery by 85-90% over my 30 km commute. For most days, my riding style + battery supports a 50 km range.

What I do to ensure I have battery capacity for my commute is to limit amps to 10 for a max of ~500W; I try to use as much pedal power as possible, aiming to keep actual wattage to 200-300W for most of my commute. This works in the spirit of my build, which is to still get lots of exercise and augment leg power to achieve faster commuting times. On days where I’m not feeling so swell, I leave a bit early and travel 5 kph slower to use same battery with less pedal power. On days where I’m feeling strong, I can see my motor wattage at WOT approach zero as I reach the motor’s unloaded RPM on slight descents, and will remain around 300W at WOT on level ground.

I have never tried a faster wind motor, and for an athletic rider with a flat commute, this would make sense, as I could likely achieve 5 kph gains with slightly more motor power. Unfortunately, my commute is very hilly, and my gains on descents would likely be offset by loss of torque on the ascents. The current motor is a reasonable compromise.


ModeratelyFastF wrote:
Mar 10 2018 1:48am
Ultimately I probably wouldn't bother with the ebike if I can't increase my average speed from 25kph over the commute to at least 30kph - might as well just save my money, run a non-assisted bike, and get some more exercise!
As average speed, this is a very difficult comparison. My route has constant rolling hills, many stop signs, traffic lights and there are areas where I must travel slowly to make my way past cars backed up several city blocks. On the rare day where I make most of the traffic lights and don’t have to fuss with dense traffic, I have done the 15 km commute in just under 30 minutes for an average speed of 30 kph, and depleting my battery by around 60% over the 30 km distance. Most days, it takes me around or just over 35 minutes each way. I have done this route in less than 35 minutes unpowered on a fast racing bike but the effort leaves me KOd for the rest of the day – an ebike is definitely better.
2012 Kona Dew Deluxe, Q128C and 9spd cassette, S12S sinewave controller, 48V Panasonic battery

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by zro-1 » Mar 10 2018 8:35pm

molybdenum wrote:
Mar 10 2018 3:17pm
As average speed, this is a very difficult comparison. My route has constant rolling hills, many stop signs, traffic lights and there are areas where I must travel slowly to make my way past cars backed up several city blocks.
I agree with this completely. On my commute half my ride is rolling hills, and the other half is lots of stop signs and traffic lights with stretches where I need to navigate through stop-and-go traffic. For me, the electric motor is more about making those hills and constant stop and go easier. When I do go somewhere flat with no stops, I generally don't use the motor at all, or only use it at it's lowest power levels (FOC throttle works like variable PAS levels). The side-effect of that help is that I maintain a higher average speed for the total length of my commute. Having made several trips back and forth on this current setup, I'm averaging 17 mph (27 kph) for the whole commute, but half of it is slower (14 mph average) and the other half is faster (20 mph average). I'll hit top speeds of 30-35 mph, but that's just for short downhill spurts.
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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by ModeratelyFastF » Mar 10 2018 9:16pm

Sounds like my commute is pretty flat in comparison (130m or 400ft elevation gain, 100m or 300ft loss, split over about 4 hills over the 16kms or 10 miles). Also I ride about 10kms on smooth dedicated bike paths, and probably only have a dozen roads where I have to yield (although there's usually very little traffic atbthe times I ride). On several occasions I've ridden to work without having to stop once and without interacting with a single car.

If I did get the 328rpm Q128c and I used it on a low level of pedal assist with a sinewave controller I assume the top speed (and wattage used) would cover the range of speeds the 201rpm winding would cover, with the option for higher top speed if desired?

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by wturber » Mar 11 2018 12:53am

ModeratelyFastF wrote:
Mar 10 2018 1:48am

I assume with a 20a controller I'd manage a top speed of at least 38km/h on a road bike frame?

Ultimately I probably wouldn't bother with the ebike if I can't increase my average speed from 25kph over the commute to at least 30kph - might as well just save my money, run a non-assisted bike, and get some more exercise!
When you say average, are you referring to the total trip speed, or your typical riding speed? To average those speeds over a typical trip, you need to spend a fair bit of time between 30 and 40 kph assuming that you have stop signs and traffic lights to deal with. I'm able to trip average 30 kph (nearly 20 mph) with little trouble using my cheapo direct drive motor on a heavy mountain bike. I typically use 25 wh/mile or less. Based on your goals, I think that's a reasonable figure to use to estimate how much battery you need. But after you do that, you should add about 50% capacity as Dogman suggests to give you a buffer for those bad days, to allow you to not fully charge the battery regularly and thus extend its life, to give yourself extra range for short lunch trips, to give yourself extra range for other kinds of trips, and to extend the battery's life by not fully discharging it frequently. My pack size was chosen to deal with a 30 mile round trip commute. But I can go about 50 miles if I ride conservatively. Having that reserve is nice when the wind is blowing strong some night, you just don't feel very energetic, and the hills somehow became steeper.

If I were you, I'd assume about 10a actually needed but then would add another 5a for the additional buffer. So a 15 or 16 amp battery for a 48 volt system would be what I'd shoot for given your goals. That said, you could probably get by with less. But personally, I like having the extra buffer.
"Commuter - DC Booster"
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8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by ModeratelyFastF » Mar 11 2018 1:20am

25kph is my average speed including lights, stop signs, hills etc - just the total distance divided by the total time as reported by my trip computer. If I really push I can sustain 35-38kph on the flat in good conditions, bringing my average trip speed up to around 27kph. I only bring that up as I want to be going at least that fast.

Based on what you guys are saying I probably should be looking at a 14-15ah battery, but the weight, cost and complexity starts to add up then - with the 11.5ah battery I linked in my first post the controller was integrated making for a neat and tidy install.

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by molybdenum » Mar 11 2018 4:18am

ModeratelyFastF wrote:
Mar 11 2018 1:20am
25kph is my average speed including lights, stop signs, hills etc - just the total distance divided by the total time as reported by my trip computer. If I really push I can sustain 35-38kph on the flat in good conditions, bringing my average trip speed up to around 27kph. I only bring that up as I want to be going at least that fast.

Based on what you guys are saying I probably should be looking at a 14-15ah battery, but the weight, cost and complexity starts to add up then - with the 11.5ah battery I linked in my first post the controller was integrated making for a neat and tidy install.
If you haven't already seen this, I recommend reading the thread by chas58: viewtopic.php?f=3&t=49691&hilit=fast+road. These builds are very similar to what you are looking for, and he's mostly using the smaller Q100 360RPM@48V in 700c wheel. You'll get a good idea at how much range/speed a super fit cyclist can get from various batteries/motor setups.

I can see that your commute is about 2 km longer than mine. To put it into context, if you were to use an average of 300W for your 1 hour 5 minute 2-way commute (30 kph average speed) your power consumption would be 325 Wh; this would be roughly 60% of the 534 Wh capacity of the 11.6 Ah BMSB battery you link. Being a fit cyclist who will augment significant leg power with a bit of motor, you'd probably be alright with 11.6 Ah - it works for me. That being said, it may be safer to have excess capacity for those lousy days. Although the 11.5 Ah BMSB battery (with Panasonic PF cells) you link does have an internal controller, you can have the same weight battery from EM3EV in 12.4 or 13.4 Ah options, as they are constructed from higher capacity cells such as Samsung 33G, 35E or LG MJ1 18650 cells. Unfortunately, you'd need an external sine wave controller, as the EM3EV batteries do not come with internal controllers:
https://em3ev.com/shop/preditor-l-47v-8 ... rrency=USD (and select one of the 13.6 Ah options).

Although having an external controller does seem to add complexity and is less stealthy, the advantage of an external controller is it is much more easily replaced should it break. Controllers are a part that are apt to fail, and I feel safer knowing I can easily swap mine for a new one should something go wrong. Since the parts from BMSB are super cheap and shipping is the main expense, I tend to order spares and have a spare controller, throttle, SLCD etc to avoid down-time (especially important if you don't have a spare bike and rely on it for the commute). The external sine wave controllers from BMSB are plug and play with the SLCD screen and motor, and their kits can be used with any battery. I hide my external controller in a small under-seat bag, which is a no-no but I'm only pulling 200-300W so it doesn't overheat even on the hottest days.

The general consensus here is that EM3EV is a reputable company with good quality batteries and that they stand behind their products.
2012 Kona Dew Deluxe, Q128C and 9spd cassette, S12S sinewave controller, 48V Panasonic battery

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by MonkeyWrench » Mar 18 2018 3:26am

ModeratelyFastF wrote:
Mar 08 2018 7:10pm
My questions:
I have a 10sp shimano cassette, can I just swap that onto the wheel from BMS?
To install the PAS sensor do I need special tools?
Will that motor work ok in 700c wheels, or is it going to overheat if I can't keep my average speed up? At present I average 25kph over the whole commute, and I'd hope to at least average 30kph with the motor.
If I take the battery off can I ride it like a normal bike, or will the Q128c create a lot of friction/drag? If so I might get a second 10sp cassette so I can swap the whole wheel over if required.
Is that battery ok, or is it overkill for my commute? If I could get by with a smaller battery I could hide in a bag that would be even better, but I understand that would involve getting a separate controller.
Is there anything else I need to make this work?
Your post inspired me to finally get a summary up of my latest build, a light (<30 lb) drop bar cyclocross bike with a Q100C: viewtopic.php?f=6&t=93328

I yammer on at length there about how the bike's been performing, might be worth a look as it sounds similar to what you're aiming for. It sure is stealthy, and fulfilled my goal of upping my average commute speed versus my unpowered road bike.

It sounds like you're a pretty strong cyclist already. You might consider the Q100C versus the Q128C. It shaves some weight and so far for me handles the power/assist levels I've been asking from it just fine. I think the Q100 is just under 1 kg lighter, which is nothing to sneeze at if you're putting in a lot of your own power.

To help with your questions:

1- I'm running a 10 sp cassette on the Q100C, works great. Actually less fussing getting the caliper aligned than on my other builds. Heck I didn't even have to re-index my derailleur!

2- Some PAS sensors are split so you can install without pulling the cranks. But I really don't care for PAS on this type of build, I prefer throttle to finely tune & feather in the assist over my effort. Sadly there has yet to be an elegant solution to throttles on drop bar bikes, I've been using a thumb throttle stuck where I can reach it from the hoods.

3- I've ridden mine pre and post conversion without using assist, I assume the Q128 is comparable. There is a small amount of drag over a bare hub but not enough to discourage me going long stretches when riding with friends on unpowered road bikes at a good clip.

4- I go 16 miles (26km) on 12s/44.4v lipo at 5 Ahr (222 Whr nominal) one way, charging both ends. I usually use about 120 Whr total (7-9 Whr/mile (5-6 Whr/km) riding the bike as an assist to keep my average speed up to 18-20 MPH (29-32 KPH). My normal road bike average speeds are 14-16 MPH (23-26 KPH). I'm sweating pretty hard either unassisted or on the ebike, but I do appreciate the ebike assist on those recovery days or when the weather is really awful!

Note that this consumption is much better than my heavy direct drive mountain bike at about 25 Whr/mile (16 Whr/km) - I was pleasantly surprised just how efficient a light drop bar ebike (combined with athletic pedaling) can be. I keep telling myself to use more juice but I currently don't have a heads-up wattmeter display so I tend to "conserve".

Using the higher speed 328 RPM motor I also peak out at about 30 MPH (48 KPH) periodically which is a lot of fun and helps push that average speed. Using the slower speed motors would not be nearly as much fun for me and how I ride. About 800 feet of elevation gain on the net uphill leg with some mild hills. The upshot of all that is yes, personally I would go against the grain a bit here and call that battery somewhat overkill (but remember, I'm putting a lot of leg into it, ebike or not). However if your choice is between that one and something even larger I would caution going against the spirit of your build trying to accommodate a large pack.

As I note in my build thread I'm using some pretty dated lipo tech because it was on the shelf- there is some more energy dense stuff out there (Turnigy Multistar in particular) that could significantly extend range. BUT then you're going down the lipo road which requires caution and close attention to safely use. Hobby grade lithium cobalt oxide (aka lipo) has always been cheap and powerful which is why so many ES'ers use the stuff. However, the newer lithium chemistries available in the cylindrical format 18650 and 20700 cells are very exciting as they finally can achieve usable power levels at high energy densities even in a small pack appropriate for a build like this.
#1 GT i-drive 5- 12s LiPo, yescom 48v1000w kit- stolen
#2 Kona Stinky Dee Lux-18s LiPo, MXUS 2806 DD, 12 fet from em3ev- retired
#3 Gary Fisher Hoo Koo E Koo-12s LiPo @ 10 Ahr, MXUS 2806 DD, 12 fet from em3ev- in use
#4 Specialized Crossroads-12s LiPo @ 10 Ahr, Bafang SWXH, 6 fet from em3ev- retired
#5 Foundry Harrow cyclocross-12s LiPo @ 5 Ahr, Cute Q100C 328RPM, 6 fet from em3ev- in use

Commute ~32 mi roundtrip in Seattle

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by ModeratelyFastF » Mar 18 2018 7:22pm

molybdenum wrote:
Mar 11 2018 4:18am
I can see that your commute is about 2 km longer than mine. To put it into context, if you were to use an average of 300W for your 1 hour 5 minute 2-way commute (30 kph average speed) your power consumption would be 325 Wh; this would be roughly 60% of the 534 Wh capacity of the 11.6 Ah BMSB battery you link. Being a fit cyclist who will augment significant leg power with a bit of motor, you'd probably be alright with 11.6 Ah - it works for me.

Although having an external controller does seem to add complexity and is less stealthy, the advantage of an external controller is it is much more easily replaced should it break. Controllers are a part that are apt to fail, and I feel safer knowing I can easily swap mine for a new one should something go wrong. Since the parts from BMSB are super cheap and shipping is the main expense, I tend to order spares and have a spare controller, throttle, SLCD etc to avoid down-time (especially important if you don't have a spare bike and rely on it for the commute). The external sine wave controllers from BMSB are plug and play with the SLCD screen and motor, and their kits can be used with any battery. I hide my external controller in a small under-seat bag, which is a no-no but I'm only pulling 200-300W so it doesn't overheat even on the hottest days.

The general consensus here is that EM3EV is a reputable company with good quality batteries and that they stand behind their products.
Thanks so much for the continued help and advice, I really appreciate it.

Based on the last few months of commuting I find I always have good power in my legs for at least one leg of the commute, with the post nightshift rides the ones where I struggle a bit (average speed drops to around 22-23kph), so I suspect my Wh usage will be somewhere between 150-330Wh on average. Thus I'm optimistic 534Wh from a 11.5Ah battery will be enough.

I certainly take on board your comments about the advantages of a bigger battery and a separate controller, and in fact I probably will buy a spare separate controller no matter which way I go. I really do want to keep things streamlined for my first build though, and I'm starting to firm up on the 11.5Ah battery with integrated controller.
MonkeyWrench wrote:
Mar 18 2018 3:26am

Your post inspired me to finally get a summary up of my latest build, a light (<30 lb) drop bar cyclocross bike with a Q100C: viewtopic.php?f=6&t=93328

I yammer on at length there about how the bike's been performing, might be worth a look as it sounds similar to what you're aiming for. It sure is stealthy, and fulfilled my goal of upping my average commute speed versus my unpowered road bike.

It sounds like you're a pretty strong cyclist already. You might consider the Q100C versus the Q128C. It shaves some weight and so far for me handles the power/assist levels I've been asking from it just fine. I think the Q100 is just under 1 kg lighter, which is nothing to sneeze at if you're putting in a lot of your own power.
Hey MonkeyWrench, thanks so much for your post, it's really helpful!

Yes if I don't need the extra weight of the q128c I certainly would be keen to avoid it. I'd heard the q128c was nearly silent which I liked. I also wondered if it might go a bit better up the hills and provide a bit more assistance when my legs are really dead. Just when I thought I was homing in on my final setup I have another factor to consider!
To help with your questions:

1- I'm running a 10 sp cassette on the Q100C, works great. Actually less fussing getting the caliper aligned than on my other builds. Heck I didn't even have to re-index my derailleur!

2- Some PAS sensors are split so you can install without pulling the cranks. But I really don't care for PAS on this type of build, I prefer throttle to finely tune & feather in the assist over my effort. Sadly there has yet to be an elegant solution to throttles on drop bar bikes, I've been using a thumb throttle stuck where I can reach it from the hoods.

3- I've ridden mine pre and post conversion without using assist, I assume the Q128 is comparable. There is a small amount of drag over a bare hub but not enough to discourage me going long stretches when riding with friends on unpowered road bikes at a good clip.

4- I go 16 miles (26km) on 12s/44.4v lipo at 5 Ahr (222 Whr nominal) one way, charging both ends. I usually use about 120 Whr total (7-9 Whr/mile (5-6 Whr/km) riding the bike as an assist to keep my average speed up to 18-20 MPH (29-32 KPH). My normal road bike average speeds are 14-16 MPH (23-26 KPH). I'm sweating pretty hard either unassisted or on the ebike, but I do appreciate the ebike assist on those recovery days or when the weather is really awful!

Note that this consumption is much better than my heavy direct drive mountain bike at about 25 Whr/mile (16 Whr/km) - I was pleasantly surprised just how efficient a light drop bar ebike (combined with athletic pedaling) can be. I keep telling myself to use more juice but I currently don't have a heads-up wattmeter display so I tend to "conserve".

Using the higher speed 328 RPM motor I also peak out at about 30 MPH (48 KPH) periodically which is a lot of fun and helps push that average speed. Using the slower speed motors would not be nearly as much fun for me and how I ride. About 800 feet of elevation gain on the net uphill leg with some mild hills. The upshot of all that is yes, personally I would go against the grain a bit here and call that battery somewhat overkill (but remember, I'm putting a lot of leg into it, ebike or not). However if your choice is between that one and something even larger I would caution going against the spirit of your build trying to accommodate a large pack.

As I note in my build thread I'm using some pretty dated lipo tech because it was on the shelf- there is some more energy dense stuff out there (Turnigy Multistar in particular) that could significantly extend range. BUT then you're going down the lipo road which requires caution and close attention to safely use. Hobby grade lithium cobalt oxide (aka lipo) has always been cheap and powerful which is why so many ES'ers use the stuff. However, the newer lithium chemistries available in the cylindrical format 18650 and 20700 cells are very exciting as they finally can achieve usable power levels at high energy densities even in a small pack appropriate for a build like this.
Thanks so much for helping with those questions! On point 4, when you're feeling a bit flat, could you safely let your cruising speed drop to around 27-30kph letting the motor do the majority of the work, or would you say that's a bad idea? I wonder if the q128c might be happier in this scenario where I need a bit more assist.

So at present I'm thinking of sticking with the 48v 11.6ah Bottle-09 battery (https://bmsbattery.com/ebike-battery/68 ... ttery.html) and now just need to decide if I go with the q100c or the q128c. I'm leaning towards the q128c as I feel it may be capable of providing a bit more assist when my legs are dead, but if I'm wrong there I may go for the q100c.

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by zro-1 » Mar 18 2018 8:53pm

Just commenting about the noise: a sine wave or FOC controller will make the biggest difference in motor noise. The Phaserunner is a FOC controller, and with the fast Q100H I can still hear the chain creak when I'm powering up a hill over the motor noise. I'm not sure if the Q128 is really quieter, but with that sine wave controller that comes in the battery you're considering, I think either motor will be very quiet... to the point that I'd take the weight savings over any sound difference.
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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by ModeratelyFastF » Mar 18 2018 11:46pm

Ok cool, thanks for clarifying the noise situation, it sounds like it shouldn't factor in to my decision.

In MonkeyWrench's build it looks like he is using 2x 6s lipos. Does that then equal 2x22.2v = 44.4v? Does that mean his motors unloaded rpm is (44.4/36) * 328 = 404rpm?

If I was to go for the 36v q100c at 328rpm and pair it with a 36v battery I'm worried I won't be able to hit the same sort of speeds MonkeyWrench is talking about.

Here's my current decision point:
  • is the 328rpm 36v q100c strong enough to move 102kg (total weight = bike (12.5kg) + me (78kg) + backpack (~5.5kg) + motor (2kg) + battery (4kg)) at a decent speed with a 36v battery?
  • Or would the 328rpm 48v q128c with a 48v battery be a safer bet (total weight 103kg, extra kg for bigger motor)?
It seems like saving 1 kg on the motor weight (less than 1% of the total weight) for what may be compromised hill climbing ability and top speed isn't such a good trade off, or am I missing something?

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by MonkeyWrench » Mar 19 2018 12:36am

No problem, glad to help! Sorry to have thrown a little loop with the Q100/Q128 comparo~

I concur at these power levels the Cute is pretty darn quiet and I'm using one of the old school square wave controllers. Just about anything more modern, including the sine wave BMS Battery one should be even quieter.

Correct you definitely want 48V if you'd like to hit those same speeds I do on 12s lipo (nominally 44.4v although freshly charged it is 49.2v). On 36v either the Q100 or Q128 will run slower (see simulator link below). As you probably know the basic rule of thumb is amps (really total Watts aka power) = acceleration, voltage = speed.

Good question regarding the Q128 vs Q100 providing most (all?) assistance at, say 27-30 kph. I haven't personally done that with this build but other than first hand experience the next best way to look at this is the awesome tool Justin Lemore and his crew at Grin cycles (thanks guys!) has created for everyone's use: http://www.ebikes.ca/tools/simulator.html

There are great instructions for working with the simulator, and I recommend playing with it if you get the chance. You first select the motor (thankfully there is a Cute Q100 with the 328 RPM fast wind in the list), then enter your battery characteristics and controller power limits. An important one for you here is to compare & contrast is the assumed battery voltage and it's impact on top speed.

They don't have the Q128 explicitly modeled but let's stick with the Q100 for now. Note that the throttle is set at 100% by default, to hit a lower target speed of 27 kph you need to adjust the slider.

Here are a couple screenshots where I attempted to match the bottle battery you are proposing to use with the Q100 @ 328 RPM. Note that to get a conservative estimate of power requirement (black "load line" curve) I left it set to the default drag coefficient of upright mountain bike. You will almost certainly have a lower drag coefficient, and require less power at a given speed, than this example as you will be on a road style bike. I've also set the human input to zero for worst case not pedaling at all.

First one is at 100% for max speed. You can see where I've circled the required motor power, and resulting power from the pack. This is running the system at maximum amps from the controller and you can really see the impact of the voltage "sag" under load from the bottle battery limiting the top speed to 43 kph (27 MPH). My lipos have less internal resistance and thus sag less so the motor sees a higher effective voltage under load which results in a higher top speed of 48+ kph (30+ MPH).

Since the Grin crew updated the motor heat modeling for some models (but not all, sadly not for the Q100) it does not show an explicit final winding temperature prediction. Running the Q100 at this power level for extended periods will result in overheating. When I say extended periods I am talking multiple miles continuously; bursts of this speed can be handled OK by the Q100. This is where the larger Q128 would give you more time at this higher load before it overheats. Maybe someone that has flogged a Q128 will weigh in with some real world anecdote on how long you can push these loads...
Q100 328 RPM 100% throttle 43 kph.jpg
Q100 328 RPM 100% throttle 43 kph.jpg (43.44 KiB) Viewed 3942 times

The next one up is the lower speed/throttle scenario you are describing, the late night "just get me home" mode (Been there!). You can see the loads resulting from the lower speed are significantly lower (just as Dogman was describing in this thread). This power level is well within the Cute's capacity, even the Q100, and shouldn't be a problem running at this speed.

Q100 328 RPM 51% throttle 28 kph.jpg
Q100 328 RPM 51% throttle 28 kph.jpg (43.34 KiB) Viewed 3942 times
#1 GT i-drive 5- 12s LiPo, yescom 48v1000w kit- stolen
#2 Kona Stinky Dee Lux-18s LiPo, MXUS 2806 DD, 12 fet from em3ev- retired
#3 Gary Fisher Hoo Koo E Koo-12s LiPo @ 10 Ahr, MXUS 2806 DD, 12 fet from em3ev- in use
#4 Specialized Crossroads-12s LiPo @ 10 Ahr, Bafang SWXH, 6 fet from em3ev- retired
#5 Foundry Harrow cyclocross-12s LiPo @ 5 Ahr, Cute Q100C 328RPM, 6 fet from em3ev- in use

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by molybdenum » Mar 19 2018 3:43am

I wouldn't do the 328RPM@36V Q100; at 48V, it's RPM would be 437 RPM since RPM is directly proportional to voltage. Although theoretical top speeds would be very high, you would need 1000+W at at least 20A (and big battery) to realize them. As you see in the sims provided by MonkeyWrench, to achieve 40 kph, you need to put in around 700 W (combined leg and motor). To achieve 50 kph, follow the black load line and you will see it requires well in excess of 1000W total power. 35 kph (where I spend most of my time) is achievable with just 400W total power. Unfortunately, due to wind resistance, power required rises exponentially with speed.

They do make a 201RPM@36V (268@48V) Q100c, which would top out at 40 kph and have much better hill climbing. This is akin to the Q128c motor I have but smaller. If your ride is relatively flat, and you enjoy long stretches without need to stop, the 260RPM@36V Q100H would spin at 346RPM given 48V would give higher top speed (provided the power) but is something I'd only recommend in 700c wheel to the strongest cyclists who will work hard, and then only in a road bike. Unfortunately, the H series motors accept a freewheel, but I'm told they are wider and have more copper; thus they should be able to tolerate more abuse. Now back to the Q128c, there are 201RPM@36V and 260RPM@36V versions, which would spin at 268 and 346 RPM, respectively.

I achieve my excellent range by limiting the max amps to 10 for a max 500W output, which I only max out on hills. Given the choice between Q100 and Q128 at the powers I use, both could certainly handle brief climbs with 500W@10A,48V (the Q128 could do it all day) and I doubt there would be a noticeable difference in hill climbing between the two at these power levels. You would only see benefits to the Q128 at higher power levels where the Q100 would either saturate and cease to provide more power with increasing amps, or it would overheat (high volts or amps).

I opted for the Q128 simply because bigger means more robust in the long term and for the extra 1 kg, if I eat a couple burgers, I'd be lugging that anyways - though I have to admit the Q100 is far stealthier. Note there's nothing stealthy about a frame triangle mounted bottle battery, which just screams ebike. Off topic but for a stealthier look, I'm tempted to put a brick battery + controller in a pannier for my next build and live with the slight reduction in handling from having an extra 4kg over the rear.

For my decision to go with the slower 201RPM@36V, my commute has maybe 100m elevation change but constant rolling hills and traffic lights every 100m. Add areas with backed up traffic that need slow negotiation. Add this with the fact that I need an extra 300-400W to achieve the higher top speed and the choice is made.

If you do go for the faster wind motor, I'd only mount it in a road bike with drops where you could tuck and actually realize 48 kph with 700-800W total power instead of >1000W. These are some things I didn't consider before, but you would more than likely need that bigger 13.4 Ah+ battery to provide a fast wind motor (like the 260RPM@36V model) with enough power to actually realize the gains in speed and still have enough range. To live with a 11.6Ah battery over a 30km commute (using 60%), I must keep my average motor wattage to 300W, and there's no way I'd be sustaining 400W+ leg power for the duration to take advantage of the faster motor.
2012 Kona Dew Deluxe, Q128C and 9spd cassette, S12S sinewave controller, 48V Panasonic battery

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by motomech » Mar 19 2018 5:23am

When Justin revised the sim. something happened to the modeling of the Q100 Cute 328. In the original sim, the 328 in a 26" wheel @ 45 to 48 Volts became power (Current) limited at around 22 to 23 mph. As an avg. cyclist, this was my experience exactly. But since the power line was pretty much a plateu, a strong cyclist could add w/ his legs, extending the top speed quite a bit, out to 26, 27 and even higher if we are to believe some of the reports here. One can add more Amps, in fact, this combo will have almost any controller trying to give it everything that it's worth, but /w little gain in top speed. I have never over-heated any version of a Q100 motor, but this combo would get my controller very hot. In fact, I flat melted the kit supplied bullet connectors on the phase wires. I know enough now to use 4 m/m bullets, but I also know the phase wires themselves will melt next.
For over a year, I ran my 2WD w/ two 328's and the synergy of the two motors helping to pull each other up into the "meat" of the power-band meant I could hit speeds around 29 mph. And while the "off-the-line" performance was good, the mid-range was lazy at best and I went to a pr. of 260H's. Together, they extended to the speed(over a single) a couple of mph to 25 mph, while being strong thru the entire performance range.
The way I see it, for the majority of riders, a mini in the mid-speed range (260 rpm @ 36 V) is the best all around motor. For those who desire a cassette (C) version, the Q128 328 rated @ 48 Volts is the way to go. This is effectively a mid-speed motor because if it was rated at 36 Volts, it would be 260 rpms. If I was to start a new build today, that's the motor I would use.
'11 Motobecane Fathom team, Bafang SWX02-11T, 14S (54V) LiPoly, PSW Power 9-FET 17A controller. Schwalbe Marathon's, 24 to 25 MPH.

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by motomech » Mar 19 2018 5:43am

My latest build started out as a Q100C 201 on 12S LiPoly(45.6V nom.) in a 26" wheel w/ a 17 Amp controller. Intended as an "assist bike", it certainly promoted pedaling as the top speed was around 18 mph and it took it's time to get there. Against my better judgement, I shunt mod'ed the controller to 23 Amps, increasing the acceleration from "zippy as a speeding glacier" to almost bisk, but top speed(no pedal) remained @ 18 mph. Not bad, but since I had the Lipoly bricks lying around, I went to 14S (53V nom.) and went back to a 17 Amp controller. Yes! This was what I was looking for, about 22 mph and fast enough to be entertaining.
100_0107.JPG
100_0107.JPG (89.08 KiB) Viewed 3917 times
BTW, there's 10,400 mAh of 14S LiPoly in the sm. frame bag and another 4,000 mAh in the home made bottle.
Going from 12S to 14S really hurt the range. W/ moderate pedaling on 12S, I could get almost 2 miles/Ah, on 14S 1 1/2 miles/Ah, at best.
'11 Motobecane Fathom team, Bafang SWX02-11T, 14S (54V) LiPoly, PSW Power 9-FET 17A controller. Schwalbe Marathon's, 24 to 25 MPH.

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by MonkeyWrench » Mar 19 2018 1:36pm

motomech wrote:
Mar 19 2018 5:23am
When Justin revised the sim. something happened to the modeling of the Q100 Cute 328. In the original sim, the 328 in a 26" wheel @ 45 to 48 Volts became power (Current) limited at around 22 to 23 mph. As an avg. cyclist, this was my experience exactly. But since the power line was pretty much a plateu, a strong cyclist could add w/ his legs, extending the top speed quite a bit, out to 26, 27 and even higher if we are to believe some of the reports here. One can add more Amps, in fact, this combo will have almost any controller trying to give it everything that it's worth, but /w little gain in top speed.
Hmm, that's interesting because I'm seeing much different behavior out of my Q100/6 FET Infineon style controller combo. It is fairly easily able to push me to about 28 mph throttle only. I'm not sure why you were seeing such different behavior. Do you recall what your amp limit was set to? Pretty sure I'm running about 18-20 amp limit.

I do agree that this combo puts the system in an amp-limited condition at the high speed 100% throttle condition, as seen on the sim. But, I haven't had an issue with overheating of controller or motor in normal riding.

Here are a couple of plots from Strava where I was first testing out the build (pretty level terrain):
Foundry Harrow Q100 testing.PNG
Foundry Harrow Q100 testing.PNG (18.47 KiB) Viewed 3895 times
Here is a closeup of a segment I know I wasn't pedaling on:
Foundry Harrow Q100 testing 2.PNG
Foundry Harrow Q100 testing 2.PNG (10.51 KiB) Viewed 3895 times
#1 GT i-drive 5- 12s LiPo, yescom 48v1000w kit- stolen
#2 Kona Stinky Dee Lux-18s LiPo, MXUS 2806 DD, 12 fet from em3ev- retired
#3 Gary Fisher Hoo Koo E Koo-12s LiPo @ 10 Ahr, MXUS 2806 DD, 12 fet from em3ev- in use
#4 Specialized Crossroads-12s LiPo @ 10 Ahr, Bafang SWXH, 6 fet from em3ev- retired
#5 Foundry Harrow cyclocross-12s LiPo @ 5 Ahr, Cute Q100C 328RPM, 6 fet from em3ev- in use

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by motomech » Mar 19 2018 4:09pm

I've used so many controllers over the years, it's hard to remember them all.
My original usage of the Q100 328(called the Cute 108 @ the time)was when they first came out, around 2009. Back then, there were no "H" or "C" versions and I'm pretty sure I was using KU63 6-FETS from BMS Battery, which are true 12 Amp controllers. It was these or the KU65's that I used in the 2WD bike and they probably were shunt modd'ed at some point to 17 Amps.
Then I used a very Hot Lyen infineon he set to 22 Amps, then the standard 20 Amp "Grineon", then the first Sine Wave SO6S from BMS Battery(too slooooow) and as recently as last year, I had a new Q100C (328), Black Akima on the bike pictured above, which has a 17 Amp 9-FET from ELIFEBIKE.
In all the combos, the top speed for a single Q100 328 (stand. or C) on 12S or 48V never varied, 22 to 23 mph.Every now and then someone comes along and they are getting 28 or 29 mph out of a single 2.0Kg Q100 and I wonder "how in the heck"? Rarified air? Oh well, these days I don't worry about it.
My tired old eyes can't read the faded graph you posted, are you sure those aren't Kph and not Mph?
'11 Motobecane Fathom team, Bafang SWX02-11T, 14S (54V) LiPoly, PSW Power 9-FET 17A controller. Schwalbe Marathon's, 24 to 25 MPH.

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by MonkeyWrench » Mar 19 2018 7:30pm

Yep those values are good ol MPH. FWIW I was riding "on the hoods" not "in the drops" for those tests, mostly because I can't reach my current throttle in the drops right now, and riding on the hoods is more of a default position.

That's very odd regarding the difference in speed. I wonder if its possible you were sent a slower wind accidentally? Stranger things have happened on orders out of China... but to have it happen multiple times is a stretch. You've certainly got plenty of variations with these little motors and experience with various controllers.

Tonight I'm going to measure the unladen sparrow RPM of the Q100C and compare to the Grin simulator.

Aha, I know what it must be! ...the bladed spokes :lol:
#1 GT i-drive 5- 12s LiPo, yescom 48v1000w kit- stolen
#2 Kona Stinky Dee Lux-18s LiPo, MXUS 2806 DD, 12 fet from em3ev- retired
#3 Gary Fisher Hoo Koo E Koo-12s LiPo @ 10 Ahr, MXUS 2806 DD, 12 fet from em3ev- in use
#4 Specialized Crossroads-12s LiPo @ 10 Ahr, Bafang SWXH, 6 fet from em3ev- retired
#5 Foundry Harrow cyclocross-12s LiPo @ 5 Ahr, Cute Q100C 328RPM, 6 fet from em3ev- in use

Commute ~32 mi roundtrip in Seattle

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Re: Lightweight/discrete Q128c commuter build on a road bike

Post by ModeratelyFastF » Mar 20 2018 7:16am

I have read all the replies with great interest (and checked out the simulator!) and now my head is well and truly spinning.

For the record, my commute is long, flat, and quiet - some days the only time my feet touch the ground are when I set off and when I arrive. Thus aside from my 4 hills, my average speed rarely drops significantly.

My current thoughts are to go with an EM3ev battery at 50v (aka 52v 14s) in a triangle frame bag https://em3ev.com/shop/em3ev-triangle-battery-bag/. I did want it to be discrete, and although a EM3ev triangle bag is hard to miss, it does pass for a luggage bag rather than scream ebike like a bottle battery.

Based on reports on these very forums the s12S controller and S-LCD3 combo from BMS Battery is fine with 14s viewtopic.php?t=82106.

The battery will probably be the 50v 17.5Ah triangle battery (inc triangle bag) with 862Wh at a weight of 4.3kg for $429USD https://em3ev.com/shop/50v-14s6p-small-triangle-pack/. This is only 300grams (10 ounces) heavier then the Bottle-09 battery I was originally looking at, but with much more energy. I will of course need an external controller, but it will fit in the triangle bag easily and I plan to vent the bag.

Then the last decision to make is which motor. Based on the above discussion the safe options seem to be:

48v q128c (328rpm) which would have an unloaded rpm of 340-350rpm at 52v, or
36v q128c (201rpm) which would have an unloaded rpm of 280-290rpm at 52v or
36v q100c (201rpm) which would have an unloaded rpm of 280-290rpm at 52v (a bit over ~40kph top speed)


I suspect in terms of long term reliability, top speed and robustness the q128c wins out. With 862Wh of power I think I will also be able to take better advantage of the faster wind on the q128c without overheating the motor. Now I just need to decide if I go for the 36v 201rpm wind or the 48v 328..

Any fatal flaws in my plan?

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