Considering starting my first build - need advice

Apologies in advance for the lengthy question and details.

I have been commuting to work on a cheap Ancheer since mid-April and have had to overcome a lot of problems. This is the model I got, though it was through a different vendor:
https://www.amazon.com/ANCHEER-Electric-Mountain-Removable-Lithium-Ion/dp/B07HJXY45D

Apart from an assortment of mechanical problems, I had to replace the PAS sensor that hugs the BB spindle with something aftermarket. This involved pulling apart the connector and re-arranging the pins to get it to work with my controller. Also, I recently encountered some major voltage sag with that 36v 8ah battery and replaced with a 48v 10ah pack (the controller was labeled as 36v/48v). Beyond that, I don't have a lot of experience with e-bikes. I am an IT guy, but not well-versed in electronics. These first dives into the electrical side of the bike, along with other successes in learning general maintenance of the bike have me wondering if I could make a better commuter.

I am in the Roanoke Valley in VA, so there are small mountains nearby and lots of hills. I do not have an accurate read on the grades but would say my commute is a mix of 2% - 18+% along my 5.7 mile journey. My work situation has me bouncing between buildings .5 - 2 miles apart on occasion, so I cannot be constantly changing clothes during the hot summer. The bike I have is doing okay, but for part of my commute, the bike lane along a 35MPH (traffic moves at 40) roadway ends, and for about a quarter of a mile I have no shoulder and have to cross over into a left lane as the right-most lane becomes a right-turn-only lane. For that quarter of a mile, it is mostly flat, probably no more than about 5% grade, and I would like the option of cranking out 40 - 45 MPH if I were to need it to safely get over.

I think I would like to stay between 20 - 30 MPH for most of the trips, but might also take advantage of some torque overhead for some of these hills (18+MPH with pedaling). I also acknowledge that I might also enjoy a little burst of 40+ every now and then once I get a taste of it. I'm not looking to put plates on this build or register it as a moped, so I would prefer to not draw a lot of attention from the friendly, bored police officers around here.

This deal popped up on Facebook and I negotiated the price down a bit and pulled the trigger:
https://www.facebook.com/marketplace/item/1935836666718725?surface=product_details

I do not know the year, but the bike feels pretty sturdy. It has a better drivetrain than my Ancheer - it's got a Shimano Alivio groupset and Shimano Disc Brakes on front and rear.

My thoughts were that I needed something in the 1500W to 3000W range in order to reach the aforementioned speed goals. Some discussion here around the LeafBike 1500w hub motor makes me think it would be the best motor for the job. I'm not sure their kit will cut it though.
http://www.leafbike.com/products/diy-bike-conversion-kit/26-inch-electric-hub-motor-kit/newest-26-inch-48v-1500w-rear-hub-motor-bike-conversion-kit-987.html

I am eyeballing 2 batteries:
https://www.aliexpress.com/item/Free-Battery-Bag-52V-30AH-E-Bike-Lithium-Battery-Pack-2000W-52V-Triangle-Battery-Use-Samsung/32848117615.html?spm=a2g0s.8937460.0.0.2d0a2e0erM4sf4

https://www.aliexpress.com/item/72V-battery-72V-3000W-use-Panasonic-cell-electric-bike-Battery-72V-20AH-Triangle-lithium-battery-with/32835895306.html?spm=a2g0s.8937460.0.0.2d0a2e0erM4sf4

I think the first one could be paired with the kit from LeafBike and it would give me a lot of range and some decent power, but I'm guessing it would top out at around 35 MPH. I asked the folks at LeafBike if the controller in that kit can accommodate 72v but they said it will not. They directed me to a 72v controller they offer, but I'm almost thinking a 72v sine wave controller would make better sense in that price range.

My concerns are that the frame is probably aluminum and not steel and might not be suited for 40 MPH. At the least, I'm sure torque arms are necessary. Should I avoid trying to go that powerful on this bike?

Is there a particular controller that would be better given the options I looked at? Do any of you have better recommendations? I have been looking at some options on EM3EV, and things like this on AliExpress:
https://www.aliexpress.com/item/Kelly-Sinewave-E-bike-Controller-KLS7218S-24V-72V-200A-SINUSOIDAL-Controller-for-1000W-1500W-Brushless-Motor/32809128486.html?spm=a2g0s.8937460.0.0.2d0a2e0erM4sf4

I have no experience with programmable controllers. I am aware that the battery BMS should be able to output more amps than the controller will try to draw. I'm a bit skittish of Lipo chemistry, so I don't really see how I could get a battery that could accommodate the amp output of some of those controllers. Can I just simply set a limit on the controller to not exceed 50a and go ahead an pair with one of those 18650 triangle packs?

Read your post quickly but as I understand it you want to go fast.
So
You will need
E-Bike Specific Frame from ...
Em3ev.com ( China )
Vector E-Bike ( Germany/Ukraine )
Stealth bikes ( Australia )
Qulbix ( Slovenia )

Then 3,000 watt or higher power motor .

Then a Very Large Battery Pack.
for the speeds you want, I would use a custom made pack . Tell the battery maker the volts and amps , speed and distance you desire.

pulsar said:

The bike I have is doing okay, but for part of my commute, the bike lane along a 35MPH (traffic moves at 40) roadway ends, and for about a quarter of a mile I have no shoulder and have to cross over into a left lane as the right-most lane becomes a right-turn-only lane. For that quarter of a mile, it is mostly flat, probably no more than about 5% grade, and I would like the option of cranking out 40 - 45 MPH if I were to need it to safely get over.

Click to expand...

I dunno. You want to burst to around 45 mph (which is close to the max speed for your bike that probably wasn't designed with this kind of speed in mind and yer now going 15 mph beyond the legal speed limit for an ebike in VA.), cross over a lane in traffic, and then climb on the brakes to slow or stop for a left hand turn. If it were me, and traffic wouldn't allow me to change lanes safely at my 25-30 mph speeds, I'd just ride through, dismount at the corner, and then cross at the crosswalk - either on foot or on the bike. Also, on that problematic 1/4 mile, consider using the sidewalk if there is one that has low or generally no pedestrian traffic and has few or no driveways.

Yeah, there's got to be a better way to get where you're going, cause this is going to catch up with you pretty fast. Anyway, just a practical point here, I believe the key parameter here might be max current. I suppose that if they ship a motor that can handle 40A at 48V, then the motor can handle that - and you want a battery that can sustain that discharge rate. The 52V battery you link to says "maximum continuous discharge current: 30A", so it's a little short there. I don't have a lot of practical experience with this stuff. I suspect if you inquired about it, they'd tell you not to worry, you aren't going to ride the whole way at 40A are you? and it can spike up to 90A. Meanwhile the motor may not be able to take 40A after all, so this eventuality won't even come up. So ... I'd look for something with a higher discharge rate if you want to push that motor, but if it doesn't work out it may not be a big issue.

wturber said:

I dunno. You want to burst to around 45 mph (which is close to the max speed for your bike that probably wasn't designed with this kind of speed in mind and yer now going 15 mph beyond the legal speed limit for an ebike in VA.), cross over a lane in traffic, and then climb on the brakes to slow or stop for a left hand turn. If it were me, and traffic wouldn't allow me to change lanes safely at my 25-30 mph speeds, I'd just ride through, dismount at the corner, and then cross at the crosswalk - either on foot or on the bike. Also, on that problematic 1/4 mile, consider using the sidewalk if there is one that has low or generally no pedestrian traffic and has few or no driveways.

Click to expand...

You may be right. Perhaps 45 mph is excessive.

Before that particular problem stretch the road is 2-lane with a safe left turn lane. When the bike lane ends, there is no shoulder and no sidewalks at all through there. When it breaks out into 2 lanes going toward work, the right lane is a right-turn only that turns onto a long, steep bridge that's 4 lanes and 45 mph with a Sheetz at the corner. Lots of cars going in and out of there, so I would rather not got that way.

I have to cross into the left lane just to stay straight and avoid all that Sheetz mess, and there is no crosswalk through the intersection. Shortly before the light, a third lane forms that is a left turn only.

There is only one other viable route, but there is significant steep hill climbing - probably 30 degrees+ for a couple miles. They are 2 lane roads, and there is no shoulder or sidewalk, and lots of folliage and viney ivy/VA Creeper along the side of the road way for critters to pop out unexpectedly.

My town has railroad tracks and a river running through it that screws up the road layouts and there are not a lot of ways to get where you are going, unfortunately.

What about 38 - 40 mph as a top speed? Would that be do-able on that frame?

I just built a bike based on a Trek that is similar to that Specialized.

Its a 1500W motor, 22A (45A peak) controller and a 52V 24Ah battery.

Max speed I have been is 58kph (36mph) and the bike seemed to handle it ok, although I wouldn't want to go any faster than that on it and I wouldn't want to cruise at that speed. It would be doable for a short stretch of road but I wouldn't make a habit of it. The frame/bakes/tyres just aren't designed for those speeds.

40kph (25mph) feels much better on this setup.

Also, the faster speeds will consume the battery a lot faster. You get much better mileage under 25mph.

Looks like a car trip to me. You need to pull a hairy merge maneuver at 45mph, you want to travel in hot weather in street clothes ... You could make the 45mph part happen with a motorcycle, but a bicycle isn't really a sane way to do that, nor 40mph. And then sane motorcyclist typically will suit up in protective clothing - helmet, gloves, armored jacket and pants, boots with ankle armor and no laces. Many scooter riders don't bother, but then they're not riding 45mph either.