Newb with Question on Bottle Battery with BPM2

[MastaKebob]

Looking to build my first ebike. Been lurking for a while and think I got the basics. Hoping to get some guidance/validation before purchasing.

Background Info:
Desired max speed on level ground: 20mph on level ground with light pedaling.
Desired range: minimum of 5 miles at 18mph (I live in downtown DC, I plan on using this for 1.5 mile 1way commutes and 2 mile 1-way trips to the store).
Wheel size: 700c
Brakes: Cheapo Caliper brakes (will probably upgrade to dual pivot calipers during conversion)
Rider weight: 190lbs
Terrain: Mostly flat but a few short hills (going up a hilly block or up a parking garage ramp).
Ride Profile: Lots of starts and stops, mostly flat with minimal potholes. I usually get a block or 2 before having to come to a stop. I'm OK sacrificing top speed for speed off of the line and hill climbing ability. 99.9% of rides are on pavement.
Budget: $750
Skill level: Computer Engineer with some wiring and bike maintenance experience. Able to work a zip tie and wrench. Have an LBS on speed dial who can build and true wheels if necessary.

Donor bike:
BikesDirect.com Motobecane Bistro 7v: http://www.bikesdirect.com/products/motobecane/bistro-dlx-7v-city-bikes.htm

Anticipated purchases:
Motor Kit: 48v500w BPM2 kit (available from a variety of vendors, but probably either https://bmsbattery.com/ebike-kit/348-bafang-bpm2-48v500w-rear-driving-bike-conversion-kit-ebike-kit.html or http://www.elifebike.com/peng/iview.asp?KeyID=dtpic-2012-7U-CJNQ.05DJS)
Battery + Controller: 48v11.6ah Panasonic bottle pack with Controller from BMSBattery (https://bmsbattery.com/ebike-battery/680-48v116ah-bottle-09-panasonic-battery-pack-battery.html). Note that it comes with a 20A sine wave controller.
Torque Arms: 2 Rear torque arms to shore up the Al drop outs.

Questions:
1) Is the donor bike capable of safely handling this upgrade?
2) Battery + Controller: I've read (older) posts that don't recommend bottle batteries because of 'voltage sag' due to low C ratings. This particular bottle appears to have sufficient V's, C's, and AH's to drive a 48v500w BPM2. Is this a correct statement? If not, why not? How much performance hit will I take with this battery/controller over a Ping 48v10ah brick?
3) With the battery having a controller built in, can I bin the controller that comes with the Motor kit?
4) How difficult is it to swap out displays/throttles at a later point if I'm unsatisfied with the ones that come in the kit? Are they standardized connection-wise that I could plug and play a new one?
5) What vital thing am I missing?

Thanks in advance! Even if no one responds, this forum has been a huge help already.

 

[motomech]

Only one thing, too much motor. Too much motor for your needs, too much motor for your bike and too much motor for the bottle battery.
Most of the minis will handle 20 Amps, weight half of the BPM and be less of a risk on what appear to be rather fragile drop-outs.
for a frt. mount, the Q100H "Cute" 260 wind is the hot performer for it's size and on a 36V batt. will do 19 to 20 mph and suprise you with it's git off the line.
A 201 wind might be better for the 700cc wheel, it's borderline.
For the rear, the CST is the way to go("If you like your cassette, you can keep your cassette"). It's only available as a 201 wind, so you might see 18 mph.
20A might be a little much for the CST, but maybe not(I suspect D8veh might way in on this).
Order both the SLCD-1 and SLCD-displays, they are cheap enough. But as an engineer, you might like the SLCD-3(Read the downloads at the BMS B. site.
You haven't described big enough hills to warrant big motor/big batt. Minis get overwhelmed by hills rather quickly, but for all but the steepest SF type hills, they can handle hills of only 2 to 3 blocks. Just get a run at it and add with your legs.
Oh, and a mini will save you serious $$$.

 

[d8veh]

The 48v 09 bottle battery with Panasonic cells and 20A sinewave control is an excellent package. You can add a Bafang BPM, Bafang CST or a Q128 to that to get more power than what you need. The BPM and CST come in 260 rpm version, so no problem. The 201 rpm Q128 can just reach 20mph with a fully charged battery, or you can run a 36v one at 48v to get the equivalent of 260 rpm.

The Q100H should be OK too, but I'd go down to 36v. I'm not too sure whether the extra power from 48v would be too high in stop/start type riding. IMHO, the Q128 would be the best motor. It only adds 1kg to the Q100H option. At 48v, it has serious torque for steep hills in case you ever need it. The LCD allows you to turn the power down if you feel you want to contribute more pedal effort. Make sure you fit a pedal sensor to get the most out of the system.

You don't have to buy the whole kit with the wheel. If you look through their listings you can get the motor wheel on its own. The battery kit has everything else, including LCD, throttle, PAS, ebrakes and cables. You won't be dissatisfied with anything in the kit, so no need to swap anything. You will also need a 7-speed DNP freewheel with 11T top gear, otherwise your pedalling will be too frantic.

You need to get, additionally, their spoke key and a pair of torque arms.

Your bike looks perfect for that kit.

 

[MastaKebob]

Pardon my ignorance, but why a Q128 over a BPM2? I can't find much info on the Q128 and the BPM2 seems to be a popular option on this forum. And the Q128 is only ~$20 cheaper than the BPM2.
Also, what's the difference between a Q128 and a Q128h?

 

[MastaKebob]

Also, you recommend a pedal sensor. Can you have a pedal sensor while using a throttle? What benefit does a pedal sensor provide a throttle?

 

[d8veh]

The original Q128 was a bit gutless, but the newer Q128H has very good torque. I would say that it has the same torque as a BPM. I think that you will be reading a lot more about it in the future because it really is a good motor just like the Q100H, but bigger, stronger and more powerful. It's smoother and quieter than a BPM because the rotor runs faster. It's also lighter and stealthier. The Q100H has stood up really well to all the abuse ES members have thrown at it, so I would expect the Q128H to be even more robust.

They only come in 201 rpm, which is a bit slow for some, but you can get 260 rpm by using the 36v one at 48v.

The throttle takes precedence over the pedal sensor, so you use the PAS for normal riding, and, when you need instant more power, you can use the throttle any time. You will hardly want to use the throttle when you have this type of PAS system. It's so much more comvenient.

 

[MastaKebob]

Great answer, thanks! So a 36v q128h will be able to handle a 48v battery and 20a controller without issues?

And that's neat that you can use pedal assist and a throttle at the same time.

 

[d8veh]

It won't do any harm to run the 36v one at 48v. It's equaĺy as strong. The only difference will be the speed. They both have the same power rating.

 

[MastaKebob]

To follow up, I ordered the q128h (36v 201rpm) and the Panasonic bottle battery last night. https://bmsbattery.com/ebike-conversion-kit/644-q128h-36v800w-rear-driving-e-bike-motor-wheel-conversion-kit.html and https://bmsbattery.com/ebike-battery/680-48v116ah-bottle-09-panasonic-battery-pack-battery.html.

I'll update as things progress.

 

[d8veh]

Please let us know how it goes. I'm particularly interested in the speed.