BMS Rear Rack Battery Anyone tried it?

Hello All,

Im considering a few options for a bike build for my wife and im considering buying her a different bike with a steel front fork and could then go with a Q100 front drive. To balance out the weight and keep with the look of the bike Im considering buying a rear rack mounted battery. Frame downtube also curved so would be difficult to have a dolphin type pack.

Anyhow this is the rack I am considering: https://bmsbattery.com/ebike-battery/771-36v125ah-case-02-18650-battery-pack-battery.html



Motor would be a 36V Q100 front drive.

Unfortunatley this rack system is not available in 48V with an integrated controller.. Perhaps no room or their desire to keep it under the 350W instal limit.

Thoughts?

I've converted a couple of bikes with one of those battery/controller systems. Nothing to report except they worked and did what they were supposed to.

The battery has a compartment at the front that houses a standard controller. Personally, I prefer the non-moulded connectors because it's easier to test if you get any problems. If you want 48v, their 48v rack batteries have the empty compartment and you can get the 17A sine wave controller and sensors from PSWpower.com.

Mine weighed 10lbs and putting that weight up above the rear wheel did not do the handling any favors.

It made less of a difference on a touring style bike that was designed to carry a load, less friendly to more racy frames. I've moved the battery to the main triangle, and loosing some weight (Keeping the weighty low also helped when using a rear rack).

chas58 said:

Mine weighed 10lbs and putting that weight up above the rear wheel did not do the handling any favors.

It made less of a difference on a touring style bike that was designed to carry a load, less friendly to more racy frames. I've moved the battery to the main triangle, and loosing some weight (Keeping the weighty low also helped when using a rear rack).

Click to expand...

Wow 10lbs seems high. My wife doesnot need snappy handling. Bike im looking to electrify is aupright dutch type bike. Likely gonna be a Pure City 3 or 8 speed. This has a steel front fork so figured a Q100h on the front and this rack bettery on the back. The swoopy downtube make mounting a case battery in tnis frame is tough. Wife is French so bike must be pretty and i want to be as minimal as possible in outward experience that its electric and also is as light as possible for her. She needs tbe upright riding posture since her current hybrid hurts her back a bit since its a bit forward of a posture.
Marc

My BBS02 beater with rack battery (48V). Its curved downtube didn't look too friendly for a Dolphin battery. I don't ride it in a manner that needs handling, so I've not noticed any tradeoff. Last summer, when we went riding in Colorado (paved bike paths) I added saddlebags with a spare Luna Mini, and a spare Dolphin for my wife's ebike, to alleviate range anziety. Add some tools, water bottle and I had 25 pounds in addition to the battery. Never felt it.

My BBS02 beater with rack battery.
.
If you go with front wheel drive, and the integrated controller, I suggest adding the 9 pin motor extension cable to your Q100H order. In my opinion, the round connectors, if you purchase the associated brake lever/throttle/LCD will facilitate a cleaner look for the wiring.

I have the 48V15Ah Li-Ion battery with rack on the back of my Schwinn cruiser. The battery itself is almost 15 lbs and I think more than half of the weight is mounted behind the rear wheel centerline, and it definitely affects handling. There is far more weight on the back wheel with me, the hub motor, and the battery than on the front making the bike a little squirrely... but maybe only really noticeable at 20+ MPH (most of my commute at 30+ MPH is pretty nerve-wracking). Should be fine at reasonable speeds with a smaller battery.

I mounted the controller and a tube with the mess of wires in it on the stays that connect the rack to the bike, there's some room in there to work with.

Overall I think it's pretty convenient and let's you still use the rack for other purposes. I don't think you'll have any problem with it.

jhendrickson said:

I have the 48V15Ah Li-Ion battery with rack on the back of my Schwinn cruiser. The battery itself is almost 15 lbs and I think more than half of the weight is mounted behind the rear wheel centerline, and it definitely affects handling. There is far more weight on the back wheel with me, the hub motor, and the battery than on the front making the bike a little squirrely... but maybe only really noticeable at 20+ MPH (most of my commute at 30+ MPH is pretty nerve-wracking). Should be fine at reasonable speeds with a smaller battery.

I mounted the controller and a tube with the mess of wires in it on the stays that connect the rack to the bike, there's some room in there to work with.

Overall I think it's pretty convenient and let's you still use the rack for other purposes. I don't think you'll have any problem with it.

Click to expand...

Thanks for the reply. Do you have a pic?

addicted2climbing said:

chas58 said:

Mine weighed 10lbs and putting that weight up above the rear wheel did not do the handling any favors.

It made less of a difference on a touring style bike that was designed to carry a load, less friendly to more racy frames. I've moved the battery to the main triangle, and loosing some weight (Keeping the weighty low also helped when using a rear rack).

Click to expand...

Wow 10lbs seems high. My wife doesnot need snappy handling. Bike im looking to electrify is aupright dutch type bike. Likely gonna be a Pure City 3 or 8 speed. This has a steel front fork so figured a Q100h on the front and this rack bettery on the back. The swoopy downtube make mounting a case battery in tnis frame is tough. Wife is French so bike must be pretty and i want to be as minimal as possible in outward experience that its electric and also is as light as possible for her. She needs tbe upright riding posture since her current hybrid hurts her back a bit since its a bit forward of a posture.
Marc

Click to expand...

That setup should be fine with a rack (assuming you aren't going high speed). My battery was a LiFePo (36v10ah), which are relatively heavy, but it did weigh a bit more than listed on the site. Newer batteries tend to be a little more energy dense and lighter. Attaching the top of the rack as far forward (close to the seat post) as possible helped a little - keeping its center of gravity in front of the rear axle.

chas58 said:

addicted2climbing said:

chas58 said:

Mine weighed 10lbs and putting that weight up above the rear wheel did not do the handling any favors.

It made less of a difference on a touring style bike that was designed to carry a load, less friendly to more racy frames. I've moved the battery to the main triangle, and loosing some weight (Keeping the weighty low also helped when using a rear rack).

Click to expand...

Wow 10lbs seems high. My wife doesnot need snappy handling. Bike im looking to electrify is aupright dutch type bike. Likely gonna be a Pure City 3 or 8 speed. This has a steel front fork so figured a Q100h on the front and this rack bettery on the back. The swoopy downtube make mounting a case battery in tnis frame is tough. Wife is French so bike must be pretty and i want to be as minimal as possible in outward experience that its electric and also is as light as possible for her. She needs tbe upright riding posture since her current hybrid hurts her back a bit since its a bit forward of a posture.
Marc

Click to expand...

That setup should be fine with a rack (assuming you aren't going high speed). My battery was a LiFePo (36v10ah), which are relatively heavy, but it did weigh a bit more than listed on the site. Newer batteries tend to be a little more energy dense and lighter. Attaching the top of the rack as far forward (close to the seat post) as possible helped a little - keeping its center of gravity in front of the rear axle.

Click to expand...

Hey Chas,

I chatted with BMS last night and found out that the battery combo with rack is quite heavy but I think its doable. Battery is 3.9KG and rack is between 1 and 1.5kg.. Motor 2.1kg...so its close to a 17lb addition in weight. I think my Q128 setup with a larger Voltage and capacity battery was less than this. But im pretty sure she will hardly ever go over 15mph. I just need to see if the bike I plan to use has 36 spokes or not to match with the Q100H. Also is 12mm a common size for a front fork dropout? Need to check that on bike as well.

If the Priority Classic Plus bike did not have a rear coaster brake I'd go for that since its only 26lbs as opposed to 32lbs for the bike I am considering.

Thanks for all the advice so far everyone

Marc

If you really like that bike, and if the bike is equipped for it, maybe consider getting that and adding some simple sidepull brakes (with good brake pads). If you can add a motor, you can certainly add different brakes.

The axles take 12mm nuts, but they are squared off, as you will recall, and what remains is 10mm. I believe that's your standard drop out size. You might find that the U-cut in your front fork needs to be filed down a few mm deeper (not wider) to have the full 12mm fit better. You need good torque arms for safety.

The Q100 is indeed 4.8 pounds. I've weighed mine. I bought a custom 10S-3P battery and it supports 30 miles of riding. Probably around 3 pounds and fits in a seat bag.

docw009 said:

The Q100 is indeed 4.8 pounds. I've weighed mine. I bought a custom 10S-3P battery and it supports 30 miles of riding. Probably around 3 pounds and fits in a seat bag.

Click to expand...

Me too, as soon as I could get a 350watt-hours in a 10s3p (about 2 years ago, finally!). My battery is lighter than my motor!

That sounds about right, weight wise.

The weight of the motor (on my rear wheel) never bothered me as far as handling went.

I think you'll be OK at those speeds on a bike like yours. If you want the bike to be more agile its not the best place. But at 15mph on a dutch style bike it should be OK. That style is designed to carry weight on the racks.

Hello All,

I have been a bit preoccupied with work to get this build going. I spent the weekend test riding bikes for my wife. She is 6'1" and only 3" shorter than me so I figured I am close enough. Downside is most women specific bikes end at 5'10" but many are fine for a bit taller. I tried just about every Dutch geometry type city bike I could find: Pure City, Public, Electra, Raleigh & Linus. I also tried a few Mixte types as well. The Mixte would be perfect since my wife is French but of the ones I found they felt a bit small. Public has a nice one but could not find one to try. Also Linus has one in a Large but can only find Medium locally. Price is also an issue and I found the Pure City for $249 and at one bike shop I found a public C7 and the guy will let it go for $275 out the door. I am leaning toward the Public C7 since its red, rode nice and has a color matched rack. I hated how the Linus Dutchi felt. If money were not an issue I'd likely buy the Public Mixte. Anyhow, Below I have a few pics of the bikes with some simple configurations for the battery. I imported the jpegs into Solidworks, Scaled them until the wheel were 622mm and then sketched a simple battery and Q100. I decided against the rack integrated battery and will use a shark pack instead. One reason is I can use the shark pack on my mtn bike when I convert it in the future.

Public C7:
This bike has a rear derailer and with that it gives me options to put the motor on the front or rear. The image below does not have the rack but the bike I can buy does. I was thinking to mount the battery on the rack and then either hide it behind the cassette or put it on the front but it will be more noticeable. I'm on the fence with either configuration. On the front shares the weight front to rear, but this setup will be light and if the motor is on the back only the battery will be seen and if I add panniers I may be able to hide battery. Or place it in a basket on the back. Bike cost $275, BMS $585 for a total of $860



Public M7:
This bike has a nexus rear hub so Q100 would go on the front. The frame has room for the battery. as I said if money were not an issue Id go this route for sure. Bike cost is $765 than the items from BMS are $585 for a total of $1350



I also really liked the Electra loft but the curve of the frame would not allow the battery to fit inside it. I would choose the Public over this if I were going to buy a more expensive bike.

Last question in regards the the items from BMS. When I converted my bike I bought a Q128Cst 201rpm at 36V and a 52V battery and 48V controller. Dolphin case setup with waterproof wiring. I did this to overvolt the Q128 to get closer to 260RPM. I see that the Q100 is available in a 260 RPM version so unsure if I should just stick to a native 36V setup on her bike. Or buy the Q100 in 201V and buy the 48V pack and controller. I'd likely prefer 48V if I wanted to use her pack on a mountainbike, but my first priority would be what is best for this build. If I can re purpose the pack I will but its not needed. My mtn bike may not even be convertible as there is not much room in the triangle anyhow. So my question is what are the pros and cons of each motor setup mentioned above.

Thanks again for all the help everyone..