School ebike

[Cheddles]

Hi All,

I've read through a number of the forum threads here and have found the information to be a great blend of useful and inspirational (especially Keplar's super commuter). This is my first time posting For context, I'm a secondary school teacher in physics, maths and engineering. Before teaching I spent some years as an aeronatuical engineer so I'm not totally useless in practical matters but have never built an ebike before. Feedback on the following would be appreciated in case I'm heading in totally the wrong direction.

What I'd like to do is set up a smallish project for students to build a basic ebike that will serve as a testbed for a range of follow-on projects. If this works, I'd like the students to build additional bikes in a range of configurations to suit a range of rider size and purpose. The main requirements for the first bike are:

• robust
• simple to build
• flexible configuration
• low-cost (up to about $1000 total)
• disk brakes (so we can easily switch between different wheel sizes)
• able to take 700c road rims
• road-legal (200W output)

Obviously this is a little different to your average ebike requirements list as range doesn't really factor in for now. I'm notionally aiming for about 20-30km but it's not critical.

An initial list of parts that I'm considering is:

• Donor bike this cheapie from BigW
• Rear hub motor kit 700C version of this with controller and both throttles
• Batteries 3 or 4 of these LiFePO4 in series
• Cycle Analyst V3
• torque arm

This will hopefully give us a starting point that is easy enough for the students to build in the 8x100min sessions allocated. A couple of year 12 students will be helping out who have experience in building regular bikes but not ebikes. I expect that the final product will look extremely dodgy with lots of cable and cable ties around the place. This is OK as we will be trying a few different configurations once we get something working.

Thoughts and feedback on this?

Cheers,

Chris

 

[gogo]

If you want to use regeneration in your project, you'll want to consider using a direct drive motor instead of the freewheeling geared motor you listed.

 

[dogman dan]

Unless you open the controller to build in the plug, you'd CA v3 won't have all the features it comes with enabled. Speed limiting, amps limiting etc don't work with a CA stand alone.

Likely you can handle wiring the DP plug on to the controller though. But if you only want reliable wattage readouts and such, just get the CA V2, stand alone.

 

[docnjoj]

It has been done before by a schooteacher using a Schwinn trike and front hub motor. I can't remember his name but he is an active member on this board.
otherDoc

Mikefairbanks is his name.

 

[Cheddles]

Hi all,

Thanks for the feedback so far.

• No need for regen at this point so it's a trade-off we're prepared to take to avoid cogging. I selected that motor mainly on the strength of Keplar's experience with it on his Super Commuter as being robust enough to tolerate a range of higher power inputs if that's what we want later.
• The V3 is mainly to allow flexibility for later projects. Thanks for the info on plug incompatibility - I wasn't aware of it.
• Thanks for that - I'll look up Mikefairbanks and any threads discussing his trike project.
• Lego bricks? You've lost me here. The different rider sizes is simply to accommodate the large and small students we have at the school. The different configurations is for road/MTB, different wheel diameter, tyre widths, front and rear hub motors, different battery mounting locations, etc. The different purposes is about use of the bikes for experiments in different subjects (physics, human performance, etc.)

 

[dogman dan]

That was sure helpful K.

Sounds like much fun, gathering data always fun.

If you get the V3 CA, you can convert it to a stand alone for use with any controller for gathering the wattage data.

You have to add a speedo too, but I think you can get that added to a V3. Come to think of it, just ask the guys at grin. I bet they can just set you up with a CA V3 with speedo and a separate external shunt. I bet they can fix you up.

Actually, the parts are in the catalog now. Go Grin!

Shunt with DP plug.

http://www.ebikes.ca/shop/ebike-parts/ca-accessories/shunt-ca3.html

Adding this speedo sensor is easy, just solder two wires to the board. But maybe they'd do that for you if you ask.

http://www.ebikes.ca/shop/ebike-parts/ca-accessories/ca-speedo.html

And if you want to make a controller DP compatible, this part

http://www.ebikes.ca/shop/ebike-parts/ca-accessories/ca-6pinf.html

 

[chas58]

I'm not sure about the lego bricks route.

If you are going to use Zippy LiFePo4 bricks, how are you going to handle the duties that the BMS normally does without a BMS? Or will you add one?

Its just a lot simpler to use LiFePo4 pack with a built in BMS for an e-bike.

 

[mybike]

Kiriakos GR Are you seeing things? LEGO bricks LOL?
Its one your normall replys that don't make sence LOL

Yeee.. anyone reading this don't try to build a ebike with lego bricks its Dangerous!!!

 

[Dauntless]

Kiriakos GR Are you seeing things? LEGO bricks LOL?
Its one your normall replys that don't make sence LOL

Yeee.. anyone reading this don't try to build a ebike with lego bricks its Dangerous!!!

Ah, but Legos would love to see you try. In school. I think he just got a little too caught up in the Legos hype. http://education.lego.com/en-us/learn/middle-school/mindstorms-ev3/subject-focus

 

[Cheddles]

Wow - that's even more cynical than I get accused of being ...

Just to be clear here - we have budget to buy parts. The only thing I seek for free is advice. As a newbie, I would like to be sure that the parts we buy will actually work together - something that can take some experience with the different compatibility issues in cycling and electrical systems.

As for student ability, you underestimate the capability of our students (and I suspect students in your own country). My students are year 10-12 (age 15-18 years) and many have some experience building projects of similar complexity. The two students running the project first came to my attention when they designed (using CAD) and 3D-printed a rear derailleur hanger for their mountain bikes as they were concerned that the OEM aluminium ones were too strong to serve as a reliable mechanical weak link. They did this at age 15 with absolutely no staff assistance (they only spoke to me to get access to the 3D printers).

I hope this allays any concerns you have. If my anonymity worries you, please drop me a PM and I'll happily pass you my school contact details and you can verify however you like.

I still have no idea how this relates at all to Lego.

Cheers,

Chris

 

[Cheddles]

If you are going to use Zippy LiFePo4 bricks, how are you going to handle the duties that the BMS normally does without a BMS? Or will you add one?

Its just a lot simpler to use LiFePo4 pack with a built in BMS for an e-bike.

Hadn't considered on-board BMS so thanks for raising it. The plan was to use 1P packs to minimise balance issues with parallel chains and then charge each 4S pack separately on something like this charger to start off each ride with all cells balanced. On further reading, a BMS seems prudent once you get 12+ cells in series.

Any recommendations for a LiFePO4 pack with built-in BMS?

 

[dogman dan]

Pingbattery.com for a good bms equipped lifepo4 pack.

But I see no danger in using the "lego bricks" batteries as long as you are choosing the safer lifepo4 chemistry. Do have them wear gloves when connecting stuff, since a mistake can lead to burned fingers. Perhaps do that part yourself.

Definitely wouldn't bring the lithium cobalt "lipo" packs into the classroom.

 

[Cheddles]

Pingbattery.com for a good bms equipped lifepo4 pack.

But I see no danger in using the "lego bricks" batteries as long as you are choosing the safer lifepo4 chemistry. Do have them wear gloves when connecting stuff, since a mistake can lead to burned fingers. Perhaps do that part yourself.

Definitely wouldn't bring the lithium cobalt "lipo" packs into the classroom.

Thanks for that - I now understand the Lego bricks reference - I've never heard them called that before.

My preference is for LiFePO4 for safety and longevity reasons. We actually have a fairly active model aircraft program at school so quite a few LiPo batteries and experience using them safely (albeit usually much smaller than we are considering for this project).

I'll look at the plugs and configurations when we get the gear and ensure that students only use it when they physically can't plug things in dangerously incorrectly. Again, the model aircraft world has been dealing with high-powered battery safety for quite some time and have built some good approaches.

 

[Cheddles]

Pingbattery.com for a good bms equipped lifepo4 pack.

I just checked out their packs and they seem to have a minimum width of ~100mm so a bit wide to mount in the frame between the rider's legs :-(

Can anyone recommend a thinner form-factor pack (ideally less than 50mm thick)? Either that or a BMS that is able to work with the balancing leads from the Zippy Lego brick packs?

 

[teslanv]

Kiriakos GR Are you seeing things? LEGO bricks LOL?
Its one your normal replys that don't make sense LOL

Yeee.. anyone reading this don't try to build a ebike with lego bricks its Dangerous!!!

:lol:

I will try for a second time to make my point.
I do not believe that there is a school in our planet in which young boys is capable to construct their own bicycles as to were mechanics, just so to test them with a spinning hub.
What I am sensing is some one totally anonymous who fishing for gaining free ebike parts donation.
Which is the dream of anyone who has no wallet so to buy a KIT.

If I am wrong, I could be only accused that I am always on-guard about believing any story which getting posted at ES.

Kiriakos,
Do you not have trade schools in your country?
I think you underestimate the capability of the younger generation. These are the kinds of projects that actually pique their interest and make them want to be electrical /mechanical engineers. If I had only been introduced to such a project in high school, what a different career I may have had!

Good luck with your project, Cheddles.

 

[999zip999]

Kiriakas is trying to tell us what a great E.E. he is and would like the world to know again. Sorry for that.
I do believe you are doing a school project. Good luck.
A good battery is the heart of an ebike. So put the money there. Ping packs will work well in the triangle. Make a battery out of two cardboard shoe boxes and duct tape for size before buying. Make it a little wider and longer to be sure.

 

[Cheddles]

Back again.

Rather than a full BMS, would there be any particular problem using a cheap cell monitor like this one? For the price, we could put one on each 4S pack and stop when any of them buzz. This would allow modularity of the batteries (good for replacing one fried one and adding extras if we want to overvolt in the future).

For the sparking/gloves mentioned by dogman dan, would Anderson pole plugs be a suitable solution? We can rig those up relatively easily to physically preclude incorrect attachment and they seem to have a decent shroud to protect from sparking.

Cheers,

Chris

 

[DAND214]

I have read this a few times but still confused.
You want to use a 36v motor kit and 4 x 4s LiFePo4 battery packs to make a battery for the bike. You need 3 of the 4 (36v) to get the kit running. Or are you planning on running 48v?

From previous post here those packs are not what they are listed as. The Ah and C rate is way less than they list. As others have said, the most important thing is the battery. A 100mm pack will fit between the legs and some cranks are that wide at the pedals. There are many bottle mount packs out there that would work for you. With the 4 bricks you listed you need the charger you listed and a power supply. Most Plug And Play batteries come with the charger. Something like this http://em3ev.com/store/index.php?route=product/product&path=35&product_id=160
There are other suppliers but this is the one that comes to mind.

Good luck with that great school project. Oh I almost forgot, YES the kids are capable of such a project 15/18 is by then I was rebuilding car engines. The new generations are either gear heads or electronic nuts, so your gonna have a great time.

Dan

 

[Drunkskunk]

Anderson power poles aren't the best option, as there is no Male/Female connector. So it's possible for some kid to attach one battery to another. XT60 connectors have a male/Female connector, and can't be reversed or interconnected wrong. Hobbyking and most hobby shops sell them.

There are also EC5, which I use, EC3, and Deans, which I used to use. The importance thing to have is a dedicated Male and Female connector that can't be reversed. That should help avoid students getting Kentucky Fried Fingers.

Those monitors look good. For a school project, that is probably much better than a BMS. It gives the students a hands on experience with the importance of balanced cells.

The battery packs you chose are great for a class room. They have been shown to be unsatisfactory for actual ebikes that get used every day, but for what you're trying to do, they're probably better than some generic off the shelf pack in terms of engaging the students with the project. From my perspective, it's easier to understand "These are batteries. If we put some of these together, the bike will go. This is how we monitor the cells, and this is how we balance the cells, and this is how we charge the cells" rather than a battery pack with built in BMS "This box contains a battery. Trust me. It makes the bike go."

This project sounds awesome. I hope you'll continue to post on the project so we can follow it's progress.

 

[999zip999]

Em3ev and Ping sale ebike batteries. A plug and play battery might be best. Ping has a signalab bms with leds for each channel so you can watch balancing and great support. Are going with 48v or 36v how many watt controller or amp draw. We need that to for battery choice.
As far as spark a precharge resistor will fix that.

 

[agniusm]

I like the idea of starting doing it with students of that age. Good job.
If you need narrow battery those packs you listed in first post are ok, you just need to connect a bms which is simple. There are bms'ses that do not cost that much. Pick one with suitable output current here: http://www.bestechpower.com/384v12spcmbmspcbforlifepo4batterypack/ and then its a matter of soldering controller wire, battery wire and charger wire. Also swapping jst connectors of the lego bricks. All the info is here and guys will help.
Note that there is 20A bms HCX-D245 which is 55mm wide, almost same width as those lfp bricks. Would make a nice small pack.

 

[Cheddles]

Thanks again all - I love the helpfulness of this place

Drunkskunk is dead right - my preference is for as little "black box magic" as possible. Once the students find the exposed way boring then they can explore more integrated/automated options. Until then, I'm happy for them to tussle with tedium and even break a few components (as long as they stay safe and the parts are relatively cheap).

Anderson powerpoles are universal but can be ganged together into configurations that can only be plugged in to a matched set of plugs. XT60s are also good and would be plenty to sustain the required current for our system (60A at 36V is about 2kW - far more power than we will likely draw on 36V)

The plan is to start with 3x12V packs to run everything at the labelled 36V but to leave open the option of running at a higher voltage later on if we want to explore that path. 48V seems like a reasonable first effort at overvolting. Buying a single 36V power pack locks us into a single voltage. Keplar indicated sustained success running that motor at ~83V so there seems to be plenty of headroom to play.