/diy/ E-Bike

>>1208064

Built three and a half of them. All for lulz, mostly, but one I use regularly for my commute. like $1.50 in gas to take the car, measured a round-trip's worth of electric for the bike at just over $0.05.


Anyway...been thinking about re-building it at some point for a couple specific reasons.

Hub motors are good and stealthy (especially a smaller, geared hub), but I'd really like to use the gears, for performance reasons.

I built a custom pack to fit the frame of this bike, and it's a little larger than it needs to be for a round-trip commute. I'd like it to be a _lot_ larger than it needs to be. I have another pack's worth of cells to use, and it's always good to have more battery than you need. If not for the capacity for out-of-the-way meandering, then for the reduced load on the pack and the increased longevity that offers.

Current-based throttle. The standard ebike throttles control the duty cycle of the controller, effectively varying voltage at the motor. This is kind of crap, because it means the throttle literally does nothing if it's pushed to a point lower than would be representative of the speed you're going. Depending on the characteristics of your motor, you may hit current limit only slightly above that point. The net effect of this is that you end up with very little usable throttle travel, and kind of crap control because of it. Controllers that vary current based on throttle are much more usable, but, unfortunately, most controllers don't support this. Nicer ones might, and will specify if they do.

>>1208094
That's great! I was thinking of re-fitting my current 700c road bike (steel forks and alum frame) with a front hub 500W motor. Any suggestions on inexpensive brands? I'm in grad school for EE currently and don't want to spend too much. I was considering designing the controller from scratch using an arduino and an inverter as well. Not sure if that is too much to take on by myself.

>>1208094

(cont.)

If you're building your own controller, however, obviously you can put that in yourself. I've also considered making my own controller, because there are a few features I would like that are only present on more expensive models. Have a look at ebikes.ca's controllers. It's a bit pricey, but it has a very robust feature set, and includes most everything I'd be looking to do myself.

Speed limiter would be a good idea, specifically for legal reasons, and doubly so if the motor drives through the gears.

Never much cared for pedal assist, but I'm a lazy fuck. Straightforward enough to put a couple load cells on the pedals (though they necessitate some sliding contacts) or a torque sensor on the crank (probably requires some modifications to the frame). Not necessarily easy without the right equipment, though.

Misc stuff: Ball bearing disc brakes are choice. Braided cable sleeving and adhesive-lined shrink tube on the wiring is cheap and will make the finished product look very clean. Wear a helmet...I've eaten shit, pretty bad, twice on mine (one time just left scrapes and bruises and potato-chipped my front wheel, the other cracked a rib). Anderson powerpoles are a loose "standard" connector to use.

And expect to spend more than you think you will. I got a good deal on all my parts (especially the batteries), and, all-up, I'm still sitting on about $1000 of equipment, including the bike itself. Prices have come down a bit since I got this stuff, but still.

>>1208110

Hunt ebay or craigslist for a motor, IMO. They're common enough that it's pretty easy to find them at a good price. Non-geared hubs are basically bulletproof, long as you don't overheat them.

Not a fan of the front hub, as it affects steering more than rear hub. It's not awful, though; one of my bikes had a front hub, never really caused problems. Definitely preferable to use a front hub if the batteries are mounted on a rear rack, to keep the thing more balanced.

Also, I forgot: Even if you have steel drops, I'd recommend a torque arm or two to keep load off them. They're not expensive (I know of at least one guy who just used a couple box wrenches pipe-clamped to the forks and it worked fine), and having a hub tear itself out of the drops can be catastrophic. Admittedly not that likely with a 500W hub, but still.


Wouldn't use an inverter for the controller (although I may not be thinking of the same thing you are, as "inverter" is a somewhat vague term). There isn't much in there you can repurpose, and the power stage of a 3-phase BLDC controller is just three full H-bridges. Might be more effort to try and hack in your own controls than just do it all yourself. Designing your own from scratch also allows better component selection; most inverters are specced to handle more voltage than an ebike runs at, and less current.

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>>1208120
Thanks for the /adv/.

I too have eaten my fair share of shit on a regular bike alone and have been hit by a car going 20mph (my own fault). Nothing broken surprisingly, just a thrashed bike and some major bruising.

I'd like to build my own li-ion cell with a BMS because it think it would save at least $100. It would still be expensive but worth it, I'm hoping. I also have access to a 3-D printer to house the battery and components so it's looks nice. However, theft is also a concerning issue. I need to do a little more research but I'm assuming most hub motors are 3-phase.

I'd like to try something other than a torque sensor because the ones I've seen are expensive. I also didn't care for the 1-2 sec delay for the motor to kick in while pedaling or hitting the throttle.

Here's a pic of the bike I'd like to convert. Also, could I add disc brakes to this bike and why are they choice?

>>1208064
Speaking from over a decade of experience I can assure you that if all you're doing is commuting then you DO NOT want a hub motor.

To this day they have a piss poor efficiency band.

You want a mid-drive kit so that you have the ability to shift around your gear set to stay in that efficiency band.

Personally I run the Bafang BBS02 as my everyday commuter. It's a 750 watt motor and is the smallest possible form factor you can pack that power into.

750 is even too much power for me since my commutes are all pretty much flat with very little incline. I could get away with the BBS01 which is 350watts and it would still get me around just fine.

You may think that the idea of tinkering around with all the parts, and fidgeting this controller and tweaking that, and getting this just right SOUNDS fun, but it gets freaking old freaking fast.

Additionally the price of the Bafang kits might sound expensive, compared to the relatively 'cheaper' 500 watt hub motors you can get from ebay or the like, in the end it all balances out after you drop cash kludging all the pieces you need to buy together to get you 500w hub motor fully functional.

In the end I have found it is infinitely easier and ultimately cheaper to buy the kit than to piecemeal your own solution especially when it comes to commuting.

That being said, I do have a fat bike with dual 2,000 watt hub motors for maximum fun which is absolutely bitching.

There was a friend in my uni that using an brushless motor powered the rear whell of a bike, like, you know, every bike, and via pwm controlled the speed. It didn't look like something very hard but it was expensive. Maybe you could use that as a starting point.

>>1208139
>I'd like to build my own li-ion cell with a BMS because it think it would save at least $100. It would still be expensive but worth it, I'm hoping.

Honestly, the only advantage to building your own pack is if you need to meet some dimensional constraint (such as me fitting it in into the small mid-frame gap of a cantilever-suspension MTB) or you want to use some specific cell. I had to build a spot welder and hassle with encasing it, mounting, wiring, etc. If I could have gotten a ready-made battery at near the price I paid for the cells (admittedly would have been a little difficult), I would have definitely gone for the turnkey solution.

Already had a pair of BMSs from two much older packs that died.

Not much you can do about theft, beyond locking it up good like you would with a normal bike. I used to have the pack removable, as that made up the majority of the cost of the bike. Figured if it got stolen without the battery, I wasn't completely boned. I also considered an interlock that shorted the motor windings out when the battery was removed. This way, any thief would quickly discover it was permanently in brake mode, and hopefully give up. Not effective if they just pick it up and throw it in the back of a truck, but it's something. Forgot about hassling all that since, now, I can just lock it up in a safe room at work.

>I'm assuming most hub motors are 3-phase.

They're all either brushed or 3-phase DC. You can, of course, run them on an approximated or true sine wave for extra smoothness, but eh...not that big a deal (even less so for geared setups)

>could I add disc brakes to this bike and why are they choice?

No, unfortunately. You need mounting tabs on the forks to be able to install discs. Disc brakes allow for better brake modulation and more reliable braking power. Ball bearing (or hydraulic) calipers further improve that. You _could_ weld tabs on, but IDK about those forks. Usually, you want them beefier (like downhill MTB forks).

>>1208064
Yup. Buy a good lithium pack. Prolly 10ah or 20ah depending on your need.

Buy chinkshit china REAR wheel drive 48v 1,000 watt hub motor and controller kit off ebay for ~$300.

Carefully inspect shitty plugs and wires or consider bypassing olugs and hardwire it all oer directions.

Haul dick.

My 250 pound ass had lead batts and could near hit 30mph. No oeddling required.

Will be almost 1,000 bucks but you wont find a better ride.

Invest in a good lock and gos tracker for fuckwits that rob your shit

>>1208223
BRO...

PLEASE GOD POST 2K BIKE AMD ADVICE FOR POWER.

BEEN HAVING HELL BREAKING 1,000 WATTS WITHOUT BREAKING BANK.

PLEASE EXPLAIN YAR SHIT... POST PICS

sorry op. Not trying to jack your thread bit this has been bothering me a long minute.

Im also currently trying to buy a spot welder to build packs and if i do i will build wtf ever saze and pack u need at whatever parts cost u want. Or will weld tabs for u or whatever.

>>1208223
Also anon. After looking at the kansas laws i realise that a 750 watt ebike is legal. I recently got a dui and deoending on how things go i may lose my liscense for a bit and work 5 miles away on a highway. My fat ass is 250 pounds. Mostly gradual hill terrain on a highway.

Would a 20ah or 40ah get me to work with little to no pedling?