First ebike, Controller and computer questions

Hi, I'm James. I've been toying with idea of converting my bike into an E-bike for a while now. I used to be hugely into cycling until i got my car and became a bit lazy (and living on the coast i'm not a huge fan of battling the wind on my own), so it just sits in the corner collecting dust in between the rare sunny weekends in the UK. I would quite like to ditch my 20 mile,£7 a day commute habit for something a bit cheaper and healthier.

I work in engineering and DIY projects aren't alien to me. I want to build a mid drive kit, (don't fancy molesting my hope wheels) with a 250watt 36v brushed motor, pedal assist only, Going to start with a 36v 12Ah battery built from 18650's and an integrated BMS. I have no problem mounting the motor or building the battery.

I have seen the ktlcd3 Computer and would really like to use it, I'm having trouble finding a compatible controller unit, not just with the computer but compatible for brushed motors also.

Any help and or replies are much appreciated

Thanks

http://www.pswpower.com/peng/pic.asp

KT-controllers and their displays aren't suitable for brushed motors. You were thinking of a kit like this?
https://www.amazon.com/gp/product/B01CL2NWUY/ref=as_at/?creativeASIN=B01CL2NWUY&linkCode=w61&imprToken=yRmOxAB2EYiYxsG2qx3Llw&slotNum=0&ie=UTF8&psc=1
Overpriced, in my opinion, and it doesn't support pedal assist. For a little more, you can get into TSD-Z2.

That's the motor I wanted to use for ease of mounting and cheap enough to upgrade or replace (If necessary) . That's pretty much the image I've had in my head.I can get that motor in the UK for about £60.

Its not so much the display i want, just the ability to program a max speed of 15.5 and to have pedal assist only. The laws in the UK dictate this is all we can have, if this was just an off road toy then I would go mad with a massive motor ect. Since I want to use it for commuting i would like to keep it legal.

I would rather not buy a kit that replaces my bottom bracket and I don't want to pile a load of money in to a kit I would stand less chance of repairing myself (if it went wrong).

I'm feeling like my only options are to use a brushless motor (which I cant find in the spec I want) or run it illegally (which could jeopardize my driving license if caught).

Well, I'm not sure where you're going, but you want a brushed controller that has pedal assist. That spec might be tough to buy off the shelf. Those controllers use throttles.

Someone here recently posted an Arduino PAS module that converted the PAS pulses to a DC voltage level, which you could use to feed the throttle input of those cheap brushed controllers. Maybe he will sell you a prototype.

Or this is in your neighborhood. Maybe this thread will help. No speed limit, but maybe you can run on 24V and set your gearing to max out at 15 mph.
http://www.pedelecs.co.uk/forum/threads/yi-yun-brushed-motor-controller-on-my-powabyke.19791/

I'm feeling like this will be more trouble than it's worth to me considering i'm loosing out the efficiency and control-ability of a brushless motor. Was wondering if I could just use a rectifier (in the same way mains is converted to dc, just with 6 diodes).

Thank you for your advice, it is appreciated. Ive had a look at the 250w GSM kit, allows me to use my own controller, a lot cheaper than a bafang and from what i've read people are reporting outputs of up to 900watts.

So, don't molest your Hope wheels. Just remove one and use a small low powered 250w rear gear hub with the appropriate electronics to limit your speed. The Hope wheel can sit somewhere unmolested collecting dust as it is now. :^)

And heck, if you use something small like the Xiongda YTW-06, and build the bike carefully, you can make it nearly impossible for all but the most astute observers to even know that you have electric power on tap. And in that case maybe creeping a bit past the 15.5 mph limit wouldn't really be risky at all since it would be tough to tell that you weren't a regular cyclist. Heck - hook it all up to some not-so-keen looking second hand bike and you'll be essentially invisible at speeds below 20 mph. Wear a tweed jacket with elbow patches to complete the camo.

https://endless-sphere.com/forums/viewtopic.php?t=93087
https://endless-sphere.com/forums/viewtopic.php?f=6&t=91309
https://endless-sphere.com/forums/viewtopic.php?f=3&t=49691

But if you are truly dead set against a hub motor, search this forum for people who have re-purposed hub motors as mid-drives. That way you can use the conventional controllers. Also, consider maybe using a Cycle Analyst for your control purposes to keep you legal or to selectively allow you to tune the bike to be illegal.

https://endless-sphere.com/forums/viewtopic.php?f=28&t=45245&hilit=convert+hub+mid+drive