First e-bike build - rear hub motor - 35mph+ - LiPo

Hello.

I'd like to build something on a budget the lowest the better. Best value for money preferably.

I live in UK and will cycle mostly around very small town. It lays its half on a small incline of about %15.

Id just like to cycle around without worring about potholes and taking park / grass shortcuts.

Couse of that I believe full sus will be a way to go but as the budget is tight I may start with hardtail.

Second hand Scott Scale 770 27.5" is on my mind.

I did research motor choices and as I would love the bafang bbshd in the future I will stick to some direct drive rear or geared hub as my first ebike ever.

The town have horrific congestion around rush hours so Id like to be able to skip the traffic. Most roads are 30mph max but I will be using 40mph ones from time to time as well.

TLR

Like to be able to top 40mph+ not pedalling much. On regular basis 30mph+ without assist. Throttle only preferably. Would like to do like 20 - 30miles range.

I will be cycling around home not further than 5miles away so I think that smaller batteries will be a way to go so I can just swap them when I am out of juice and charge them overnight. Will go for LiPos which will sit in a bag mount under saddle.
Was looking at these Multistar High Capacity 20000mAh 6S 10C Multi-Rotor Lipo Pack.

CycleAnalyst is what I'd like to have to monitor and adjustments. At some point would like to use switch to change mode to like 15mph max just in case


I figured out this setup - what you recon?
* MAC motor
* 72v controller
* 20Ah 18S3P 66.6V Lipo
* CycleAnalyst v3

What should I buy in your humble opinion? Im based in UK.


Thanks for all your help!

Hey there.

Ive just built something similar and being from Scotland I am super tight!

I picked up a Big Hit 2 DH bike for £150 off ebay, then got one of the cheap 1000w chinese hub motor kits for £120 (special offer at Christmas) with the LCD Screen.
Ive banged that on with just 2 6s 10,000mah multistar batteries robbed from my mapping hexacopter (so only really about 45v and they are a bit knackered) and I can get 45kmh out of it, with quite a reasonable range.

Thats with my 120kg fat gittishness onboard too.

Ill be upgrading with another 6s pack shortly and fitting a better controller, along with modding the motors phase wires and cooling.

Budget doesnt need to mean cack. DH bikes are definetely the way to go!
I use mine around Warrington and its brilliant for cutting through all the traffic.

Thanks for your input!

I can't decide between decent like 2 years old hardtail like that scott select 650b or trek superfly 5.
Not sure if 10 years old DH bike will be better having full suspension?
Also I am in doubt now about going straight into 66V 18S3P or sticking for a while with 48V 12S2P?

Could you provide link to that motor?
Im browsing ebay but cant find any kit with 27.5" or 29" wheel build.

And for a start - how badly do I need CycleAnalyst?

Thanks!

https://www.ebay.co.uk/itm/36V-1000W-48V-1200W-Front-Wheel-Ebike-Conversion-Kit-with-Sine-Wave-Controller/332136139653?hash=item4d54db4b85:m:mC755DP8cOus5JjbNzB4ygA

not the seller i bought from but the same wheel. Alot more expensive though for the sake of having a ready made wheel. Youd be better buying a cheap 26" kit and relacing it onto a 29" rim if your particuarly wanting a 29er. Bear in mind yourll lose a fair bit of torque *roughly 10.4% depending on your tyre choice etc* and its torque that i find wanting on my build at 26".

Personally i would go with a 48v system as its your first and then just upgrade the kit to 72v later? That way you get used to it etc?

Not sure about the analyst thing, I know i dont have one. Mergh... im sure its great etc but i just dont think i need it at this stage.

Buy yourself a cheap imax clone charger *about £15 with the inbuilt power supply*, some lipos, bang them in a rucksack with a 1m long set of decent cables, xt90 connectors so if you fall off it will disconnect and bobs your uncle.

With the bike, i found id be much happier stripping an old bike down and throwing bits away from something that was cheap than some fancy all singing fancy bike. It might be a kilo or two lighter, but just eat less pies. Besides, pedalling something heavier gets you fitter. Isnt that the point of a bike?

I reckon build a "cheap" one first then build a fancier second bike with all the info you gain from your first build. Half the bits can be transferred onto the second one.

Was thinking about going that route just didnt find out yet how much can cost relacing a wheel. Any number on your mind?

Im not sure about 48V I mean I can agree thats a good starting point but a bit waste of money? I cant later use that packs to make up 72V as they will be degraded? Dont you think?

Relacing should only be 30 - 40 quid. Its not a hard job. If your patient you can do it yourself (hey its a good skill to learn)

2 off 6s packs can be complimented by a 3rd after a few months. How many times are you going to have used it?!!!
call it 50 timess. Thats nothing. Will be no notable difference in the life of the cells. Unless you have abused them.

The cycle analyst thing will help you to prevent that as you can preprogram certain conditions so it shuts off (i think?)

6s multistar 10,000 mah batteries are about £80 from hobbyking at the minute? (might be less as i think there was a special offer) start with 2 of them, then add a 3d to make it 18s in total.
Then you can add another 3 if required to double up to 20,000 mah

do bear in mind that cheap rc lipos have no BMS so its entirely manual.

You could add a bms system if you wanted, (very easy and cheap to do) alternatively you could build your own pack from 18650 cells. Ive just build a large pack for my campervan to run the ancilleries (induction stove, heater, lights etc) all very easy to do.

For starters, you will quickly fry a mac if you run it on enough volts to go 40 mph. So you want a direct drive motor. Good one best, one with a larger magnet, more copper, etc. Heavy motor. Those often come in a kit with 72v controller.

But the poor mans 40 mph bike is pretty easy. Cheap ass 1000w kit with direct drive hub. this motor can take 2000w easy. For a short ride, as you describe, it can do 3000w.

Then get a new controller for it, 72volts, 40 amps. that's the 3000w. volts x amps gets you peak watts for a controller.

It will do your 40 mph briefly, and maintain a 35 mph cruise till your battery dies. RC lipo like you plan, but 20 cells in series. Ideally 8 of them, 5s 50000 mha. That gives you 72v 10 amp hours, and it will die just before your motor melts. Go no bigger. 18s will work with a 72v controller, but you won't really hit 40 anymore. 35 or so.

Smaller can work, but it beats the hell out of batteries. I don't recommend as small as 5ah, even if the rides are very short.

26 inch wheel too bro. if your bike has disc rear brake, just slap on a 26" wheel and a fatter tire. Otherwise, different bike.

Don't hit potholes at 40 mph with hardtail. 40 mph with the rear wheel a foot off the ground is pretty exiting.

Lastly, but first in importance, you need two very good torque arms for a high power motor. Often this means fabricating a good torque plate that fits best on an individual bike. The cheap kits won't come with them.

Thank you guys!

I will go with two of these for a starter: 6S 20mAh 10C

https://hobbyking.com/en_us/multistar-high-capacity-6s-20000mah-multi-rotor-lipo-pack.html?countrycode=GB&gclid=Cj0KCQiA-qDTBRD-ARIsAJ_10yLwU6Owzj8XKZw00gm-q4r-RyDTo0UrPeQTxpIM01AhWS3XN87xw-kaAsVUEALw_wcB&gclsrc=aw.ds&___store=en_us

1. Can I run 12S2P 44.4V with 36V controller or should I use 52V controller?
2. What controller is more suitable for 18S3P 66.6V - 72V or 52V controller?
3. I have turnigy quattro hooked up with 500W psu so I can balance charge each pack separately.
4. What particular BMS should I use with 12S2P 44V or/and 18S3P 66V?

Getting nice deal on a bike just now will post pictures soon.