Building an EV more efficient than walking

[Saladin]

Brake upgrades...the second most important part after tyres and oft ignored in the world of DIY conversions.

I like a 203mm rotor. It's torque-y and the right side of too big to draw too much attention or become an incidental impact liability. 220mms can be overpowered for a light rider on a light bike and you can get wheel-locking issues.

The original owner and converter didn't clamp the motor in place...
I went about rectifying that and realised the next problem.

The bike has an oversize bottom bracket tube, that needed to be slieved to accept the motor spindle. Original owner did that with pressed roller bearings.



Ok so the Bafang locknut couldn't bite the frame because of the larger BB ID it was pressed into the cage of the roller bearing. This meant if I do clamp the motor it would break loose smashing into the brake line on the downtube, and pincing the hose to disable the rear brake...

The fix the owner used was to not lock the motor and when you depowered it it would fall back down on the BB and the brakes would start working again. So simple! Fantastic!

This is what the brake hose looked like after 500km of that craic...



I'm impressed how robust they are.

This is a torque arm required situation.



Custom fabrication, using the original Bafang locknut, with an inner tube frame protecting, damper slieve.

See how that works?

[Saladin]

The original brake pads were expired, the dot 4 was passed it's best before, I stripped the refill port screwhead trying to open it and I had a very sorry looking rear brake hose. ...What's that? Quad piston Shimano's on sale?



Boom!





Change the calliper spacers, mount the callipers, change the rotors, run the lines, mount the levers, bleed the system. Simples.

203mm front and 180mm rear. I rather not undersize the rear rotor but a 203mm won't clear the chainstay.
A lottov bike builders put smaller rotors on the rear because it's ony 30% of your stopping power... ...I don't understand how it should warrant a lower spec by that logic...besides I use the rear for steering more often than stopping.

For all my other bikes I just upgraded the rotors and pads and renewed the hydraulic fluid. My hardtail eMTB has more stopping power due to it's lighter weight & sintered pads despite only having dual piston tektros.

Fun bike for a 6th bike.
If I could only have one I'd stick to the hardtail. It's more efficient, discrete, better at everything above 0°C, tyres cost two thirds less and there's more options & the big one: suspension; it's got better road holding.

I might go tubeless on the fat tyres with a magic puncture fixing potion inside the tyres if the new tyres are getting penetrated. I can't help but notice the best tyres I could get affordly have a lower puncture protection rating than my hardtail and aboot 3 times the contact patch...

[Saladin]

I take it back. Hohoho...new favourite boike! after 500kms..
Handles a lot like a motorbike, loves to lean and be counter-steered.
Once I put aside my intrinsic desire to bomb it downhill. It's an astoundingly capable machine...just not at this..




Roughly 30W per km...not massively far from my hardtail annabout 5kmph slower.

I'm coming around to the no suspension thing...it's lower maintainence and more reliable...and not for bombin' it...
Suspension seat is a nice compliment to air volume.

Only one puncture so far on the new twice as nobbly Winter tyres; kindov deserved it...I was ploughin' through thorny scrub on a disused forest track.

What it can do that the rest can't is climb a 45° hardcore loose pack forest fire break and get to places like this...



and this



I've named her Sherpa

[Saladin]

Honourable mention accessory is this lighting kit.



2 high output front lights with horizontally shuttered dipped beam optical projection. Perfect for road use. Mentally bright, very punchy. I'd still recommend a lid lamp though because we do often need to point the bike one way and the head tuther. Funny how on a bike you go where you look and without a lid lamp you have to look into the pitch night and go there until the front of the bike turns to meet it.

The lighting kit plugs into the bafang harness on slim waterproof connectors.

The tail light is a combined indicator/hazard lamp/ brake light & tail light.

Each front lamp has an integrated horn too..they're right obnoxious when you go stereo!

Used bike with questionably installed kit, carrier & spare tube: €700
Collection/delivery €100
Brakes: €80
Tyres: :€120
Bars: €45
Grips: €30
Seatpost Adapter: €15
Linkglide Groupset + 11spd Chain: €120
Lighting kit: €80
Replacement Thru-Axle: €50 ( because Cannondale!!)
Replacement Derailleur Hanger: €25 ( because Cannondale!!)
Better Display: €80
Half-Twist Throttle: €20
Gear-Shift Sensor: €20
89mm Crank Arms: €30
100mm Stem Riser: €15 (geometry compensation for shortened cranks)
Mudguard: €15 (bought one, made one...still a mite undersized..)
Kickstand: €15 (undersprung rattly shyte and already broken)

Bar Mirror: {€10: Adapted a LHS from the spares bin}
Suspension Seatpost + spring saddle: {€110: One fits fleet}

€1560

I'm running dual batteries and replacing the 48V 24Ah one she came with for a 52V 30Ah triangle.

You can pair a 48v and a 52V across a battery combiner (dual ideal-diode). They cascade discharge which mean it's not really parrallel it's sequential with overlap and the higher voltage battery will probably trip LVD on it's internal BMS before you get home.


Your mission should you choose to accept it; find a(n electively restricted for off-road use) store-bought machine with a 1kWh non-proprietary battery, a 160Nm torque programmable motor that's transferable to another bicycle, quad piston 203/180mm hydraulic brakes, a replaceable steel groupset with a rivetted casette & an e-bike rated chain. Nobbly Winter tyres and a comprehensive lighting package for oh..less than €5k...! Good hunting!

If I do 15 000km a year at 30watt-hour per km.
that's 450kWh per yer transport fuel.
One quater of that is import: 113kWh x €0.40 = €45 per year transport fuel cost.

+ a €30 chain (varies) every ~ 1200km (€375)
a rear tyre every ~ 3000km (~€125)
a front tyre every ~ 10 000km (~€42)
20L of chain degreaser annually (~€200)
2L of chain lube annually (~ €100)
a new cassette every ~5000km (€90)
Wheel hub bearings...vary whenever they get crunchy..: every 10 000km?.. depends on seals and riding conditions

Annual cost of ownership:
Ballpark €0.07 per km.


With a heavy bias on off road. I hardly ever come home without gravel grit and/or mud in my drivetrain...having tortured my tyres scrambling over coarse hardcore.

Funny thing about car ownership; is that costs money when they're not moving too.
Has anyone ever gotten an insurance refund or a tax rebate for the days they didn't drive?
Besides; if I can't fix it I don't own it, I'm just renting.

[Saladin]

Here's a few mods to help.
4.2V x 14cells series = too bleedin' high with no bejaysusin' overhead..



and I'd rather 2000 cycles to 85% SOC rather than 500 to 100%




Derate!!!!!!!!

See that potentiometer that says VR1 for voltage regulator 1?



Twiddle it until it outputs 4.1V per cell.



Presto that batteries "lost" 15% usable but it'll last 4 times longer and it's waaay less likely to burn your house down.

There's another way to mod. this externally.
My most recent battery charger didn't have that very convenient turny trimpot. I used the series Vf drop of a bridge rectifier instead.



Charger positive out connected to DC- with DC+ output feeding the battery charge port positive.

Something like this with the middle two legs not wired.



Marmalade it onto a lump of copper or aluminium. If it runs for 30mins at full load and touching it doesn't burn your finger then the heatsink is the right size.
The higher the Vf the better for this application, which is a lower-end pocket friendly type, in this case as we're aiming for a float current voltage drop aggregate of 1.4V at 58.8V.
The charger charge complete green LED even still works...I'm guessing that's driven by opposing voltage tail current threshold.
Sure! You can just use two or more series diodes instead.

[Saladin]

...

[Saladin]

It's been a while...

...lots of catching up to do...some will have to wait because I'll have to dig out some bits for story-tellin' pics.

I'm still an advocate of the BBSHD foremost for converting bikes. They are massively upgradeable. Unfortunately Bafang decided to destroy the product by switching the communication protocol to CANbus which is no longer user programmable and has a 60kmph speed restriction.

The older UART versions are still about. They're the ones that use displays with this connector.



Bafang are still making UART motor controllers so you can always buy a CANbus motor, throw the motor controller in the bin and fit a UART replacement..sigh...recommendations like that oughta be a red flag eh...

By all accounts everyone who has experience with UART versions hate the CANbus move.



Risunmotor are still selling the UARTs

I came across Daniel Nielson's firmware for the old motor controllers and it's a worthy upgrade.

We now have access to:

A bit more power without hardware modifications! (max 33A).
No upper voltage limit in software, can by default run up to 63V (maximum rating of components).
Support lower voltage cutoff for use with e.g. 36V battery.
Smooth Throttle/PAS override.
Optional separate set of street legal & offroad assist levels which can be toggled by a key combination.
Support setting road speed limit per assist level.
Support setting cadence limit per assist level.
Support cruise assist levels (i.e. motor power without pedal or throttle input).
Thermal limiting gradual ramp down.
Low voltage gradual ramp down.
Voltage calibration for accurate LVC and low voltage ramp down.
Display motor/controller temperature on standard display.
Use of speed sensor is optional.

Here's the street & off road settings I've tuned for my BBS02's "750W"

{Right click -> Open in new tab for Zoom}







..now producing 1250W @52volt with motor high temperature rollback.

80°C = 100% motor power
85°C = 50% motor power
>90°C = 10% motor power

I now have a Motor Temperature display in the display "range" field that was hitherto next to useless due to the absurd level of inaccuracy as a battery discharge rate predictor. Excellent feature too!

Installing the firmware is a wee bit technical.
Donations to the developer can be sent here.

[Saladin]

After the cargo bit came. Sherpa the fat tyre (best climber).

Sablo materialised on the frame of a Medium sized 29" Hardtail Cannondale Trail.



I tried shunt-modding her for 50% more powah.

It's pretty tough and twould seem that my All-the-Power-All-the-Time tuning wasn't compatible with the stock FET Tolerences running 50Amps.

If you solder another resistor to the current sense circuit 100% power measured = 150% actual.





It's a very difficult mod.
You have to remove the PCB from the housing without breaking it.
Dig out the potting compound. Hack the hardware.
& then put it all back together again.

I broke two motor controllers with corrosive silicon sealant.



Two with mechanical damage.
and the one successful one I blew a FET after ~150kms and after amputating the wounded semiconductor I have an "over-clocked" 2.5 phase motor...

...all of which cost me the equivalent to ~ 500kms of petrol or a training course on electronic "repair"..

3.5 horse power hardtail is totally worth it.
...ahem..but...know when yer beat eh..
So next up to bat is a BAC 855 external controller that allows me to Ctrl+X the stock controller and send her to 2.5kW at 52volt or 4kW at 72V.

Inspired by High Voltage



This is in the pipeline.

[Saladin]

I had notions of getting a full suspension enduro bike to handle all the power I'm about to invest in.

The problem is most full sus. frames are pretty hard to squeeze 4kWh onto for my prefered range at my preferred load.
Aero's a killer above 35kmph.



The Cargo bike is still my fastest. It's got the best aero. hands down and room for my full 7kWh of bike battery modules. +5kmph than the rest with ease. She also holds the highest top speed record, which is gravity assisted. She cheated and took an extra 20kg to the trial.
I did a 300km round trip on it yesterday to look at an Enduro bike.

The thing was ragged out and the replaced rear wheel was junk so I didn't buy it. I don't think there's a cheap option for a modern full-sus.
Either pony up or pull every bearing and rebuild the shocks...either way it's a fair bittov effort to land one. And then you can expect to service the shocks every 50 hours of use or 10 in the wet if they're air springs...

It would seem that the used mountain bikes you buy from city dwellers tend to be in much better knick than the ones you get from mountain dwellers...go figure...

Unless a 29er with a coil springs and enough room for 15kg of battery shows up on classifieds for reasonable money...
...I might haveta crowd source a stealth lecky dirt scrambler for education porpoises...

I'll prolly just put more batteries on my already rebuilt XC full sus.



Starting with a seatpost carrier +1kWh.

That or I'll sell it to leverage a bigger, badder, burlier bike.